CA1324054C

CA1324054C - Method and device for independently adjusting filter rod density and resistance to draw

Info

Publication number: CA1324054C
Application number: CA000530891A
Authority: CA
Inventors: George Jurkiewitsch
Original assignee: Hoechst Celanese Corp; Hercules LLC
Current assignee: Hercules LLC; CNA Holdings LLC
Priority date: 1987-03-02
Filing date: 1987-03-02
Publication date: 1993-11-09
Anticipated expiration: 2010-11-09
Also published as: GB8705069D0; GB2201879B; FR2613592B1; GB2201879A; FR2613592A1; DE3707527A1

Abstract

METHOD AND DEVICE FOR INDEPENDENTLY ADJUSTING FILTER ROD
DENSITY AND RESISTANCE TO DRAW

Abstract of the Disclosure A method and device for limiting the existing functional correlation between synthetic fiber denier, fiber rod density, and resistance to draw, by replacing bloomed tow with a sliver or nonwoven ribbon maintained under precise constant back ten-sion control within a predetermined range during introduction of the sliver or nonwoven into the garniture of a filter rod-making device.

Description

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5~ ~his invention relates to an improved method for sup-s plying a sliver or a nonwoven ribbon into the garniture of ; ~ a device for making filter elements to remove particulate matter and tars from cigarette smoke, , 5 Conventional methods for making fiber-based filter rods use crimped textile tow of cellulose acetate, or exception-i~ ally a tow of polyolefins such as polypropylene, that has been produced by well-known yarn "opening" mechanisms using air or steam. Binder formulations are then printed or i~ 10 sprayed onto the opened tow and are absorbed between and - into the fibers to adhere them to each other and adjacent fibers.
The tow is then passed into the shaping zone of a filter-rod-making apparatus, which usually includes a gar-}S niture "trumpet" and a garniture, where contact is made -~ - with "tow wrap" supplied from feed roll. The apparatus in-cludes means within the garniture for drawing in and shaping ~- the fibers to form a filter rod, and a cutting device for cutting the rod into individual filter elements ("plugs").
~ 20 cellulose acetate tow can be easily and rapidly pro-; ~ cessed into cuttable filter rods using such standard commer-~ ~ cial filter rod-making equipment. The process is not dele-'#'~; teriously affected by the application of substantial amounts -~ ~ of nonvolatile liquid organic plasticizers such as triace-tin, diacetin, citric acid or the like onto a fiber tow be-fore it enters the garniture of tbe rod making apparatus.
`-~ During the many years that filter rods have been made in the conventional way described, the choice of fibers for such filters has remained generally limited to cellulose 1~2'~.Q ~ -2-fiber tow, which filter elements remain popular even though the resulting elements are not-as efficient as elements ob-tained using synthetic fibers of finer denier (such as poly-olefins) would be. Cellulose acetate fibers are also weaker (1.0-1.2g./denier) than other available fibers, such as polypropylene fibers. ThiS characteristic limits the amount of tension and crimp that can be applied to a fiber tow prior to introduction into a standard filter rod-making ap-paratus, whicb in turn limits the crush resistance, effici-ency and "draw" properties of the filter element.
Synthetic polyolefin fiber such as polypropylene, on ; the other hand, is easily drawn to a much smaller denier that provides improved filter efficiency without loss of the strength needed for crimping and for withstanding the stresses of high speed production.
But polypropylene fibers also have disadvantages. Anopen or "bloomed" polypropylene fiber tow cannot be readily , wet by most cellulose acetate binder formulations, and the -' known formulations fail to provide the anciliary lubricating 20 propertie-~ needed to prevent jamming in conventional high speed equipment unless used in such excessive amounts that filter efficiency and other desirable properties are ad-versely affected. ThiS is particularly true if one also attempts to incorporate as well as plasticizers, appropr-25 iate amounts of modifier components such as humectants, flavors, medicines, absorbents, adsorbents and the like into ~ or onto a fiber tow before the shaping and cutting steps.
6 Besides the problem involving the use of additives with polypropylene fiber tow, a major unsolved problem involves ~ 30 the relationship between pressure drop (resistance to draw) s,~ and dimensional stability or hardness of the resulting fil-ter element. U.S. Patent 4,522,616 (Celanese COrP.), which ~ discloses a high speed process for the preparation of cigar--~ ette filter rods from open fiber cellulose acetate tow, rec-35 ognizes the existence of a complex interrelation between fiber denier, preosure drop and Its effect on draw, filter 1 .. 2 i~

