US3297041A - Tobacco smoke filter or the like - Google Patents

Description

Jan. 10, 1967 R. C. SPROULL ETAL TOBACCO SMOKE FILTER OR THE LIKE PULP STORAGE Filed March BINDER STORAGE TRANSFER.

CONVEYOR.

FEED CONTROL MILL CONVEYOR.

COLLECTOR TRANSFER PROCESS COOL CUT

TRANSPORT F: J. E- E INVENTORS REA V/S C SPROULL RICHARD M. BERGER JOHN B. L YNC H ATTORNEYS United States Patent Ofifi ce attain Patented Jan. to, 1967 3,297,041 TOBAGCO SMOKE FILTER QR THE LlKE Reavis C. Sproull, Richard M. Berger, and John B. Lynch,

Richmond, Va., assignors to American Filtrona Corporation, a corporation of New York Filed Mar. 15, 1965, Ser. No. 439,531 16 Claims. (Cl. 131-466) This application is a continuation-in-part of our earlier application of the same title, Serial No. 230,981 filed October 16, 1962, now abandoned.

This invention relates to filters, and particularly to low density filters comprising in substantial part, natural fibers, as opposed to synthetic fibers.

Filters constructed in accordance herewith, find particular utility when used for the filtration of smoke, as cigarette filters, cigar filters, or the like. However, it is to be understood that While the term filter is used herein to describe the product hereof, and While such product finds particular utility in the aforesaid applications, the product can be put to various other uses where filtertype components in suitably adapted forms and shapes serve a desired function other than smoke filtration. Notwithstanding the various uses which may be made of the product provided hereby, since the same finds particular utility as a smoke filter, the invention is described hereinbelow as a smoke filter, and its relation to the prior art is similarly so considered.

The conventional smoke filters now in widespread use and predominantly incorporated in cigarettes of the socalled filter tip type are synthetic fibers, and usually cellulose acetate fibers. Normally, such synthetic fibers are stretched and crirnped by various processes conventional in the art, and then are formed into a tow wherein the fibers are randomly oriented primarily in a longitudinal direction. Bonding of the fibers within a tow is customarily achieved by impregnating the tow fibers with a compatible synthetic plasticizer and subsequently curing the tow either in continuous form, or as cut into individual segments. While filters formed in accordance with the technique described in this paragraph have met with widespread commercial success, and are in Widespread use today, the use of synthetic materials necessarily results in certain expense for raw material and/ or partly processed materials, and there are limitations on the taste qualities of the final product. Moreover, the efiiciency of synthetic materials, insofar as sorption is concerned, is limited and a comparatively substantial quantity of synthetic material is required to provide any satisfactory degree of filtration.

To increase the etficiency and reduce the cost of smoke filters, various prior workers in the art have considered the possibility of utilizing natural fibers in some form. First, there have been suggestions with respect to forming a smoke filter predominantly from synthetic fibers, in accordance with the processes referred to above, but in corporating in such a filter, a comparatively minor portion of a natural fiber, such as cotton, wool, or the like. Secondly, it has been suggested, for example, to provide a synthetic fiber filter having cork particles or the like randomly dispersed therein. Although suggestions along all these lines result in some reduction in cost possibly, at least insofar as the raw materials are concerned, the filter is still predominantly formed of synthetic materials,

and the sorption and taste qualities of the synthetic materials necessarily impose certain limitations on the filtering properties.

Possibly appreciating the disadvantages and limitations on filter components formed predominantly from synthetic fibers and materials, there have been prior suggestions as to the use of natural fibers, or the provision of filter components comprising primarily natural fibers. One basic construction along these lines contemplates using merely a cotton wad, but here the uniformity of the product is poor and the necessary method of manufacture is inherently slow. In accordance with another prior suggestion, natural fibers, preferably wood or pulp fibers of so-called short length are used with a binding agent. The pulp or wood fibers are somewhat randomly dispersed or disposed in the ultimate filter element and bound together by the binding agent which is synthetic and either in the form of fibers, or powder. In accord ance with this suggestion, the idea is to form the fibers into a mat by a suction depositing technique, and to either simultaneously suction deposit therewith bonding fibers or impregnate the fiber mat with a bonding agent to achieve a suificiently stable element. While the basic suggestions appear to have merit, products formed in accordance with this general technique as suggested in the prior art, have not proved satisfactory in operation. More specifically, following this technique does not insure uniformity of heterogeneity in fiber and bonding agent and the technique at best results in either a product which possesses sufiicient hardness, but an excessive resistance to draw, or a satisfactory resistance to draw, but insufficient hardness.

