US3413698A - Filter tow treatment - Google Patents

Description

Dec. 3, 1968 T. c. FRITZ ET AL 3,413,698

FILTER TOW TREATMENT Filed Dec. 29, 1965 4 Sheets-Sheet 1 THEOD ORE 6. FR! TZ R/CHA RD E D YER INVENTORS A TTOR/VEYS Dec. 3, 1968 1'. c. FRITZ ETAL FILTER TOW TREATMENT 4 Sheets-Sheet 2 Filed Dec. 29, 1965 QQQ Qmm

THEODORE C. FRITZ RICHARD E OVER INVENTORS 7 BY 4l% gig/11 2 1 @zZZ/Qu ATTORNEYS Dec. 3, 1968 T. C. FRITZ ETAL FILTER TOW TREATMENT Filed Dec. 29, 1965 4 Sheets-Sheet 5 THEODORE C. FRITZ RICHARD E 0 YER INVENTORS' BY m% 44% A Tram/Er;

Dec. 3, 1968 'r. c. FRITZ ETAL 3,413,693

FILTER TOW TREATMENT Filed Dec. 29, 1965 4 Sheets-Sheet 4 THE DOORS C F I?! 72 RICHARD E OVER INVENTORS A TTORIVEYS United States Patent 3,413,698 FILTER TOW TREATMENT Theodore C. Fritz and Richard F. Dyer, Kingsport, Tenn,

assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey Continuation-impart of application Ser. No. 419,748,

Dec. 21, 1964. This application Dec. 29, 1965, Ser.

2 Claims. (Cl. 28-1) ABSTRACT OF THE DISCLOSURE An improved method and apparatus makes possible the production of tobacco smoke filters from continuous fine denier multifilarnent tow. The method includes banding, pretensioning and longitudinally displacing individual filaments of the tow with respect to each other prior to applying a plasticizer with a dual roll applicator arrangement, and thereafter subjecting the tow to a gas jet treatment thereby uniformly distributing the plasticizer on the tow.

This application is a continuation-in-part of copending application Ser. No. 419,748, filed Dec. 21, 1964 entitled Filter Tow Treatment.

The present invention relates to a method and apparatus for the manufacture of tobacco smoke filters wherein fine denier per filament tow is processed to produce filters which are more uniform in appearance and performance, require less tow weight per unit of pressure drop and less plasticizer per filter than tobacco smoke filters produced by conventional methods and apparatus.

In the manufacture of tobacco smoke filters from special tows made up of crimped filaments of cellulose acetate and related plasticizable polymeric materials it is customary to use various mechanical means for processing the filter tow. It is already widely practiced and well known in the cigarette industry as disclosed by Crawford and Stevens, US. Patent No. 2,794,480, for example, to mechanically treat the tow in a plurality of steps which involve the filament separation of the crimped tow, applying thereto a spray coating of plasticizer, followed by forming and compacting the tow into the desired filter shape. In more recent disclosures, such as that of our co-workers Caines et al. in US. Patent 3,099,594, gaseous jet treatment means have been employed to obtain filament separation of the filter tow after it has been treated with an application of a plasticizer. Still another process for manufacturing tobacco smoke filters was described in the copending application of Fritz, Ser. No. 259,852, filed Feb. 20, 1963, now Patent No. 3,255,506, showing a mechanical roll means for obtaining improved filter tow separation. Although the above-mentioned prior art processes satisfactorily fulfill the requirements of many filamentary filter manufacturing operations, especially those in which relatively large denier per filament materials can be employed, they are not capable of producing a high quality fine denier per filament tobacco smoke filter which satisfies the present day demands of the industry for a filter having high tar removal capability. Such a filter can be produced by use of fine denier per filament tow and having each filament completely and uniformly separate from each other filament except, of course, at those points where the filaments are bonded together by the plasticizer. Maximum tar removal efliciency is thus obtained by requiring the tobacco smoke stream to impinge on a maximum area of filamentary material. This increase in tar removal efficiency can be surprisingly accomplished by a filter having a minimum weight of material per filter element per unit of desired pressure drop.

