US3543769A

US3543769A - Cigarette filter plug

Info

Publication number: US3543769A
Application number: US693656A
Authority: US
Inventors: James B Arthur; John J Osmar
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1967-12-26
Filing date: 1967-12-26
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01

Description

I United States Patent 113,543J69 [72] Inventors James B. Arthur; 3,253,969 5/1966 Pannill, Jr., et a1. 13 l/267X John J. Osmar, Charlotte, North Carolina 2,966,157 12/1960 Touey et al. 131/269 [2]] Appl. No. 693,656 3,093,142 6/1963 Swerdloffet al.. 131/268X [22] Filed Dec. 26,1967 3,131,428 5/1964 Mika l31/268UX Continuation f 50 3,224,453 12/1965 Mahoney et al. 131/268 N 14 r956 abandoned, which 3,396,073 8/1968 Touey et al. 131/761UX is a division of Ser. No. 265,518, p i Examiner Melvin Rein 15, 1963' abandoned- Attorneys-Leonard Horn, S. D. Murphy and William J. [45] Patented Dec. 1, 1970 Mason [73] Assignee Celanese Corporation a corporation of Delaware [54] CIGARETTE FILTER PLUG 4 Claims Drawing Flgs' ABSTRACT: A cigarette filter plug is described which is com- US. Cl. posed of a plurality of dereglstered crlmped cellulose ester l 1 Int. Cl. filaments the filaments extending approximately longltn- 01/04 A24f13/06 dinally from end to end of the plug and the plug having of Search preferably to independent filaments having 105, 261-269 about 4 to 40-crimps per inch. The relationship between linear er filament and ercent of fiber in the filter lu falls within [56] References Cited she zone CDGl-l sf FIG, 1. The cellulose esteffiliments in the UNITED STATES PATENTS plug are unbonded and the plug is characterized by good firm- 3,079,978 3/1963 Cobb, Jr'., et al l3 l/267X ness and resilience.

PERCENT FIBER DENIER PER FILAMENT Sheet of 2 lb 2 l4 DENIER PER FILAMENT James B. Ar/hur John J. Osmar Sheet of 2 C: T n 26 Q James 5. 'Ar/hur JOh/i J. 05mm CIGARETTE FILTER PLUG This application is a continuation application of application Ser. No. 604,506 filed Nov. 14, 1966, now abandoned which in turn is a divisional application of application Ser. No. 265,518 filed Mar. 15, 1963 now abandoned.

The present invention relatesto novel filters and more particularly novel cigarette filter plugs.

In the filtration of smoke produced by combustion of tobacco it has been proposed to employ crepe paper, absorbent cotton, etc. In the last decade the overwhelming proportion of commercially available cigarette filters have comprised longitudinally extending crimped filaments bonded to one another at their contact points by solvation bonds. The procedure for producing such filters involved producing a tow or untwisted bundle of several thousand continuous filaments, crimping the tow, opening the tow to deregister adjacent crimps, fluffing the opened tow to pennit subsequent uniform X application of a plasticizer, pulling the tow through the zones of plasticizer application and fluffing, wrapping the plasticized tow in paper, severing the wrapped tow into rods of predetermined length and thereafter curing the rods to effect bonding between adjacent filaments at their contact points.

Another object of the invention is to produce novel cigarette filter plugs.

Other objects and advantages of the invention will become apparent from the following detailed description and claims taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a graph identifying the novel plugs embraced by the present invention;

FIG. 2 is a schematic view of one apparatus for making plugs in accordance with the present invention; and

FIG. 3 is a schematic view of an alternative apparatus for making plugs in accordance with the invention.-

In accordance with the method of making the disclosed plugs of the present invention, with selected tows when the opening of the tow is effected with certain equipment the resulting deregistered tow can be formed into filters without the need for plasticization and subsequent curing. It is even possible to eliminate the fluffing step since there is no need to prepare the tow for uniform receipt of plasticizer; without plasticizer-applying or fluffing-apparatus the need for equipment to pull it therethrough is also overcome. Thus, in its simplest form of rod making equipment comprises only tow crimp-deregistry equipment followed immediately by wrapping equipment.