Following the natural fiber filter suggestion discussed in the preceding paragraph, and in apparent recognition of the problems encountered in connection therewith, workers concerned with the provision of a suitable filter element from natural fibers attempted to obtain some coherence from the fibers themselves by utilizing an interlocking type relation therebetween as opposed to rely'ng solely or primarily on a bonding agent. Specifically, the later workers in the art along the lines here in question considered forming the filter element from fibers of the type comprising a bundle of fibrils, and using the curly nature of the fibrils to achieve at least a substantial coherence between the base fibers themselves, thus eliminating at least the amount of binder required, and preferably any binder whatsoever. Here again, however, the teaching was to use a curable synthetic resin binder deposited on, or impregnated in the mat or mass of base fibers, if desired, to achieve a greater hardness. In carrying out this suggestion, it was found that the operational problems were generally the same as those faced in connection with the prior natural fiber-type filters.

With respect to the use of a bindng agent or binder in connection with natural fiber filter elements, prior workers in the art have generally followed the basic techniques utilized in connection with synthetic fiber filter elements i.e., they have suggested that the binding agent may be added as a solution, as a binding type fiber, and/or as a dry powder, by mixing with the base fiber a sufiicient amount of the binder in a conventional way, such as spraying, simultaneous suction depositing, or immersion. The teaching has been with natural fiber, as with the synthetic fibers, that as long as the binding holds the base fibers of the ultimate unit in position, a desirable ultimate product can be obtained. Such prior teachings, however, as suggested above, do not yield a satisfactory ultimate natural fiber product at least, and thus synthetic fiber filters remain in widespread commercial use notwithstanding their cost.

Bearing in mind the foregoing development in the art, the present invention has as its primary object the pro vision of an inexpensive filter element formed from natural fibers and possessing characteristics which render the same suitable for ultimate use as an efficient and efiective smoke filter. Consistent with this object, a further object hereof is to provide a filter element formed predominantly from natural fibers which is not subject to the disadvantages previously existent in connect' on with filter elements formed from such fibers. Still further, a primary object of the present invention is to provide a filter element formed at least predominantly from natural fibers, yet which is at least as efficient, if not more efi rcient than filter elements of the type previously formed from synthetic fibers. Still another object of the present invention is to provide a filter element conforming with the preceding objects which can be formed with economically feasible techniques, and which incorporates natural fibers of minimum costs, such as for example, wood fibers or pulp fibers. Yet another important object hereof is to provide a smoke filter which improves the taste properties of the final product. A still further object of the instant invention is the provision of a smoke filter of the type described which incorporates a minor proportion of one or a combination of additives to provide certain specific properties or characteristics to the structure.

The foregoing are but basic objects of the invention, and possibly a list of specific objects could be here set forth. However, these specific objects will become apparent to those of ordinary skill in the art after considering the following detailed discussion of the instant discovery, and accordingly attention will now be directed to the basic aspects of the same.