3,413,698 Patented Dec. 3, 1968 It is often difficult, if not impossible, to use conventional prior art processes to obtain such complete and uniform separation of fine denier filaments. It is accurate to say that prior art processes have not been able to accomplish such an operation with the uniformity and consistency necessary to produce an acceptable filter of the type described above. In referring to fine denier per filament we have reference to tows which are generally composed of filaments of smaller than 3 denier per filament.

The use of such fine denier per filament tows, which have a relatively large number of filaments per given tow cross-section, also requires the solution of special problems to insure the uniform application of a plasticizer if the filters having the required degree of uniform hardness throughout the finished filter elements are to he obtained. Moreover, the emphasis on obtaining maximum tar rem-oval efiiciency with the minimum weight of material per filter element requires that each filament be separated from each other filament throughout the body of the filter, except at those points where they are bonded together, to insure that the tobacco smoke stream passing thereto can impinge on the maximum area of filamentary material. Sufiice it to say at this point that tobacco smoke filter elements produced by the prior known methods did not possess the degree of uniformity and tow separation necessary to give a more effective tobacco smoke filter for removing tar, as will be shown by the examples to follow.

We have discovered that the aforementioned difficulties have been substantially overcome by our invention of a specialized process and apparatus for manufacturing a high tar removal, uniform and relatively light-weight tobacco smoke filter. Production of such a filter is made possible by the use of a fine denier per filament plasticizable tow which is extensively manipulated to give complete separation of the filaments, followed by a uniformly distributed application of the plasticizer. Such a uniform filamentary structures does not cause the smoke stream to channelize in localized areas of the filter as the smoke passes therethrough and therefore provides the necessary structural network of filamentary material to give the maximum contacting surface for the smoke stream.

Another important feature of our process is that our specialized tobacco smoke filter is produced in such a standardized manner that the ultimate smoker of a filtered cigarette will obtain a consistently uniform taste from each particular brand of cigarette. Furthermore, we have found the means to produce such a filter with a minimum weight of material per filter relative to the desired pressure drop reading and a substantially lesser amount of plasticizer per filter than the filter presently being made by conventional methods.

Therefore, according to the present invention, we have discovered a process and apparatus for the satisfactory production of fine denier per filament tobacco smoke filters which satisfy the demands of the trade for a filter having high tar removal properties. In essence the invention involves the combination of mechanical, fluid, and liquid plasticizer treatment steps of a fine denier per filament tow and the apparatus for carrying out these steps to effect substantially complete uniform separation of the filaments and an effective and uniform distribution of plasticizer throughout the filamentary mass. The apparatus of our invention is particularly characterized by the fact that it provides means for conveniently and effectively applying a liquid plasticizer in a highly uniform manner to the already uniformly separated filaments of the tow thereby obtaining in the ultimate product adequate filter hardness with a minimum amount of plasticizer. Furthermore, the substantial current interest in the selective removal of certain components of tobacco smoke also makes it desirable that any improved process or apparatus be readily adaptable to the inclusion of a step in which particulate additive such as activated carbon, sodium bicarbonate, cellulose acetate fioc and other solid particulate materials having selective removal properties may be added to the tow as it is being processed prior to the step of filter element formation. Our process and apparatus lends itself especially well to a further modification of the invention in which solid particulate additives may be added to the tow desired.

The subject matter which is regarded as our invention is clearly pointed out and distinctly claimed in the coneluding portion of the specification. The invention, however, as to its organization and operation together with the further objects and advantages thereof will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic side elevation view of an apparatus for carrying out the process of the invention.

FIG. 2 is an elevation view of a twin plasticizer applicator assembly of our invention viewed from the plane designated by line 22 of FIGURE 1 and looking in the direction indicated by the arrows.

FIG. 3 is a side elevation view of an apparatus adapted for carrying that modification of our process in which an applicator for incorporating a particulate additive into the plasticizer treated tow is provided.