The opening equipment must be such that there is substantially complete deregistry between the crimps of adjacent filaments. Lesser deregistry results in plugs which are too soft, difficult to wrap initially in forming the rods as well as in joining the rods to tubes of tobacco in making filter tip cigarettes, and which do not spring back after compression (as between the fingers or lips during smoking) with attendant channeling of the smoke. For these same reasons the opening equipment should not operate so strongly on the tow that the crimps are pulled out and the tow is of diminished bulk; while this could be compensated for by utilizing heavier tows the resultant plugs would be so dense as to make it exceedingly uncom-' fortable to draw smoke through the filter, i.e. its pressure drop would be too high.

One apparatus especially suited for effecting such deregistry comprises at least one pair of cooperating surfaces.

Advantageously the surfaces are rolls adapted to rotate either by a positive drive or idly by contact with a rotating roll. Advantageously one roll of each set is rigid while the other has a yielding surface, e.g. steel versus rubber or synthetic elastomer and the rolls are urged into contact so that both rotate upon driving of but one. At least one roll of one set is not smooth surfaced so that all filaments across the width of a tow passed therebetween will not be identically treated.

In one embodiment, there are provided two pairs of rolls with their nips in horizontal or preferably vertical alinement. One roll of each pair is driven and has a smooth rubber surface. The other surface of each pair is idly mounted and spring urged into contact with its driven mate to be caused to rotate thereby. The idle roll has a helical thread cut in its steel surface. Advantageously the downstream driven roll is driven at a surface speed faster than that of the upstream driven roll. Thereby the tow is subjected, while being fed along a predetermined path, to a differential gripping action between a plurality of points spaced from one another both longitudinally and transversely of the path, so that certain laterally spaced sections of the tow are positively gripped relative to other laterally spaced sections of the tow, alternating with the said gripped sections, which are not gripped at all or are gripped at different relative points. In this manner, there is produced, as a function of thedifferential positive gripping of the tow, a relative shifting of adjacent filaments longitudinally of the tow, whereby the crimps are moved out of registry with oneanother. Preferably, although not necessarily, the differential gripping action is such that a relative longitudinal displacement between adjacent filaments of the tow is also effected, so that the combination of two transverse filament movements brings about the complete opening of the tow.

By way of definition, the term gripping gripping"(or any variant thereof) is used herein to denote the confinement of the tow by two opposed members which tightly engage the tow at its opposite faces, and the term differential gripping is used to denote the confinement of the tow between two opposed members, as well as between sets of such opposed members, which have zones in which the tow is tightly engaged by the members alternating with zones in which the tow is only loosely or not engaged by the said members. The terms include a mere one-sided frictional sliding engagement between the tow and a member past which the tow moves.

The nonsmooth surface has been described as preferably helical, this being one of the easiest surfaces to produce and one of the most satisfactory to work with. Advantageously there are about 10 to 20 threads per inch and the ridges which contact the smooth surfaces are flattened. Each grooved roll may be helically grooved in opposite directions from its center to its ends, or may be continuously helically grooved in either direction across the roll. Where several helical rolls contact the tow in sequence the arrangement of grooves can be alike on successive rolls or in opposite directions on successive rolls or grooved from the center to the end of opposite directions on successive rolls.

While helical threads are preferred the surfaces of the nonsmooth rolls may be formed of circular or cylindrical ridges or of elliptical or undulating rings. It can even comprise a checkerboard of alternated raised and lowered surfaces, or it can comprise spaced projections for pinching the tow against the cooperating surface.

It has been found useful to employ two sets of rolls whose nips are about 10 to 50 inches and preferably about 15 to 25 inches apart. While the tow path in moving between rolls sets may be inclined as much as 45 to the vertical, advantageously its inclination is less than about 25 and preferably it is substantially vertical. The profiled or nonsmooth roll of each pair is advantageously urged against the smooth roll with a force of about 5 to 30 or more and preferably about 5 to 15 pounds per linear inch of contact between the rolls. Lower forces may result in excessive slippage where the tow is not extremely heavy, and higher forces may result in injury to the roll surfaces and to tow passing therebetween.