We have discovered that ,in order to provide a satisfactory smoke filter from natural fibers the same must possess certain correlated physical properties and structural characteristics which differentiate the same from prior art constructions. Specifically, we have discovered that the problems encountered with prior art suggestions result from the lack of uniform heterogeneity of the product in substantially all directions, and from either the excess of bonding material within the final product, or from the existence therein of a continuous phase of binding agent in a greater concentration than the concentration of binding agent in other phases of the final product. These factors can possibly bebetter understood by way of specific example Assume, consistent with the prior art teachings, that natural fibers are deposited in mat form, and that thereafter the mat is immersed so as to impregnate the mat with a binding agent. In this instance, the base fibers of the final product become substantially all covered with a binding agent, and there is little, if any, surface area of the base fibers which is directly exposed. While proper bonding may be achieved with the immersion technique, there is an excess of binding agent which limits the exposed surface area of the base fibers, and limiting of the exposed surface area of the base fibers results in an inefiicient final product. Assume, on the other hand, that the final mat formed of the base fibers is sprayed with a liquid, or that a powder layer is deposited thereon. In this instance, if the excess of binding agent or material is eliminated, then the face of the mat which is subjected to the spray or depositing operation carries a continuous phase of binding agent in a greater concentration than the concentration of binding agent within the mat or, for example, the concentration on the opposite face of the mat.

In ultimate formation, this continuous phase may be spiral or serpentine, but still there is no uniformity of binding agent throughout the ultimate product, and there are continuous areas of the ultimate product having a binding agent concentration above that which is necessary to achieve the optimum characteristics.

The problems which exist with the above described prior art techniques are not eliminated by the other prior art suggestion, namely, the provision of an ultimate product by simultaneously suction depositing binding fibers and natural fibers. Here again, to achieve any stability of the order which is necessary for cigarette filters, the suggestions of the prior art lead to the use of excess binding agent. Moreover, to use any satisfactory technique similar to that under consideration in this paragraph, we have found that there must be control of the bonding fiber utilized in relation to the base or natural fiber utilized, both with respect to length of the respective fibers, and with respect to the quantity thereof.

A primary structural characteristic of the product provided hereby is that the same, and all the constituent components thereof, possesses complete randomness in three curvilinear dimensions. More specifically, the product hereof has all constituent components therein randomly oriented both longitudinally and laterally, and is free of any excess concentration of binding agent, as well as any continuous phase of binding agent. The randomness in three curvilinear dimensions cannot be over-emphasized because this permits the uniformity of binding agent throughout the ultimate product, proper resiliency of the ultimate product, and even filtration with the ultimate product. Consistent with the randomness in three curvilinear dimensions, the fibers incorporated in the ultimate product provided hereby have a length which is substantially shorter than the minimum dimension of the ultimate product, and preferably have a length which is one-half or less the minimum dimension of the final product, the minimum dimension of the final product normally being the diameter of a finished rod or rod segment, or if not circular, the minimum dimension of a cross section through the final product.

In connection with the exposed surface area considerations discussed hereinabove, we have found that in order to provide a satisfactory natural fiber filter element, it is necessary to more or less tack weld the fibers 'by a binding material such that the exposed surface area of substantially any fiber within the ultimate filter unit is substantially large when compared with the bound surface area thereof. In other words, we have found that while haphazard mixing, spraying, or emulsion coating techniques have previously been suggested, these techniques do not lead to the provision of a satisfactory natural fiber filter because the desired characteristics, as discussed, can only be obtained if the filter is so designed that the exposed surface area of the natural fiber is comparatively large with respect to the bonded surface area thereof. This consideration is additive with the consideration of randomness in three curvilinear dimensions.

The invention lies in the combinations of characteristics possessed by an ultimate product constructed in accordance herewith, and will 'be better understood after reading the following detailed description of the invention. Such description refers, in part, to the annexed drawings, wherein:

FIGURE 1 is a schematic flow diagram presenting the manner in which a product is preferably formed in accordance herewith;

FIGURE 2 is a sectional view i-llustratively presenting a cross-section of a product constructed in accordance herewith;

FIGURE 3 is a longitudinal sectional view of a conventional cigarette filter as in use today;

FIGURE 4 is a transverse partial sectional view of a cigarette filter such as shown in FIGURE 3; and

FIGURE 5 is a sectional view illustrating a crosssection of a modified product constructed in accordance with the instant invention.