FIGS. 4, 5, 6 and 7 are illustrations of the filament distribution in portions of the tow treated according to the various prior art procedures.

FIG. 8 is an illustration of a filament distribution in a portion of the tow prepared by employing the process and apparatus of the invention and illustrating the high degree of filament separation and uniformity of the filament separation attainable by our invention.

Referring now to FIGURE 1 which is a diagrammatic overall view illustrating the manner in which tow is processed in accordance with our one embodiment of our invention, a continuous, fine denier per filament, e.g., 3 denier per filament or smaller, crimped, multifilament tow 46 is withdrawn upwardly from supply package or bale 48 through a spreading or banding jet 50 supplied with air through pipe 52, and thence over fixed guide 54 or alternately over a freely rotatable roll guide. Tow 40 then passes downwardly to a pretensioning apparatus generally indicated by 56 and thence between the nip of contacting pretension rolls 58 and 60 thereof. Bottom roll 58 is rotatably mounted by suitable bearing means in fixed bracket 62 which is attached to the main frame 64 of the apparatus. Top roll 60 is rotatably mounted in suitable hearings in a vertically movable bracket 66 which in turn is attached to fixed bracket 62 by a leaf spring hinge 70 or other suitable means.

Top roll 60 is loaded downwardly against bottom roll 58 by means of a pneumatic diaphragm plunger or a weighted plunger 72. Tow 46 passes from the nip of pretension rolls 58 and 60 forward to the nip of filament separating feed rolls 74 and 76 which are driven from a main drive shaft (not shown) supported on base 99 of a plug making machine (not shown). The tension in the tow 46 entering filament separating feed rolls 74 and 76 is determined by the algebraic sum of the drag forces imposed on the tow by the concurrent and countercurrent air flow in banding jet 50, the frictional drag force of the tow in passing over fixed guide 54 (or the frictional bearing drag of the guide if a roller guide is used) and the drag force generated by the frictional drag of the pretension rolls 58 and 60.

The frictional drag of the pretension rolls 58 and 60 may be adjusted by means of the force applied to top roll 60 by the pneumatic or static weight loading means 72. This pretension on the tow entering the filament separating feed rolls 74 and 76 should preferably be kept at the minimum sufiicient to remove secondary crimps or folds in the tow Without substantially straightenin out the primary or fine crimps in the individual filaments. This roll pair 74 and 76 is mounted in much the same way as roll pair 58 and 60, that is, bottom roll 74 is rotatably mounted in suitable bearings which in turn are Supported in machine framework 64 of machine 99 while roll 76 is freely rotatable in hearings in bracket 76A. Bottom roll 74 is positively driven by a connection (not shown) to the main drive of machine 99 and drives roll 76 by frictional contact therewith.

In accordance with the invention top roll 76 has a configured surface, e.g., a surface with a plurality of circumferential square-form cross-section grooves and lands. Alternatively these grooves and lands may be interrupted at intervals around the circumference of the roll. When top roll 76 is loaded pneumatically by means of air diaphragm 78 it is pressed against bottom roll 74 which preferably has a resilient, smooth surface constructed, for example, of rubber with a hardness of about -80 as measured by the Shore A Durometer.

Portions of tow which are passed between the nip of the lands on top roll 76 and the smooth surface of bottom roll 74 are pullled against the tension generated by roll pair 58 and and are also displaced forwardly by a small increment relative to adjacent other portions of the tow which are incompletely or not at all gripped in the nip of rolls 74 and 76 where the grooves occur in roll 76. Thus the filaments in portions of the tow are longitudinally incrementally displaced relative to the filaments in adjacent portions of the tow with the result that the filaments are individually separated longitudinally one from the other. Stated in another manner, the pretensioned tow had been subjected to a mechanical lengthwise separating action by means of the action of rolls 74 and 76.