The first or rear driven roll pulls the tow along from a bale or ball warp over bars which straighten it out slightly and control the sidewise motion. The surface speed of the rear driven roll generally ranges from about 50 to percent of the speed at which the the opened tow is ultimately received by the garniture and fed to the belt of a cigarette wrapping machine by which it is formed into filter tips; preferably the speed is about 75 to 100 percent of the belt speed, i.e. the tow 'in the filter tips is substantially as long as in the crimped unopened state. The front, second or downstream" driven roll operates at a speed varyingfrom about I20 to 300 percent and preferably from about to 225 percent of .the upstream product uniformity special apparatus is provided for handling the tow between the grooved rolls and the bale in which it is shipped. Because of the tight compression within the bale the tow band width will vary as well as the weight per unit length and the ease of withdrawal from the bale. Further variations result as the tow position changes vertically and laterally within the bale. As the bale is used up, there is a change in the length of tow from the top of the bale to the overhead guides normally used; this change in length effects a change in tension and thus in weight per unit length. Such variations are overcome by introducing a small amount of pretensioning upstream of the grooved rolls. Specifically, the tow from the bale is withdrawn upwardly and caused to pass over a substantially straight guide surface which causes it to be flattened. The guide surface, which is preferably a horizontal rod positioned about 4 feet over the bale, allows shifting of. the tow band laterally therealong as the tow is withdrawn first from one side of the bale and then from the other side. As a consequence jerking and plucking of the band are eliminated. The lightly tensioned tow is now of substantially constant width and weight per unit length and passes horizontally through an air spreader in which its width is increased several fold. The wide band may be passed over several additional direction-changing guide bars before reaching the grooved rolls. While these bars do not affect any deregistry or opening, they do serve to pretension the band uniformly so that it will be in the best condition for being operated upon by the grooved rolls. 7

Even with this equipment, however, only a fraction of the tows commercially available will produce satisfactory filter plugs in the absence of plasticizer. The tow is preferably composed of a plurality of crimped continuous filaments of an organic derivative of cellulose, e.g. esters or ethers of cellulose such as cellulose acetate, cellulose propionate and'cellulose acetate propionate, highly esterified cellulose containing less than 0.29 free hydroxyl groups per anhydroglucose unit such as cellulose triacetate, and the like. Other filamentary materials such as rayon (regenerated cellulose) lineary superpolyamides such as nylon-6 and nylon-66, linear polyesters, and

polymers and copolymers of vinylidene compounds such as number ofcrimps per inch in the tow can range up to about 30- 40, but preferably averages between about 4 and 25, e.g. 8 to l2 computed on an inch of straightened tow. The percent tensioned length-contracted length contracted length X 100 crimp, i.e.

ranges from about 50 to 200 percent and preferably from about 75 to 150 percent.

In addition to meeting the foregoing requirements, the denier per filament should bear a particular relationship to the proportion of the plug or filter rod apparent volume which is actually air space rather than being occupied by fiber. This relationship is illustrated graphically in FIG. l of the drawing which was arrived at from date obtained with secondary cellulose acetate tows formed into filter rods of 17 mm. length and 25 mm. circumference, the individual filaments being Y- shaped in cross section. The topmost limit of the chart represents aplug of solid acetate, i.e. 100 percent fiber, while the lowermost limit represents no acetate or 0 percent fiber. The zone A,C,D,E,F,G,H encloses those plugs falling within the present invention. Above this zone even at low percentages of fiber the pressure drop, i.e. force required to draw smoke therethrough at the rate of U5 cc. per second, will be unduly high, e.g. in excess of about 90 mm. of water. Below this zone filter plugs will be so soft that often there will be wrinkles and dimples in the encircling paper. Moreover, there may be so little resistance that wrapping may be rendered difficult. To the right of the zone the individual filament denier is so great that there is relatively little filament surface available for filtration, the filaments are relatively coarse and the overall effect if little more than an empty tube. To the left of the zone the rods are quite soft even when they contain enough fiber to give effective filtration.