` efficiency, and filter hardness (when cellulose acetate tow is used).
The process of this Celanese patent augments the usual tow-opening steps and so obtains acceptable filter charac-teristics with cellulose acetate tow by by passing the towaround a tensioning roll mounted at one end of lever arm movable around a fulcrum on a supporting frame between the i feed rolls and the rod-making device, the arm being biased in a downward tensioning position by the arm weight distri-. 10 bution, and counterbalanced by adjustable counterweighting.
A constant desired back tension (normally measured in grams) is obtained. The tensioning roll is preferably fixed but - may be a floating roll such as a ~dancer~ roll), to deter-mine the tow width and direction and to impart a degree of ~, 15 tension or ~drag~ ~hat is not however adjustable during operation, and is relaxed before the tow enters the garni-ture.
~; The patent points out that the resistance to air flow through the length of the filter rod (RTD) should be uni-form, since fiber density influences the resistance to air flow. To ensure more uniformity in cellulose acetate tow, ~` U.S. patent 3,960,345 (Rothmans of Pall Mall Canada) dis-closes similar use of a roller, by providing an "inertia-~ less'~ roller on a movable shaft that exerts variable brak-5~ 25 ing pressure against the moving tow before it enters the conical entrance of the garniture, in order to compensate for variations in the density of the tow being fed to the blooming apparatus. Through sensing means, the braking ~- pressure is adjusted to compensate for variations in den-. 30 sity of the tow after it leaves the feed or '~dragll rollers and opening nozzles, so as to maintain a constant tension in the moving opened tow as it moves toward the gripping , rollers that move the tow toward the garniture. The ten-sion is relaxed before the tow enters the garniture.
Neither patent is of course concerned with the effect oE using, irstesd of an opened cellJlose ~etate fiber tow /

., _ of the conventional type, a polypropylene nonwoven or sliver feed (particularly one that contains a variable mixture of fibers and deniers). A feed material of polypropylene sliv-er or nonwoven material, which has a much greater degree of elasticity than cellulose acetate fiber, would not be ex-pected to behave in the same manner (if usable at all) as an opened cellulose acetate fiber tow.
Nonwoven ribbon or sliver of mixed denier and contain-ing polypropylene, either of which is one of the least cost-lo ly form of fiber that might provide the advantage of more ` efficient filtering properties resulting from finer denier, ;~ also eliminate the jamming problem caused by the use of ad--~ ditives with tow. They may include different fiber composi-~!, tions and as well as different deniers, including a low melting fiber such as polyethylene, combined with other polyolefin fibers or cellulose acetate fibers, and provide filters of varying bonding and liquid absorption properties.
Such mixed denier fibers for use in cigarette filter ele-ments will be referred to herein generally as polypropylene mixed fibers.
': To suit the preferences of most users, a smoke filter rod will have a hardness value above about 85~, most prefer-ably about 90%, but should not exceed about 92%. The pres-~ sure drop likewise should not exceed about 350 millimeters -~ 25 of water in a conventional water pressure gauge (defined as -~ mm WG) for typical rods weighing between about 535 and and about 580 9 per thousand.
It is to be noted that the appropriate degree of firm-nes-~ in filter rods made of polypropylene fiber tends to increase the pressure drop and thus interfere with the de-sirable easy "draw" in smoking. In other words, there is a negative correlation between pressure drop or "draw" (Delta P or mm WG) and "hardness value" (%F). (These values are ` based on the use of ~Filtrona Hardness and Resilience and Pressure Drop Testers~ Mark V Series, of the type manufac-tured by Abbey Manufacturing Estates, Wembly Middlesex, Great aritain).