If the grooves and lands are continuous around the roll 76, the tow emerging therefrom takes on the appearance shown in FIG. 5. If the grooves and lands are discontinuous the tow will have the appearance shown in FIG. 6. In both these figures it will be apparent that the density or number of filaments per unit area is variable across the width of the tow band due to the action of rolls 74 and 76. Thus a roll having continuous grooves will impart a continuous lengthwise ribbed or corduroy effect to the tow as shown in FIG. 5, while a roll having interrupted lands and grooves will impart an elongated checkerboard pattern as shown in FIG. 6. Both figures are reproductions of a photomicrograph of a portion of the tow at a magnification of about 20. Thus, though both types of rolls separate and open the filaments, the action may be incomplete or non-uniform. In other words, where a tobacco smoke filter is produced from a tow in which such incomplete or non-uniform filament separation is present smoke passing therethrough may tend to channel through zones of lesser filament density and the overall effectiveness of the filter may thus be substantially impaired for certain tobacco smoke filter applications, although such channeling may not be objectionable in others. This channeling would be particularly detrimental since it would produce filters having lower pressure drop per unit weight of tow and, therefore, lower tar removal capabilities.

In producing filters by use of plain rolls in conjunction with air jets such as is described in US. patents to Caines et al., 3,099,594, and Dyer et al., 3,079,663, it has been found that certain of the filaments may not separate completely one from another, especially when using fine denier filament tow, e.g., 1.0 to 3.0 denier per filament tows are being processed in accordance with such known processes. Thus careful examination of a filter tip made from fine denier tow by use of air jets and plain rolls to separate to filaments may reveal the presence of occasional clusters of 2 t0 5 or more filaments that have not separated from each other. Filters made from such processes tend to contain clusters of unseparated filaments as illustrated in FIGS 4 and 7. FIG. 4 shows a portion of a banded tow containing such clusters while FIG. 7 shows the presence of such clusters in a finished filter which has been broken open. It is this type of non-uniformity of fiber separation which is present in the finished filter when using prior known methods for treating filter tow. The filter product made by our invention, as described herein, results in a filter having the filamentary structural uniformity necessary to obtain an improved and more effective tar removal performance.

After leaving the filament separating feed rolls 74 and 76 the opened tow is passed through a pneumatic spreading or banding jet 80 which is similar in construction and operation to banding jet 50. The action of this jet is further to increase the width of the band of tow and also to control and maintain its width just prior to application of plasticizer to the tow by its passage through plasticizer applicator 81.

Referring to FIGURE 1, tow 46, after being subjected to the differential pulling action of rolls 74 and 76 as it passes from pretension or drag rolls 58 and 60 and being further banded or spread out to a constant uniform width by passing through pneumatic banding jet 80, is advanced to plasticizer applicator rolls 82 and 84 which are in geared relation to each other and driven by positive means from the main drive (not shown) supported on base 99 of a plug making machine (not shown). The function of these rolls is to transfer a film of liquid plasticizer to both surfaces of the band of tow as it passes between the rolls. The plasticizer employed in a given case will be any suitable liquid plasticizer capable of plasticizing the material of Which the filaments of the tow are composed. For example, if the filaments are composed of cellulose acetate, triacetin would be a suitable plasticizing agent.

As shown in FIGS. 1 and 2, rolls 82 and 84 are slidably mounted within holder frame 90. Each roll is supplied with plasticizer by vertically disposed dual applicators 86 and 88 which are provided with internal liquid plasticizer reservoirs 86A and 88A, respectively. Applicator 86 carries wick element 86B connected to the plasticizer reservoir thereof as shown. Likewise, applicator 88 carries wick element 88B which is similarly connected to its own internal reservoir. Reservoir 86A and wick 86B of applicator 86 are supplied through conduit 93 with a metered amount of plasticizer by means of a metering pump (not shown). Reservoir 88A of applicator 88 and its wick 88B are similarly supplied with plasticizer by means of a separate metering pump and conduit 95.