In clarification of portions of the preceding discussion regarding randomness of orientation and uniform heterogen'iety in different directions, attention is first directed to FIGURES 2 through 4 of the drawings. A conventional cigarette filter such as in wide-spread use today can schematically be represented as shown in FIGURES 3 and 4. The fibers 18 within such a filter are predominantly longitudinally oriented, although there are crimps and bends in such fibers, and minor segments extending therefrom. The ends of a filter such as shown in FIG- U'RE 3 appears as shown in FIGURE 4 wherein the ends of such fibers 18 are exposed. In contrast with such an arrangement, FIGURE 2 presents a cross-section of a filter constructed in accordance herewith. This cross section is representative of that taken either longitudinally or laterally of the product of the invention. By referring to FIGURE 2, it will be noted that the fibers 1'7, l7, l7" and 17" are all randomly oriented in various diflering directions. These fibers, as shown, are bonded together by a suitable binding agent which is the illustrative embodiment of FIGURE 2 takes the form of an at least partially cured powder. The powder is designated by the black dots numbered 19.

As indicated above, the present invention is primarily concerned with the provision of an improved filter construction comprising predominantly natural fibers. It has been found that particularly suitable fibers for use in accordance herewith include kraft pulp fibers, sulphite pulp fibers, alpha pulp fibers in general, suitably shredded bagasse fibers, and cotton linters. These fibers may be bleached or unbleached, and moreover, as explained in more detail below, can be mixed with other types of fibers in accordance herewith.

In order to obtain a stable ultimate product as also indicated above, a suitable binding agent is incorporated in a filter constructed in accordance herewith. We have found that thermoplastic binding agents provide the most satisfactory result, but that other binding agents may be utilized. Polyethylene, polyesters, regenerated cellulose, cellulose esters, cellulose ethers, and thermo-sensitive adhesives of natural origin such as for example gum and carbohydrates, can be used. Moreover, as indicated more fully below, the binding agent may be either in fiber form, or in powder form. Notwithstanding the various considerations in this paragraph, polyethylene has been found to be entirely satisfactory, and is used in accordance with the preferred embodiment hereof.

Related to the foregoing, and as described more particularly below, we have found further that in order to provide a natural fiber filter element with satisfactory characteristics, the binding material must be incorporated in or mixed With, the base fibers when the binding agent or element is in a dry state, and in the process of transport, either in the form of a powder, or in the form of fine filaments. It is only with this technique that a tack weld can be achieved, and further, it is only with this technique that the structural properties of the natural fiber filters wherein the exposed surface area of the base fibers is substantial, can be achieved. Other forms, e.g., wet sheeting, drastically reduce the exposed fiber surface.

The tack welding which is achieved in the product hereof, is particularly important because this permits or yields an ultimate product free of binder layers or continuous phases of binding material, and accordingly, a product presenting uniform obstruction throughout to gas flow therethrough.

While the length of the individual fibers incorporated in their ultimate filter element constructed in accordance herewith may vary, we have found additionally that the most satisfactory elements can be formed where the ratio of the length of the fibers to the smallest dimension of the final product is between 0.5 and 0.05. In different terms,

the ultimate product has a thickness which is preferably greater than twice the length of the individual fibers in corporated therein, and for most satisfactory results in smoke filtration, such thickness corresponds to the length of at least 20 fibers.

The size of the particular binding or binding particle may vary from filter to filter, but to obtain the desired results with a dry powder type binding element, more than 50 percent of the same should have a particle size of 50 microns or less, and preferably a particle size of between 1.0 and 30 microns. If binding filaments are used, as opposed to a binding powder, then the same should have a length preferably shorter than the length of the natural fibers included within the product.

In order to make filter elements from natural fibers, it has previously been suggested that fiber suction depositing techniques be employed. Thus, in British Patent 757,841, and in possibly more pertinent United States Patent 2,992,- 154, there are teachings of, for example, using a hammermill to disintegrate natural fibers, and of then using an air dispersion uction depositing technique for accumulation in a heterogeneous manner of the disintegrated fibers on a conveying screen. Still further, such patents suggest the subsequent transfer of the fibers by suitable conveyors, in conventional manner, to other conveyors, and then feeding of the fibers to forming and curing means. In accordance with these prior suggestions, the binding material is added into the air dispersion of the disintegrated fibers, and/ or is deposited simultaneously with the accumulation thereof on the suction depositing and accumulating conveyor. Alternatively, the prior art suggests spraying techniques and emulsion techniques, but as explained above, We have found that the utilization of a dry-type binding material is essential to achieving satisfactory results.

