US3818863A

US3818863A - Centrifugal spray apparatus

Info

Publication number: US3818863A
Application number: US00119049A
Authority: US
Inventors: R Pierre; M Halpern
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1962-08-14
Filing date: 1971-02-25
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25

Abstract

An improved apparatus for applying liquid state plasticizer to continuous filament tow comprising means for projecting a plurality of plasticizer droplets having a means diameter of 50 to 120 microns against the under side of a web of continuous filament tow at a velocity sufficient to penetrate the tow, thus producing uniform coating of plasticizer on both sides of the tow.

Description

United States Patent 1 St. Pierre et a1.

[4 June 25, 1974 CENTRIFUGAL SPRAY APPARATUS 2,993,468 7/1961 Zmuda et a1 1 18/300 1 Richard Si-Pierre1Melvin 1852332 511325 $332523??? 15 61 81 Helper", both Of Charlotte, NC 3,387,992 6/1968 Arthur et al. 117/1053 [73] Assignee: geganese Corporation, New York, FO PATENTS O P C O 61,430 11/1924 Denmark 299/63 [22] Filed: Feb. 25, 1971 21 V A L N 119 049 Primary Examiner-Louis K. Rimrodt 1 pp Attorney, Agent, or FirmStephen D. Murphy;

Related US. Application Data P l D, Kas Thomas J, Morgan [62] Division of $81. No. 603,372, Dec. 20, 1966, 2 abandoned. 52 us. c1. 118/323 An improved apparatus for pp y liquid State plasti- [51] Int. Cl. Bc 5/02 CiZer t0 Continuous filament Comprising 1 for [58 Field of Search 118/323, 300; 19/66 T; P j g a plurality of plastwizer droplets having a 23/ 2 1/ 3 34 g 9 90; /1 0; means diameter of to 120 microns agalnst the i 117/1053; 299/ 3 under side of a web of continuous filament tow at a V velocity sufficient to penetrate the tow, thus produc- [5 References Cited ing uniform coating of. plasticizer on both sides of the UNITED STATES PATENTS 923,856 6/1909 Kestner 261/90 5 Claims, 7 Drawing Figures l 64 59 .60 1 5a 550 p 57 /2 0 o 1/, o l 7 5317 11% 56 590 530 I 5 0 53 54 50 1 o o o 5 /7 20 5111 U 520 22 33 24= 0 3 i 9 @I 1 I 45 3 t 35 26 i 2.

25 7/ 32 32 /8G 43 a) 19 t W 40 /8a A 47 46 FMENIEU JUN251974 SHEU 1 I]? 3 PAIENTED JUNZSIQM same or 3 IN VEN TOR. R/b/mrd 5/. P/e/re PATENTED 3.818.863

SHEET 3 ur 3 IN VEN TOR.

H56 H'chardSfPMrre fi lm kw Age/7f CENTRIFUGAL SPRAY APPARATUS This application is a divisional application of Ser. No. 603,372, filed Dec. 20, 1966, now abandoned.

This invention relates to the treatment of webs such as continuous filament tow, and more particularly concerns processes and apparatus for the centrifugal spray application of liquid additives thereto.

The main'object of the present invention is to provide centrifugal liquid-spraying processes and apparatus which may be utilized in such diverse applications as the casting of filamentary or fibrous strands, webs and like materials with one or more of a number of different finishes or special purpose compositions prior to the ultimate use of such filamentary materials, thecovering of non-fibrous materials with plastic coatings, etc.

A special object of the present invention is the provision of such processes and apparatus for applying plasticizers and/or other liquid finishes to continuous or staple filamentary materials either in the-form of a coherent web or in the form of loose multi-filament strands such as cigarette tow.

A more specific object of this invention is theprovision of rotatable centrifugal spray means positioned adjacent the path of movement of the web (filamentary or otherwise), to be treated, in association with means for feeding the liquid addendum to the rotatable means.

The ultimate object of the present invention is to provide means and processes for the application of liquids, and particularly plasticizers, to continuous synthetic filament webs whereby cigarette filter rods of enhanced firmness and uniformity can be produced therefrom.

The foregoing and other objects, characteristics and advantages of the processes and apparatus according to the present invention will be more fully understood from the following detailed description thereof when read in conjunction with the accompanying drawings, in which:

FIG. I is a partly schematic, vertical section through an apparatus (viewed from the side) employing a liquid-spraying disc constructed in accordance with one embodiment of the present invention;

FIG. 2 is a front elevational view taken along the line 2 2 in FIG. 1, certainparts being omitted for the sake of clarity;

FIG. 3 is a side elevational view partly in section of a modified spraying disc of the type employed in the apparatus of FIGS. 1 and 2;

FIG. 4 is a diagrammatic illustration of a spraying disc employed in treating a band of filamentary material moving past the disc at one side thereof; and

FIGS. 5 and 6 are similar diagrammatic views of a dual set of such discs as employed to spray liquid on a filamentary material moving past them either at one side of or between the discs.

FIG. 7 is an illustration of a magnified (6):) crosssection of the type of porous disc face material utilized in a preferred embodiment of the invention.