As shown in FIGS. 1 and 2, wick applicators 86 and 88 are attached, respectively, to positioning means 94 and 92, which may take the form of solenoids or air cylinders which may be actuated in known manner to move applicators 86 and 88 toward or away from rolls 82 and 84 as desired. The lengths of the respective roll contacting surfaces of wicks 86B and 88B are substantially equal to the width of the outlet orifice of banding jet 80 and thus equal to the width of the banded tow passing between rolls 82 and 84.

In operation plasticizer deposited by wicks 86B and 88B on rolls 82 and 84 is picked up by the tow as it passes between the rolls and a film of liquid plasticizer is thus uniformly spread over both surfaces of the tow and into contact with all of the filamentary material of the tow band.

The action of the plasticizer on the individual filaments is to soften or partially solvate the materials of which they are composed, thus rendering them capable of bonding themselves one to another at random points of contact throughout the filamentary mass by coalescence or fusing together of the contacting softened or partially solvated filament material to form a filamentary network. If solid particulate materials such as activated carbon, sodium bicarbonate, rice starch, cellulose acetate fioc, or other additives are placed on the tow to increase the effectiveness of the filter in removing gaseous or solid components from tobacco smoke, in accordance with that embodiment of our invention shown in FIG. 3, these particles are effectively entrapped and firmly held within the resulting filamentary network.

In accordance with the first mentioned embodiment of the invention, the tow, after passing through the nip of applicator rolls 82 and 84, is forwarded to venturi air jet 96 which may be of the general construction and opera tion described in US. Patents Caines et al. 3,099,594 and Dyer et al. 3,081,951. The function of this jet is further to open the tow by completely separating the filaments thereof one from another and to insure uniformity of filament separation by evening out any irregularities in filament distribution which may have resulted from the action of rolls 74 and 76. The action of this jet also serves the important added function of more uniformly distributing the plasticizer throughout the separated filaments of the tow.

The tow will then have a filament distribution pattern similar to that illustrated in FIG. 8 which is a reproduction of a photomicrograph of a portion of the tow at a magnification of about 20. It can be seen that the product has achieved a complete and uniform filament separation which had not been previously possible when using the methods of the prior art. For example, if we were to compare this product as illustrated in FIGURE 8 with the product of FIGURE 4, which is a photomicrograph of a portion of tow as produced by the known method, whereby a 3 denier per filament or less tow is first carried between smooth surfaced feed rolls, treated with plasticizer and then bloomed in a venturi type jet, it will be seen that there is a complete absence of clusters of unseparated filaments in the product of FIGURE 8 as compared to the product of FIGURE 4. A significant comparison can also be made with the product of FIG- URE 7 which is an illustration of a filter, the paper wrap having been broken open to expose the filaments. This product was made by a process employing jet filament separation with an S wrap wiping-type plasticizer applicator of the type disclosed in Us. Patent 3,099,594. Caines et al. also shows the presence of unseparated filaments. These clusters or accumulations of unseparated filaments clearly reduce the effectiveness of the finished filter and is one of the major disadvantages of tobacco smoke filters presently being produced by any of the known methods. This disadvantage is substantially eliminated by the process and apparatus which has been described herein.

In FIG. 3 there is illustrated that embodiment of our invention which includes the step of depositing solid particulate material on the tow prior to actual filter formation. In this modification, the tow is processed by the identical steps employed in processing the tow in accordance with the first modification of the invention as described in detail above up to the point where the tow emerges from plasticizer applicator rolls 82 and 84. The tow may then be passed through a banding jet 104 which serves to further separate the filaments and enhance the uniformity of their separation as well as evenly distribute the plasticizer. The tow is then carried between the pinch of freely rotating guide rolls 106 and 107 and beneath vibratory distributor 108 which deposits on the surface of the moving tow a predetermined amount of a particulate additive material such as activated carbon, sodium bicarbonate, rice starch, cellulose acetate fioc, or other solid particulate material which serve to enhance the ability of the ultimate filter product to remove tars and other solid and gaseous components from tobacco smoke. The tow bearing the particulate material then 'passes to a forming funnel 110 which causes it to. assume a substantial cylindrical shape, thus locking the particulate material within the filamentary mass. The tow then passes between the pinch of delivery rolls 112 and 114, thence into garniture 102 of a filter making machine where it is wrapped in a paper wrap to form the finished filter plug. It will, of course, be understood that the action of the plasticizer deposited on the tow from rolls S2 and 84 7 will be as described above, that is, the material of the filaments at random points of contact will be solvated and caused to coalesce, thus bonding the filaments together at these points of contact to form an open fila- 8 It was surprising to also note that although the plasticizer metering pump speed remained constant, 12.9% by weight plasticizer was measured as being applied to the tow in the process of FIG. 1, while only 9.4% by weight mentary network in which the solid particulate material plasticizer was measured as being applied to the tow by is entrapped. the prior art process.