1 ~? 2 i~ J 5 71033-102 ~ An equally deslrable parameter value, whlch ls equally '. difficult to attain with polypropylene mixed fiber, ls "draw ~ unlformlty between fllter elements, namely, a low level of ;v variation in pressure drop. In other words, a low percentage ~ coefflclent of varlatlon or "CV", ln the order of about 7% or A less, is esæential for obtaining high quallty filters.
Thus the use of polypropylene mixed fiber ln a standard .~.
filter rod-making apparatus operating at speeds in excess of 200 meters per minute makes it very difficult to combine a desirable degree of firmness, a desirable easy ~draw" for the smoker, and an essential level of uniformity in these characteristics.
The invention prGvides in an apparatus for making ~; cigarette filter rods that operates at speeds in excess of 200meter# per minute and that includes means for feeding cigarette filterlng material along a feed path, the feed path lncluding a garnlture feed, a tensioning roller for maintaining tension in the filtering material upstream of the garniture feed, the amount of tension being ad~ustable, and means for cutting the filter rods into filter elements, characterized in that the filtering material is a non-woven ribbon or sliver of polypropylene mixed fiber, and the tensioning roller is located between the means for feeding and the garniture feed and is biased toward the feed path to form V-or U- shaped path diverslon around the roller by a bisectlng force ~: that vary from 50 to 200 grams to compensate for variations inmass per unit length of the feed that passes a point up~tream of the roller in a given tlme, the resultant of that force that is ~,~ exerted as a stretching tension on the feed providing a controlled rate of ~ass transfer into the garniture that provides a pre~sure ..
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~ ;~ 2 '~ ~ 6 71033-102 .~ drop not exceeding about 350 mlllimeters of water along the length -........... of a filter element having a circumference of about 24.3 ;~ millimeters and weighing between about 535 and 580 grams per thousand, a hardness value of the filter element between 85 and 92 ^ and a percentage coefficient of varlation in pressure drop value of not above about 7 percent.
r .': From another aspect the invention provides a method for making filter rods, at operating speeds in excess of 200 meters per minute, includlng the steps of feeding cigarette filtering ~ 10 material along a feed path, the feed path having a garniture feed, maintaining tension in the filtering material upstream of the ~: garniture feed, the amount of tension being ad~ustable, and cutting the filter rods into a filter element, characterized in -~. that the cigarette filtering material is a non-woven ribbon or ~ sliver of polypropylene mixed fiber, and the feed path is biased r~
away from its direct path to form a V- or U- shaped diversion by a roller-applied bisecting force that varies from 50 to 200 gramæ to compensate for variations in mass per unit length of the feed that passes a point upstream of the diversion in a given time, said force being applied between feeding of the cigarette ~aterial and the garniture feed, the resultant of that force that is exerted as a stretching tension on the feed providing a controlled rate of mass transfer into the garniture that provides a pressure drop not exceeding about 350 millimeters of water along the length of the filter element having a circumference of about 24.3 millimeters and weighing between about 535 and 580 grams per thousand, a hardness value of the fllter element between 85 and 92, and a percentage coefficient of variatlon ln pressure drop value of not '~

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. 6a 71033-102 .; above about 7 percent.
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Preferably, the percentage coefficient of variation in pressure drop value iæ not above about 4~.
The effect of the tensioning roll in the apparatus and ~ method according to the invention is to establish a unlform and .:~ acceptable rate of mass of feed material entering the garniture, which obviously may require varlatlons from the constant tenslon on the feed required by the Rothmans United States patent ~ 3,960,345.
-~ 10 Exemplary embodiments of the present inventlon are further described ln the followlng drawings, in whlch, .,~.
Figure 1 ls a partial schematic section of a filter-rod maklng system;

Figure 2 is a partial schematic section of a filter-rod making system;

Flgure 3 i8 a partial schematic section of a closed loop ~` system for the automatic ad~ustment of the tensioning device shown ~- in Figures 1 and 2.