Still further, as indicated above, we have found that the exposed surface area of the individual fibers must be maintained substantial in comparison to the bound surface area thereof, and that a tack welding of the fibers by the binder is necessary.

We have further found that one suitable way of obtaining the results in question, and the structural properties with which the invention is concerned, lies in adding the binding material, Whether in the form of a dry powder or in the form of filaments, to the fibers at the time of disintegration thereof in a suitable device, such as, for example, a hammermill. In other words, to yield the structural properties which are essential to this invention, we have found that one suitable technique is to introduce binding material, and/or mix the same with the fibers during the grinding of the fibers, as opposed to subsequently thereto. In this manner, it appears that more than a mere mixing of the base fibers with the binding agent is obtained, and the ultimate result of a substantially large exposed surface area of the individual fibers and the tack welding thereof can be obtained during the curing operatious.

The intimate mixture of the base fibers and the binding agent, whether in powder form, or in filament form, as opposed to the random mixture obtained with prior art techniques readily permits, during a curing operation of suitable type, the tacking of the base fibers to one another, without distributing the binding material over any substantial surface area of the base fibers themselves.

The general process referred to above is illustratively presented in FIGURE 1 wherein it will be noted that the boxes 1 and 2 designate respectively pulp and binder storage areas. The pulp is tranfserred from the storage area by a suitable transfer means 3, and is transferred to the hammermill 9 by a suitable conveyor '7. Similarly, the binder is transferred from its storage .area 2 by means of a suitable transfer apparatus 6 through a feed control station 8. The station 8 governs the feed of a binder therefrom and to the hammermill station 9. At the hammermill station, there is a disassociation of the fibers and binder and intimate mixing thereof so as to form a homogeneous mass which is dispersed onto a conveying apparatus It From the conveying apparatus N, the deposited mat or mass is fed through a collector 11, and then by means of a transfer apparatus 12, fed through a processing station 13. At the processing station 13, the mass is heated so as to make the binder adhesive and there is a gathering of the mass into the desired ultimate formation. From the processing station, the formed mass is cooled, then cut, then transported.

The present invention lies in the structural characteristics of the ultimate filter which yield the intended results, and the foregoing suggestion as to the technique which can be employed to achieve the structural properties constitutes merely an explanation of what we have found to be a satisfactory mode of producing the structural properties. The particular suction depositing apparatus, harnmermill type unit, curing operation, and the like can be varied, and since there are various conventional previous suggestions as to the manner in which these steps can be carried out, further discussion thereof appears unnecessary.

PREFERRED STRUCTURAL PROPERITES OF CIGARETTE FILTER The invention has been discussed generally hereinabove as applicable in the formation of any filter element, regardless of its intended use. The basic aspects of the invention, are thus adequately set forth in the preceding description, but since the invention finds particular utility in the formation and construction of cigarette filters, the structural properties possessed by the same in accordance herewith are of some importance.

For a cigarette filter in particular, we have found that the ultimate product has a hardness, and a so-called resistance to draw in an optimum range for cirgarette filters.

The apparent density of an ultimate cigarette filter constructed in accordance herewith should be between 4 and 8 gms. per meter of conventional cigarette diameter. Apparent density means weight per unit volume. The term apparent is used because a filter body constructed in accordance with the invention necessarily has some air voids therein. A conventional cigarette filter has a radius of .4 cm., and accordingly has an area of .503 cm. The length of such a filter is 9.0 cm. Accordingly, the volume is 4.5 cc. Thus, the term apparent density means that the cigarette filter Weighs between 4 and 8 gins/meter, or that a conventional size cigarette filter weighs between .4 and .8 gms.

Regardless of the particular type of fibers used, the same preferably have a density of between 1.46 and 1.60. Fibers having such density have proved to possess the desirable sorbent characteristics for a filter element, and the desired hygroscopicity.