The whole enclosed zone is not equally advantageous. The area CDGl-l represents the preferred rods and the area HKLM the most preferred rods, from the standpoints of performance, ease of production, firmness, and resilience. The combination of firmness with resilience is most important in unbonded plugs. In actual use filters are compressed and distorted out of shape. While the paper wrapper may rebound, often the filaments do not so that .channels are formed between the paper and the periphery of the filaments making up the plug. Moreover, pressure on a bonded filters causes only the peripheral filaments near the point of pressure application to be displaced so that smoke channels preferentially through the remainder of the filter; with the novel plugs, the pressure is transmitted so that many filaments adjust their positions and all are effective in filtration. Consequently, with bonded plugs the theoretical smoke removal efficiencies determined in the laboratory ,will frequently not be realized in practice due to the smokes bypassing the filter. When the filaments are independent, i.e. unbonded, they are free to bounce back, being unrestrained by adhesive bonds. Consequently the performance of the most preferred unbonded plugs of the present invention approach the theoretical values of laboratory tests. This is further evidenced by carefully longitudinally slitting the paper wrappers of bonded and unbonded plugs. The wrapper ofthe unbonded plugs flies open under. the force of the filament and the cross-sectional area of the filament bundle increases by at least about 20 percent and often more than 35 percent. With bonded plugs, the severed paper edges open only slightly and the cross-sectional area of the filament bundle is substantially unchanged.

Another way of establishing this is by testing the plugs for compressibility. Compressibility, the inverse of firmness, is measured by permitting a weighted knife edge to rest transversely of the plug for 10 seconds; the extent to which the plug returns to its original diameter is an index of firmness. After removing a -knife edge loading of 4-ounces the preferred novel plugs return rapidly to a diameter of at least about percent and preferably at least about percent of their original diameters, both faster and higher than for corresponding plasticized plugs.

The preferred plugs usually exhibit a smoke removal efficiency of at least about 20 percent and preferably at least about 30 percent, determined as follows: 12 puffs of 35 cc., i.e. 2 seconds of puffing are drawn from a lit cigarette through the filter and through a trap having on its bottom a sintered glass disk. 2 grams of sifted alpha cellulose are placed on the disk, producing a pressure drop of about 5 centimeters of water. The trap is immersed halfway in a dry ice-acetone bath. The formula for the smoke removal efficiency is as follows: Percent efficiency Increase in Weight of Filter Increase in Weight of Filter Plus Trap The foregoing evaluations were made with Y cross section filaments, which exhibit a somewhat greater firmness and smoke removal efficiency than regular cross section filaments at any particular percent fiber in FIG. 1. The effect is that the lower boundaries of the enclosed zones of FIG. 1 will have to be raised somewhat for regular cross section fibers. Alternatively, the paper wrapper could be made more firm by being built up. Similarly, the upper limit could be raised somewhat by employing filter plugs less than 17 mm. long thereby to diminish the pressure drop. Other cross sections will give results approximately intermediate Y and regular. The curves were determined with secondary cellulose acetate having a specific gravity-of 1.3; different fibers will result in a small displacement of the curves although their shapes will be the same.

FIG. 2 shows a suitable apparatus for producing the novel plugs. In FIG. 2 the tow 1 1 is taken from a bale 12 passing over an overhead horizontal bar 13. The tow direction is thereby diverted to the horizontal, the tow entering air spreader 14 wherein its width is increased several fold. The tow 11 is pretensioned by direction'changing

bars

15, 16, 17 and 18 but the crimp is still visible with the crimps in registry between adjacent filaments across the tow band. The tow 11 next passes between helically grooved idle steel roll 19 and driven rubber roll 20 and then between similar steel and rubber rolls 21, 22, whereby opening is completed. The opened tow passes over pin 23 which ensures its removal from the rolls and the tow is taken up in the garniture trumpet 24 of a cigarette making machine 25 wherein it is wrapped in paper and discharged as a continuous plug 26 which is severed by a knife 27 into short plugs 28 of predetermined length.