The system of Figure 1 has feeding means (24), including ~: 20 back tensioning means in the form of a mounted tensionlng roll ~25) of sufficient width to carry a ribbon of nonwoven -~
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material or a sliver (10) and mounted upstream of the garni-ture (14) of a filter rod-making apparatus (1).
Figure 2 schematically demonstrates a modification of a . filter rod-making system, in which additives (43A) are ap-~ 5 plied, dried, and sandwiched between a plurality of nonwoven ribbons or a ribbon and sliver, and similarly controlled with respect to pressure drop and firmness.
Figure 3 schematically represents a preferred closed ~: loop system for automatic adjustment of the tensioning de-~:: 10 vice shown in Figures 1 and 2, whereby manually adjustable counterweight (34A) Of Figure 2 is replaced with a solenoid (32B), or similar device, electronically activated through a micro- processor and switching means (30B), which is, in -~ turn, responsive to one or more sensing means (31B, 33B and 15 36B) that use conventional measuring means to determine var-iations in the mass transfer rate, the mass per unit length of the feed that passes a given point in a given time.
Referring to Figure 1 in detail, which illustrates a -~c~ manually controlled arrangement that demonstrates that ac-20 ceptable filter elements can be produced according to the ~ invention from a nonwoven ribbon or a sliver of polypropyl-s ene mixed fiber by manual adjustment without automatic feed control, a ribbon of nonwoven material of about 4"-12"
width or a sliver (10) is fed from a feed reel (not shown)~
25 tbrough feed roll (11) and feed and register rolls (12), over guide roll ~17) and around tensioning roll (25) rotat-ably mounted at one end of reciprocally movable lever arm (26) secured at fulcrum (27) to a supporting frame (not - shown), the arm being biased is biased toward the feed path by a force of from 25 to 500 grams to form a V- or U-shaped ' path diversion around the roller in a downward tensioning ` position by the arm weight distribution, and counterbal-s anced, in part, by counterweight ~28) and adjustable coun-terweight ~34) threadably secured on tuning stem (35) to ~- 35 the opposite end of the lever arm. A level of desired ten-ion (ea-ily ~ed-ur~ble in 9rams) is obt~ined by adju-eing ~ 3 2 ~ 8 .
- the counterweight from time to time to compensate for vari-ations in the feed characteristics.
The nonwoven ribbon or sliver (10) is then led over ': guide roll (17) and into garniture trumpet (15) and garni-: 5 ture (14) of filter rod forming apparatus (1), where con-^: tact is made with tow wrap (4) separately supplied from wrap feed roll (5) over support rolls (19), both being fed . onto continuous garniture belt (3); said garniture belt and wrap feed roll are rotatably activated by an electric motor 10 or similar device, not shown, to carry the ribbon (or sliv-er) and tow wrap through the garniture section (2). The ~ conventional rod-making apparatus (1) includes, within the ,: garniture section, (a) means for drawing, shaping and con-~ taining the ribbon (or sliver) to form a plug, (b) means - 15 for wrapping and securing the tow wrap around the plug, and ~'.; (c) cutting means for cutting the resulting filter rods into . individual filter elements (16) of suitable length, which are then transported by packing belt (18) to a receptacle (23).
Figure 2 diagrammatically demonstrates a modification : of the arrangement and process demonstrated in Figure 1, - whereby spray head (41A) and connecting feed line (40A) ~ from an outside source (not shown) uniformly applies a fog i or spray of melt, solution, emulsion or dispersion of one :: 25 or more modifiers and additives (43A) of appropriate concen-tration between two nonwoven fabric ribbon(s) or sliver(s) . (lOA,B) from feed rolls (39A and 42A), whicb are dried in ; register using heated nip rolls (12A) and passed over guide ~;; rolls (17A) before passage through garniture (14A) of rod-:~ 30 making apparatus (lA) to form filter elements (16A) of de-sired length and characteristics. The remaining components s are identically defined by arabic numbers as in Figure 1, except for the suffix "A".
- In the preferred apparatus normally used according to . 35 the invention and shown in Figure 3, the manually adjustable ~ counterweight (35) of Figure 1 is replaces with an automatic "~

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_g_ electronically activated mass transfer rate control arrange-ment shown as a solenoid (32B)-the shaft of which is end-wise secured to lever (28B) whereby density and draw pro-perties of the filter are determined by sensing, at a suit-able point upstream of the garniture (14A), of the mass perunit length of the sliver or nonwoven ribbon feed that passes a given point in a given time, using a combination of conventional optical or other sensing devices, including a micro sensor (31B) and odometer (33B), providing informa-tion that is fed into microprocessor (30B) that controls thetension roll positioning by means of an adjustable contact switch or induction coil (36B). The remaining arabic num-bers denote components similar to those in Figures 1 and 2.
~ A relatively high denier range of fiber can be used ;r- 15 for making acceptable filter elements, since the convention-ally limiting relationship between fiber denier and density and pressure drop can be modified according to the invention by increased control over the nonwoven fabric, or sliver ~, feed component. For instance, a denier per filament (dpf) range of about 1-40 and a bulk tow denier (composite 9000 m weight value of a filament bundle) of up to about 50 X
103, or higher can be used.
Suitable nonwoven fabrics of filaments can be made in by conventional methods, utilizing circular or "Y" cross ..7 : , 25 section fibers, and may include thermal bonded, spun bonded, or needle punched fabrics, the preferred process being a light thermal bonding. They may weigh anywhere within the range of about 5-50 grams/m2 provided they possess suffi-~ cient tensile strength to withstand a tension value not ex-j 30 ceeding about 500 9. A suitable ribbon ~4"-12" width) or sliver may be made up of filaments having a denier within ~i the range of about 1-40 dpf or even higher in the case of nonwoven fabric.
Suitable modifiers, for products obtained in accordance with Figure 2 include, for instance, solutions, emulsions, slspensions or d-spers-ono of one or more humectants gener-( 132;1 ~ J ~