All of the driven rolls of the apparatus may be con- Thus, some 17% of the plasticizer delivered by the nected either directly or through each other to the main metering pump was lost as drippage and other losses when drive ofthe filter plug making machine and in this manmanufacturing the filters by the process of Sample 1. ner carefully controlled positive speed ratios may be 10 It was further significant that the standard deviation of established between filament separating rolls 74 and 76, the pressure drop of the rods of Sample 2 as made by applicator rolls 82 and 84, delivery rolls 98 and 100 and our process and apparatus of FIG. 1 was 0.616 as comthe tape roll (not shown) of filter forming garniture 102. pared to 1.149 for the Sample 1 rod made by the prior In some cases it may be desirable to insert positive variart process. This is significant because it shows the reable speed devices in the drive trains between the various liability with which our method can produce consistently roll positions so that the tow opening and delivery roll uniform filters as measured by the pressure drop. Not speeds may be adjusted to suit the requirements of a Only are we able to produce a filter having a high pressure given size and type of filter tow to meet certain specificadrop which effectively removes tar from tobacco smoke tions of weight of filter and pressure drop. For further but our process produces filters with a uniformly and convenience, all the apparatus elements may, as shown, standardization which assures the ultimate smoker that be mounted on common-frame 64 so that the entire unit he can expect to receive a more uniform tasting or may be quickly set in place on a cigarette making hi e, flavored cigarette when smoking a particular brand of thus enabling quick conversion from production of tobacfilter cigarette. co rods to filter rods and vice versa without excessive loss The same tow was then processed again on the same of machine time. setup in FIG. 1, except that the plasticizer metering pump In the following examples and description we have set pe d wa u d ab ut 40% to ab ut 43 rpm. Sample forth several of the preferred embodiments of our in- 3 of Table I gives the data of this test result. The filter vention but they are included merely for purposes of rods Were examined hardness and q y of bond illustration and not as a limitation thereof, and found to be at least equal to or slightly better than Exam I the prior art rods of Sample 1. It can be stated that p our process was able to achieve a filter rod which re- A 1.6 denier/filament, 48,000 total denier cellulose quired less bonding agent for a given level of filter rod acetate tow made up of oval cross section filaments was firmness or hardness. used to produce filter rods by employing a process similar From the foregoing and the comparative data it may to that disclosed in Caines et al US. Patent 3,099,594 be seen that the apparatus and process of this invention using jet blooming with an S wrap wiping-type plasticizer makes possible a to 46% reduction in the pressure applicator. The machine operating conditions employed drop standard variation and an improved uniform apand the test results obtained are given under the heading pearance of rods. Since pressure drop is directly related of Sample 1 in Table I below. to tar removal, a similar improvement in tar removal The same tow was then processed on the apparatus of 40 uniformity can be expected resulting in more uniform the present invention as described above and further iltaste and flavor in cigarettes. lustrated in FIG. 1. Details of the machine setup and test results are listed under the heading of Sample 2 in Example II Table I.