The density of the particular binding agent, like the density of the fibers, can vary in accordance with the invention. The particle size and density of the binder vary together, however, and it has been found that a preferred particle size is between .2 and 50 microns, when the density of the binder is between .90 and .95. From this description, it should be apparent that a dry powder binding agent is preferred.

Hygroscopicity or the affinity to retain moisture aerosol is also a property which must be possessed by smoke filters. We have found that the hygroscopicity of filter elements having the structural properties of the instant invention are greatly improved and may be controlled by selection of appropriate fiber-binder combinations.

With respect to the ratio of binding agent to base fiber on a weight basis, and for cigarette filters, we have found that a ratio of between :1 and 3:1 (base fiber to binder on a weight basis) is satisfactory. On a volume basis, the ratio would be between 1:1 and 1 :3.

Example 1 As a specific example, where the base fibers comprise alpha pulp, and dry powder polyethylene is used as a binder, a cigarette filter element can be formed in accordance herewith by utilizing 165 gins. of polyethylene and 495 gms. of alpha pulp as the mixture fed to the hammermill. The polyethylene has a particle size of 50 microns. The ultimate filter then contains essentially 25 percent binder. The product is made in accordance with the process described above.

Although in the above example a 25 percent binder is incorporated in the ultimate product, and although this has proved satisfactory, we have found that the limits can be varied, but that for the development of desirable filter and structural properties, a fiber range of 70 percent to percent, and a binder range of 15 percent to 30 percent are definitely preferred.

MODIFICATIONS Having now described the basic aspects of a filter product formed in accordance herewith, and the structural properties possessed by a cigarette filter element formed in accordance herewith, it will be apparent that certain modifications can be made to the described embodiments without departing from the scope and spirit of the invention. Within these modifications is the use of a mixture, for example, of alpha pulp fibers with synthetic fibers equaling up to /3 the ultimate final fiber composition. Such a mixture can serve as a base fiber within the terminology used above. In any instance where a mixture of base fibers is used, and there is a variation in densities, then the densities referred to hereinabove will be the average densities of the mixture. Thus, even where the mixtures are used, the structural properties hereinabove prescribed are applicable.

Further, although the preferred filter consists only of the base fibers and the bonding agent, it is contemplated within the scope of the instant invention to include therewith a minor proportion of one or more additives in order to realize certain specific properties or characteristics in the final product. For example, various sorbent particles may be included to improve the filtration effected by the filter structure. Exemplary of such materials are activated carbon, silica gel, alkali metal aluminosilicates, such as Molecular Sieves sold by Linde Company, a division of Union Carbide Corporation, sucrose, activated alumina, volcanic ash, granular calcium carbonate, granular sodium carbonate, fullers earth, magnesium silicates, asbestos powder, metallic oxides such as iron oxide and aluminum oxide, metal treated carbon and the like. Additionally, where porosity or strength properties are of major consideration, then metal fibers or even fiberous carbon can be included. Moreover, taste modifiers such as menthol or other similar materials may be incorporated for obvious purposes. Mixtures of the above materials are also contemplated, although it is important to recognize that while the additives and/ or fillers listed above can be used if a particular effect is desired, they must be maintained in minor proportion in the overall filter in order to insure the uniformity which is one of the basic characteristics of this filter structure. From a practical standpoint, the quantity of additive should not exceed approximately 30 percent by volume of the filter body. Substantially uniform dispersal of the additives, which preferably have a particle size below 10 mesh, can be effected by introducing the same into the hammermill 9 with the pulp and binder wherein a homogeneous mass is formed by intimate mixing of the constituents. On gathering and heating of the mass in the processing station 13, the bonding agent binds the same together to form a stable structure, which, after cooling, may be cut and transported for further use.

FIGURE 5 illustrates a modification of the basic filter of this invention wherein parts similar to the embodiment of FIGURE 2 are designated by the same reference numerals. In this embodiment an additive or additives 9 20 such as those identified above is substantially uniformly dispersed in the filter body and the binding agent 18 randomly bonds the fibers 17, 17, 17", 17, and the additive 20 together.