ally exemplified by various polyhydric alcohols such as gly-- cerols, glycols, etc.; flavors-and perfumes such as ketoses and polysaccharides, including wintergreen, spearmint, pep-permint, cinnamon, fruit flavors, etc., and medicines, such as menthol and decongestants.
For present purposes, both the treated and untreated ribbon is conveniently wrapped with regular plug wrap paper having a weight within a range of about 25-90 9/m.2 or higher, as desired.
; 10 While the back tensioning device (i.e. a tensioning roll and counterweight as shown in Figure 1) is biased by J lever arm weight in a downward (positive tension) position ~ with respect to the ribbon or sliver feed, the desired ten-- sion can also be obtained by biasing the lever in the re-,15 verse (upward) direction and placing an apprpriately heavi-er counterweight comparable to (35) on the opposite or ten-sion roll end of lever arm (26).
Depending upon the content and form of the desired fil-ter plug, the tensioning wheel is usefully adjusted to run 20 within a tension force of about 100-200 gm (4.5 dfp 1.5"
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;~; fiber length, 9"-12" width) while a 4.5 dpf continuous fiber sliver requires a tension force between about 50-200 gm to obtain comparable variations in rod density and resistance to draw (RTD). The exact amount, in each case, depends upon ~25 the machine being used and the speed of operation.
t ~For exemplary purposes, the relationships between the amount of tension required on a sliver or ribbon to achieve : , particular filter density, drawing characteristics, and uni-~formity is Çurther demonstrated in the Examples and tables .~.
below.
~ Example 1 - --Slivers of a standard polypropylene feed tow (4.5 dpf) having a bulk denier varying from 58.5 to 66.8 x 103, sub-jected to variations in tensioning force of from 40 (con-trol) to 200 grams, are fed into the garniture of a filter rod-making appar~tus, namely a standard type identified as .j;

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Model MK5, manufactured by Molens PLC, London, England~
which was modified as shown in-Figure 1 to provide appara-tus according to the invention the resulting changes in filter element pressure drop and firmness are noted and the results reported in Table I.
Example 2 Slivers essentially identical to those described in Example 1 ~4.5 dpf) having a bulk denier varying from about 59.8-66.8 X 103 are passed through the filter rod-making apparatus of Example 1, and modified with a back tensioning device (a closed loop device) of the type shown schematical-^' - ly in Figure 3. The test results are reported in Table 2 below.
Example 3 Isotactic polypropylene staple fiber (4.5 dpf and 1.5"
cut) having a "y" cross-section and a flow rate of 40+ 59/10 ~ minutes, is carded into a web weighing about 25 gm/m2.
-~ The web is transferred onto a continuous fiberglass belt and lightly tbermally bonded using a hot diamond-patterned cal-20 ender at 140 C/40 psi roll pressure to obtain a nonwoven fabric which is cut into 12" test ribbon width.
using the test ribbon as feed for the filter rod-making -~ apparatus of Example 1, it is found that comparable changes in pressure drop and firmness are obtained within the range , 25 of about 100-200 gm tension.

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FILTER ROD PHYSICAL PROPERTIES VS. CIGARETTE TOW TENSION
_ CONTROL

Bulk Pressure Drop Firm-. 5 Sample Tension Denier Rwt Circ. P CV ness No. (9) x 103 (9/lOOO) (mm) (mm WG) (~ F) 1 (control) 40 66.8 571 24.17 342 3.9 89.7 2 (Control) 40 66.6 676 24.76 334 3.6 89.4 3 50 66.0 557 24.22 327 4.0 88.7 4 50 66.4 562 24.24 336 4.6 89.3 63.3 549 24.19 325 4.7 88.0 6 50 65.4 564 24.13 339 4.7 88.5 7 50 65.5 554 24.13 339 4.4 88.7 8 100 62.0 548 24.34 290 4.6 85.9 15 ` 9 100 63.5 551 24.28 300 4.5 86.3 100 64.6 553 24.37 302 5.5 86.2 .~' 11 100 62.6 558 24.36 301 3.7 87.1 12 100 63.7 556 24.30 292 3.8 88.7 ~i` 13 150 63.2 549 24.33 289 3.8 85.4 20 14 150 58.8 534 24.18 284 4.0 85.6 150 59.2 529 24.26 280 5.2 86.1 16 150 62.0 534 24.32 279 4.8 85.3 17 150 62.2 522 24.32 278 4.7 85.8 18 200 60.4 537 24.30 278 5.4 85.7 25 19 200 59.8 534 24.29 283 4.5 85.3 200 59.1 534 24.19 288 4.8 85.8 21 200 59.3 536 24.26 275 3.7 84.7 ~ 22 200 59.0 531 24.26 272 4.0 84.3 `$~ ~