Comparison of the tow appearance after treatment The Same tow used Exampl? I Was Processed 9 indicated that the sample 1 tow contained Several square-grooved roll (the mechanical filament separation separated or unbloomed filaments as shown in FIGS. 4 P Such as that disclosed in the Copefiding pp and 7. By contrast, the same tow processed on the apcation of FfitZ 5611 259,352, filed 1963, paratus of FIG. 1 of the present invention was substannow Patent No. 3,255,506 using for Sample 4 (Table I) an tially free of unbloomed filaments and had the appearance 50 interrupted square form groove roll and for Sample 5 of the tow shown in FIG. 8. (Table I) a continuous grooved roll. Machine set-up and TABLE I Sample No l 2 3 4 5 D/F 1.6 1.6 1.5 1.6 1.1; Total denier 48, 000 48, 000 48, 000 48, 000 48, 000 Filament cross section. Round Round Round Round Round Filter length, mm 102 102 102 102 102 Filter circumference, n1m 24. 83 24. 85 24.88 24. 82 24. S2 Plasticized rod weight, grams:

Average .827 .875 .853 764 .805 Standard deviation 019 .021 020 008 .016 Rod pressure drop:

Inches of \iater, average 18.1 18. 0 18. 2 14. 16. 1 Standard deviation 1. 149 0. 616 0. 725 0. 332 0. 617 Hardness, 0.1 mm. penetration:

Average 7. l 6. 2 6. 5 13. 6 9. 0 Range 4. 8-9. 7 4 7-7.9 5.5-7. 4 11 5-15. 5 7 8-10. 5 Percent Plastieizer (Triacetin) 9. 4 12. 9 7.9 7. 3 7. 0 Tow per rod, grams 681 694 709 634 .685 Inches pressure drop per gram of tow 26. 7 26. 1 25 7 23. 4 23. 5 Tar removal 57 57 58 50 53 Speed ratios:

Feed 74/76 to delivery 98/100 1. 39 1. 1. 62 1. 70 1, 31 Feed 74/76 to tape 01102"- 1. 22 1. 33 1. 33 1. 64 1.24 Feed 74/76 to tension 1.45 1.55 1.56 2.35 1. Feed 74/76 to applicator s 84 1.24 1.21 llasticizer pump, r.p.m 72 72 43 filter rod test data are listed in Table I under the appropriate sample number headings.

Visual examination of the bloomed tow of Samples 4 and 5 clearly indicate a less uniform separation and distribution of the filaments (FIG. 6 and 5 respectively) than for the tow of FIG. 8 treated by using the process and apparatus of this invention (Samples 2 and 3 in Table 1).

Examination of the data shows clearly that a lower pressure drop and a lower tar removal count were obtained for the Samples 4 and 5 as produced by the prior art method of mechanical filament separation when compared to Samples 2 and 3 as made by our invention. It was further noted that the tow was used less efiectively by the prior art process since Samples 4 and 5 indicate they have only 23.4 and 23.5 inches of pressure drop per gram of tow, respectively, as compared to 26.1 and 25.7 inches pressure drop per gram of tow for the filter made by our invention, It was further noted that the filter rod hardness was completely unacceptable as required by the trade and that to improve the hardness to an acceptable level considerably more plasticizer or more tow would be necessary. This is economically undesirable.

While it was noted that the uniformity of the interrupted groove roll process Sample 4 was good, this uniformity occured at the cost of lower tar removal count, poorer tow utilization and loss of rod hardness.

While the process and apparatus of our invention has been compared using 1.6 denier per filament oval or substantially circular section cellulose acetate tow, similar results may be obtained when non-circular cross section filament tows with larger or smaller filament sizes and tows of different compositions such as polyolefin, polyamide, polyester or the like are used.

It will be apparent from the above description that our invention has resulted in certain advantages which could not have been achieved by a conventional process and/ or apparatus. We have contributed to the technical advance of our industry by developing a process and apparatus which will produce a better, more economical and more uniform tobacco smoke filter. One such feature of our invention is the manufacture of a tobacco smoke filter which is comprised of a plasticized fine denier per filament tow which is structurally unique as characterized by its complete and uniform filament separation to give no evidence of filament conglomeration. This is a result not heretofore attainable by prior art processes.