CONCLUSION In the preceding description, the term curing has been used to indicate a heating step. In essence, during the processing step 13 of FIGURE 1, we have found that it is desirable to precure the binder or preheat the same whereby it becomes tacky, and to thereafter finally cure the same, if necessary. Tacking of the fibers to each other, as opposed to coating the same for purposes of achieving dimensional stability, is the ultimate result desired. Accordingly, the curing operation should be such that it does not result in a spreading or overall coating. Grinding of the binding agent with the base fibers, in the manner explained, tends to prevent any spreading during the curing operation.

While no mention has been made hereinabove of the diameter of the fibers used as base fibers or as binding fibers in accordance herewith, it will be appreciated that the diameter or cross-sectional dimension of any of the fibers is only a small minor fractional part of the length thereof. Thus, this comparison of dimensions set forth in this paragraph is utilized for definitive purposes, and should be sutficient.

Notwithstanding the fact that hardness, resistance to draw, and like terms have been used hereinabove without reference to specific test procedures, it will be understood by those of ordinary skill in the art that the values given are those which result from standard hardness test procedures, standard resistance to draw procedures and other standard test procedures for determining the specific characteristics in question.

After reading the preceding detailed description of illustrative and preferred embodiments of the instant invention, it will be apparent that the objects set forth at the outset of the present specification have been successively achieved.

Accordingly, what is claimed is:

1. A tobacco smoke filter body or the like consisting essentially of a multitude of fibers randomly disposed in said filter body and free of any substantial directional orientation within said body, said fibers having a length substantially shorter than the minimum dimension of said filter body, and a bonding agent within said body randomly bonding said fibers together, said bonding agent being at least substantially uniformly dispersed within said filter body, said bonding agent joining said fibers at spaced locations and covering only a minor portion of the surface of the individual fibers, said bonding agent being free of any substantial directional orientation within said body.

2. A filter body as defined in claim 1 wherein said fibers are at least predominantly natural fibers and wherein said bonding agent is a synthetic material.

3. A filter body as defined in claim 1. wherein said fibers are natural fibers and wherein said bonding agent comprises a multitude of at least partially cured synthetic resin particles.

4. A filter body as defined in claim 1 wherein said fibers are natural fibers and said bonding agent comprises a multitude of synthetic fibers, said synthetic fibers being shorter than said natural fibers.

5. A filter body as defined in claim 1 wherein said fibers are at least predominantly natural fibers, wherein the ratio of the length of said fibers to the smallest dimension of said body is between 0.5 and 0.05, and wherein said bonding agent comprises a multitude of synthetic resin particles more than 50 percent having a particle size no greater than 50 microns.

6. A filter body as defined in claim 1 and formed as a cigarette filter having an apparent density of between 4 and 8 gms./ meter.

7. A cigarette filter consisting essentially of a body of randomly disposed fibers, at least the major portion of said fibers being natural, said fibers being at least substantially uniformly bonded in any cross-section of said filter by a resin at least substantially uniformly dispersed within said filter and comprising a minor portion by volume of said filter, said fibers being present in an amount of between 70 and percent by weight, and said resin being present in an amount of between 340 and 15 percent by weight, said fibers having a length substantially shorter than the minimum dimension of said filter, said fibers being free of any directional orientation within said filter, said resin joining said fibers at spaced locations and covering only a minor portion of the surface of the individual fibers, said resin being free of any substantial directional orientation within said body.

8. A tobacco smoke filter body or the like consisting essentially of a multitude of predominantly natural fibers randomly disposed in said filter body free of any directional orientation therein, said fibers having a length which does not exceed one-half the minimum dimension of said body, and a binding agent within said body fixing said fibers in permanent relative positions, said binding agent comprising a multitude of discrete binding elements smaller than said fibers, said elements being at least substantially uniformly dispersed within said filter body, said elements joining said fibers at spaced locations and covering only a minor portion of the surface of the individual fibers, said elements being free of any substantial directional orientation within said body.