FIG. 3 shows an alternate apparatus wherein the tow 11 leaving pin is passed about another pin 29 which directs it vertically downward between the nips of

rolls

19, and 21, 22 (now positioned for a vertical tow path). The opened tow now passes directly to garniture trumpet 24 even without an intermediate separator pin.

The invention will be described further in the following illustrative examples.

EXAMPLES 1T0 9 Secondary cellulose acetate tows having about 12 crimps per inch and 100 percent crimp are passed throughthe apparatus of FIG. 2 wherein the nip of

rolls

21, 22 is 20 inches from that of

rolls

19, 20, roll 22 operating at 1.7 times the speed of roll 20.

Rolls

19 and 21 are made of steel having cut therein a helical thread of 14 turns per inch, Each. turn has a 60 apex angle at its base and a flat 0.017 inch wide. Rolls 19 60 and 21 are urged against

rolls

20, 22 with a spring force of 10 pounds per linear inch of contact.

In the following runs the indicated results are achieved, the examples being indicated in FIG. 1:

Dcnler Total Cross Percent Pressure Percent Ex per Ill. denier section fiber drop, smoke X1, 000 mm. 1120 removal efficiency 6 EXAMPLES 10-55 Total denier X1,000

Denier per filament Zone 01 figure 1 Cross Percent section b Example er R= Regular. 1==H, K, L, M; 2 F, G.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of the invention.

We claim:

1. A cigarette filter plug having a pressure drop of less than about 90 millimeters of water and an acceptable smoke removal efficiency and firmness composed of a bundle of independently crimped cellulose ester filaments each extending approximately longitudinally from end to end of said plug, said filaments being free of interfilamentary bonding, the plot of denier per filament versus percent of fiber for said plug falling within the zone ACDEFGI-I of FIG. 1, said bundle being surrounded and compressed by a paper wrapper, the removal of which results in an increased in the cross-sectional area of said bundle by at least 20 percent. 7

2. A plug according to claim 1 wherein said filaments are comprised of cellulose acetate.

3. A plug according to claim 1 wherein at least some of said filaments are Y-shaped in cross section.

4. A cigarette filter having a pressure drop of less than 90 millimeters of water and an acceptable smoke removal efficiency and firmness composed o a bundle of about 5,000-

33,000 independent cellulose ester filaments having about 4-40 per inch with the crimps of adjacent filaments being out of registry, said filaments extending approximately longitudinally from end to end of said plug, said filaments being free of interfilamentary bonding, the plot of denier per filament versus percent fiber for said plug zone within the zone CDGl-I of FIG. 1, said bundle being surrounded and compressed by a paper wrapper, the compressibility of said plug being such that the diameter thereof will return to at least about percent of the original diameter after resting a knife edge transversely on said plug for 10 seconds under a load of 4 ounces.

Patent No.

UNITED STATES PATENT OFFICE Dated December 1, 1970 n fl LJamqs B. Arthur and John J. Osmar It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1,

Column 2, "gripping".

Column 2,

Column 3,

Column 6,

line

73, "alinement" should read "alignment".

22, 'gripping" gripping" should read 30, "in-" should read "ex".

43 "of" should read "in".

46, "aerylonitrile" should read "acrylo- 3, "date" shoudid read "data".

21, "if" should read "is".

33, "filters" should read "filter".

58, "increased" should read "increase".

68, after"440" should be inserted crimp 72, after "zone" should be inserted "fall Signed and sealed this 11 th day of May 1971 (SEAL) Attest:

EDWARD M.FIETCHER,JR. Attesting Officer WILLIAM E. SCHUYLER, JR Commissioner of Patents