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CLOSED LOOP TENSION CONTROL SYSTEM
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Bulk Pressure Drop Firm-Sample Tension Denier Rwt Circ. p CV ness - 5 No. (9~ x 10 (9/lOOO) (mm) (mm WG) (%) (% F) ~`

.' l(**control) 2566.8 580 24.38 355 10.60 89.0 2(**control) 2566.6 575 24.35 350 12.75 87.2 3 50 65.3 58324.37 347 1.03 89.5 ', 4 100 63.6 57524.35 342 1.29 89.2 150 61.0 571 24.32 342 3.32 89.2 6 200 59.8 53524.35 333 7.78 88.5 `~:
`~; *AManual Overfeed Adjustment Example 4 Example 3 is repeated but one nonwoven ribbon is pre-sprayed with a 5% zinc acetate solution for selectively re-moving low-concentrations of cyanide gas. The sprayed ribbon ~; is then dried and a sandwich formed between two ribbons of untreated nonwoven ribbon. Changes in pressure drop and firm-ness are found to be comparable to those obtained in Example 3 upon varying back tension within the range of 100-200 gm.

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Claims

1. In an apparatus for making cigarette filter rods that operates at speeds in excess of 200 meters per minute and that includes means for feeding cigarette filtering material along a feed path, the feed path including a garniture feed, a tensioning roller for maintaining tension in the filtering material upstream of the garniture feed, the amount of tension being adjustable, and means for cutting the filter rods into filter elements, characterized in that the filtering material is a non-woven ribbon or silver of polypropylene mixed fiber, and the tensioning roller is located between the means for feeding and the garniture feed and is biased toward the feed path to form V- or U- shaped path diversion around the roller by a bisecting force that vary from 50 to 200 grams to compensate for variations in mass per unit length of the feed that passes a point upstream of the roller in a given time, the resultant of that force that is exerted as a stretching tension on the feed providing a controlled rate of mass transfer into the garniture that provides a pressure drop not exceeding about 350 millimeters of water along the length of a filter element having a circumference of about 24.3 millimeters and weighing between about 535 and 580 grams per thousand, a hardness value of the filter element between 85 and 92 and a percentage coefficient of variation in pressure drop value of not above about 7 percent.

2. Apparatus for feeding cigarette filtering material into a filter rod-making apparatus as claimed in claim 1, *
characterized in that the percentage coefficient of variation in pressure drop value is not above about 4%.

3. Apparatus for feeding cigarette filtering material into a filter rod-making apparatus as claimed in claim 1, *
characterized in that the tensioning roller is rotatably mounted on at one end of a pivoted counterweighted lever.

4. Apparatus for feeding cigarette filtering material into a filter rod-making apparatus as claimed in claim 1, 2 or 3, *
characterized in that the bisecting force is varied by an electronic mass transfer rate control apparatus that senses the mass per unit length of the sliver or nonwoven ribbon feed that passes a given point upstream of the tensioning roller in a given time and adjusts the counterweight on the lever accordingly.

5. A method for making filter rods, at operating speeds in excess of 200 meters per minute, including the steps of feeding cigarette filtering material along a feed path, the feed path having a garniture feed, maintaining tension in the filtering material upstream of the garniture feed, the amount of tension being adjustable, and cutting the filter rods into a filter element, characterized in that the cigarette filtering material is a non-woven ribbon or sliver of polypropylene mixed fiber, and the feed path is biased away from its direct path to form a V- or U-shaped diversion by a roller-applied bisecting force that varies from 50 to 200 grams to compensate for variations in mass per unit length of the feed that passes a point upstream of the diversion in a given time, said force being applied between feeding of the cigarette material and the garniture feed, the resultant of that force that is exerted as a stretching tension on the feed providing a controlled rate of mass transfer into the garniture that provides a pressure drop not exceeding about 350 millimeters of water along the length of the filter element having a circumference of about 24.3 millimeters and weighing between about 535 and 580 grams per thousand, a hardness value of the filter element between 85 and 92, and a percentage coefficient of variation in pressure drop value of not above about 7 percent.

6. A method for feeding cigarette filtering material into a filter rod-making apparatus, as claimed in claim 5, *
characterized in that the percentage coefficient of variation in pressure drop value is not above about 4%.