9. A filter body as defined in claim 8 wherein said natural fibers are selected from the group consisting of kraft pulp fibers, sulphite pulp fibers, alpha pulp fibers, shredded bagasse fibers, cotton linters, and mixtures thereof, and wherein said binding agent is selected from the group consisting of polyethylene, polyesters, regenerated cellulose, cellulose esters, cellulose ethers, natural thermosensitive adhesives, and mixtures thereof.

It). A filter body as defined in claim 8 wherein said natural fibers are alpha pulp fibers and said binding agent is polyethylene.

11. A filter body as defined in claim 8 wherein said binding elements are binding particles having a particle size of between .2 and 50 microns and a density of between .91 and .95.

12. A tobacco smoke filter body or the like consisting essentially of a multitude of fibers randomly disposed of said filter body and free of any substantial directional orientation within said body, said fibers having a length substantially shorter than the minimum dimension of said filter body, and a binding agent within said body randomly binding said fibers together, said binding agent being at least substantially uniformly dispersed within said filter body, said filter body being free of any substantial directional orientation of said binding agent within said body, said fibers having a density of between 1.46 and 1.60 gms./cm. and a length which is less than one-half and greater than one-twentieth the smallest dimension of said filter body, said binding agent joining said fibers at spaced locations and covering only a minor portion of the surface of the individual fibers, said binding agent being free of any substantial directional orientation within said body.

13. A filter body as defined in claim 12 wherein the ratio of the weight of said binding agent in said body is between 5:1 and 3: 1.

14. A tobacco smoke filter body or the like consisting essentially of a multitude of fibers randomly disposed in said filter body and free of any substantial directional orientation within said body, said fibers having a length substantially shorter than the minimum dimension of said filter body, an additive comprising a minor part of said filter body substantially uniformly dispersed in said filter body, and a bonding agent within said filter body randomly bonding said fibers and said additive together, said 11 bonding agent being at least substantially uniformly dispersed within said filter body, said bonding agent joining said fibers at spaced locations and covering only a minor portion of the surface of the individual fibers, said bonding agent being free of any substantial directional orientation within said filter body.

15. A filter body as defined in claim 14 wherein said additive comprises a maximum of 30 percent by volume of said filter body.

16. A filter body as defined in claim 14 wherein said additive is selected from the group consisting of activated carbon, silica gel, alkali metal aluminosilicates, sucrose, activated alumina, volcanic ash, granular calcium carbonate, granular sodium carbonate, fullers earth, magnesium silicates, asbestos powder, metallic oxides, metal treated carbon, fibrous carbon, metal fibers, menthol and combinations of the same.

References Cited by the Examiner UNITED STATES PATENTS 2,881,770 4/1959 Tovey 13l208 3,025,861 3/1962 Cobb 131-208 3,034,947 5/1962 Conlisk et al 131 208 3,03 9,908 6/ 1962 Parmele 131-208 FOREIGN PATENTS 757,841 9/1956 Great Britain.

SAMUEL KOREN, Primary Examiner.

5 MELVIN D. REIN, Examiner.

Claims (1)

1. A TOBACCO SMOKE FILTER BODY OR THE LIKE CONSISTING ESSENTIALLY OF A MULTITUDE OF FIBERS RANDOMLY DISPOSED IN SAID FILTER BODY AND FREE OF ANY SUBSTANTIAL DIRECTIONAL ORIENTATION WITHIN SAID BODY, SAID FIBERS HAVING A LENGTH SUBSTANTIALLY SHORTER THAN THE MINIMUM DIMENSION OF SAID FILTER BODY, AND A BONDING AGENT WITHIN SAID BODY RANDOMLY BONDING SAID FIBERS TOGETHER, SAID BONDING AGENT BEING AT LEAST SUBSTANTIALLY UNIFORMLY DISPERSED WITHIN SAID FILTER BODY, SAID BONDING AGENT JOINING SAID FIBERS AT SPACED LOCATIONS AND COVERING ONLY A MINOR PORTION OF THE SURFACE OF THE INDIVIDUAL FIBERS, SAID BONDING AGENT BEING FREE OF ANY SUBSTANTIAL DIRECTIONAL ORIENTATION WITHIN SAID BODY.

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