Our invention has the additional advantage of manufacturing filters of the type herein described having consistently high tar removal properties. This has been indicated by our comparative data showing the significance of its low standard deviation number. Since pressure drop, uniformity of filament structure and taste of the cigarette to the smoker are all interrelated, it can be readily seen the advantage which results from being able to produce a consistently standardized tobacco smoke filter.

Furthermore, the process lends itself to being easily adaptable to the addition of particulate material within the filter for the more selective removal of certain components of tobacco smoke when it is desirable to do so.

Another outstanding advantage provided by our invention is that by applying the plasticizer to the filamentary material of the tow by depositing the plasticizer from duplex applicator rolls, which conveys it simultaneously to both surfaces of the banded tow, much more uniform distribution of plasticizer is obtained than was possible with prior art methods which involve spraying particles of plasticizer onto the tow or wiping plasticizer onto the tow surfaces. Particulate sprays, for example, tend to form a non-uniform film of plasticizer on the filaments and this results in what may be referred to as a spotted distribution pattern. Such a distribution pattern is unsatisfactory because one portion of the filamentary mass may receive an excess amount of plasticizer while adjacent areas may receive none at all. When employing the prior art wiping method, one segment of the filamentary tow mass may wipe the applicator clean while a segment immediately following may receive no plasticizer at all, thus producing a length-wise intermittent pattern of plasticizer distribution. Moreover, in employing wiping applicators of the prior art, it was generally necessary to snub the tow over the applicator at an angle in order to insure good contact and this was found to result in tensioning the tow to such extent as to remove some of the crimp from the filaments and thus reduce the ability of the tow to produce a satisfactory filter product. In other words, under such circumstances a greater weight of filamentary material and a greater amount of plasticizer was required to obtain a satisfactory filter of given removal efiiciency. All of these undersirable occurrences are avoided by the present invention.

The process and apparatus of this invention have other unique features of novelty and versatility not present in porcesses and tow processing machines of the prior art. For example, in some cases it may be desired to produce a filter product which increases the removal of the phenol component from cigarette smoke. In this case a high molecular weight polyethylene glycol liquid additive has been found to be quite effective and when mixed with plasticizer can be readily applied by our improved apparatus. However, when such a material is added to the triacetin plasticizer, the bonding power and hence the hardness of the filter rod may be impaired. We have found, however, that by applying the polyethylene glycol through one of the wicks of the double roll applicator of the invention to one surface of the tow and the triacetin through the other wick to the opposite surface of the tow that the plasticizing action of the triacetin is not impaired and firm tobacco smoke filter rods with a high phenol removal characteristics can thus be readily produced.

We claim:

1. Apparatus for the production of tobacco smoke filters comprising in combination:

(a) filament separating and feed roll means for 'withdrawing a crimped multifilament tow from a supply package and for mechanically separating the filaments of said tow one from another in a lengthwise direction;

(b) pretension rolls positioned adjacent said feed roll means and adapted to nip and retard said tow being drawn therebet'ween by said feed roll means so that there is a straightening effect upon the filament crimps;

(c) separate banding jet means one in juxtaposition with said supply package and another adjacent said feed roll means, both being adapted to spread and maintain a uniform and constant tow width;

(d) a dual roll applicator positioned adjacent said another banding jet means for applying a thin uniform coating of plasticzer to both spread tow surfaces;

(e) jet treating means adapted to receive the plasticized tow and to further separate the tow filaments and uniformly distribute the plasticizer thereon; and

(f) delivery roll means positioned to receive and advance the tow to a cigarette filter forming garniture.

2. The apparatus of 1 in which said filament separating and feed roll means includes at least one roll having a square-grooved surface that is adapted to coact with another roll having a resilient surface.

References Cited UNITED STATES PATENTS 3,255,506 6/1966 Fritz. 2,794,480 '6/ 1957 Crawford et a1. 15-6-441 3,297,512 1/1967 Cobb et a1 156l66 XR 2,774,680 12/1956 Hackney et al. a 156-299 XR PHILIP DIER, Primary Examiner.

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