The processes according to the present invention are particularly well suited for use in the application of finishes to synthetic filaments spun through a multiorifice spinnerette the construction of which is well known and per se constitutes no part of the invention herein. Preferably, the filamentary materials may comprise organic derivatives of cellulose such as the esters or ethers thereof, e.g., cellulose organic acid esters such as cellulose acetate, celulose propionate, cellulose butyrate, cellulose benzoate, cellulose acetate formate,

cellulose acetate propionate, cellulose acetate butyrate, and the like, and ethers such as ethyl cellulose. etc. The esters may be ripened and acetone-soluble. such as conventional cellulose acetate, or may be substantially fully esterified, i.e., contain fewer than 0.29 free hydroxyl groups per anhydroglucose unit. such as cellulose triacetate.

' The filaments may, of course, be made of other materials of thermoplastic nature. Examples of these materials are the superpolyamides such as nylon, superpolyesters such as polyethylene terephthalate, polyglycolic acid and copolymers thereof, acrylonitrile polymers and copolymers, polymers and copolymers of olefins and vinyl esters such as ethylene, propylene, vinyl chloride, vinylidene chloride, and vinyl acetate, and the like.

One of the fields in which the processes and apparatus according to the present invention find particular application is in the manufacture of cigarette filters from synthetic continuous filaments of the aforesaid types. In the manufacture of such materials, the filaments, subsequent to their being formed, are combined into yarns or tows, i.e., strands composed of a relatively large number of individual filaments ranging from as few as 10 to as many as several millions. In such contin uous filament tows, the originally more or less straight filaments must be specially treated with, among other things, a plasticizer so as to ensure that the ultimate filter plugs have the desired firmness. In order to facilitate this treatment, it is customary to apply the plasticizer to the filaments by means of spray nozzles or kiss rolls after opening the tow, with the object that the plasticizer must be applied to all the filaments and, as nearly as possible, uniformly to the entire tow.

More specifically, commercial cigarette filter rods are conventionally produced by opening a crimped continuous filament tow by spreading the web and by shuffling or tensioning and relaxing adjacent filaments differentially to deregister the coherent crimped filamentary structure; applying a plasticizer to the opened band of filaments in an amount sufficient to yield a cigarette filter rod of the desired coherence and resistance to lateral compression; and condensing, wrapping and sealing the web in cigarette filter plug form.

While numerous methods and apparatus are known for the continuous application of liquids to filamentary webs and the like, each is in some respects not entirely satisfactory as measured by the rigorous standards of cigarette filter rod production. Optimally, the total amount of plasticizer is minimized to reduce its impact on the organoleptic qualities of the delivered smoke stream, while the coherence and resistance to lateral compression are maintained at acceptable levels. Of particular concern is the reduction of plug to plug variations which reflect the uneven application of plasticizer. Desirably, both the total amount of plasticizer and the amount of plasticizer per bond will remain substantially constant from plug to plug, and the distribution of plasticizer will 'be essentially homogeneous throughout the cross-section.

To achieve these objectives, conventional spray gun applicators discharging small particle size droplets in the range of 5 to 30 microns, preferably below 20 microns e.g., 0.5 to I0 microns, (e.g. US. Pat. No. 3,026,226 to Touey et al.), centrifugal spray means projecting plasticizer droplets at high velocity (e.g. Belgian Patent No. 636,174 issued to Celanese Corp.) or kiss rolls spreading a plasticizer film (e.g. US. Pat. No. 3,255,506 to Fritz), for example, have been conventionally employed with varying and often limited success. t

It has now been discovered that the aforementioned objectives can be successfully achieved in a continuous process meeting commercial quality control specifications by the appropriate selection of plasticizer droplet velocity and particle size delivered by the spray applicator, which is preferably of the centrifugal spray type, most preferably fitted with a rotatable disc having an apertured screen like face of limited porosity, from which the plasticizer droplets are projected.

More specifically, it has been found that bonded cigarette filter plugs exhibiting reduced compressibility and greater uniformity of compressibility values may be readily obtained according to this invention, as compared to rods of comparable circumference, pressure drop and weight prepared by conventional methods at equivalent plasticizer levels. For example, in one series of trials, (specifically exemplified hereinbelow) employing the apparatus of commonly assigned US. Pat. application Ser. Nos. 216,894 and 555,647 of Arthur and Lloyd, filed Aug. 14, 1962 and June 2, 1966, respectively (the entire disclosures of which are incorporated herein by reference), fitted with a conventional centrifugal spray applicator disc (having 16 orifices of one thirty-second inch diameter each about the periphery) and alternately with the spray applicator disc according to this invention, the latter achieved a 9 per cent average improvement in compressibility as compared to the former, together with a 12 per cent reduction in compressibility variation.

These significant improvements are obtained according to this invention by projecting liquid plasticizer droplets of between about 5 and 120, preferably 20 to 60 micron dimensions at a velocity of at least 30ft/sec., preferably at least 50 or even 70ft/sec., in a path intersecting a Web positioned to be treated with said droplets in an adjacent zone, whereby the droplets uniformly coat the available portions of the web. Generally, the web is a tow of continuous synthetic filaments opened to a degree permitting at least some of the plasticizer droplets to pass at least partly therethrough, thereby uniformly dispersing throughout the entire filamentary structure. Most advantageously, an opened filamentary band traverses an at least roughly horizontal plane above the rotating disc member whereby the droplets are projected through the web and fall back thereon.

in a preferred mode of operation the rotatable disc member is constructed with a porous face portion through which the liquid addendum cannot directly or freely pass. That is, the apertuers (provided, for example by a closely woven generally multiple ply wire mesh) are extremely small or define a tortuous passageway, thus preventing the liquid droplets from being projected directly from the interior of the disc in a radial path. Rather, the liquid oozes toward the exterior surface of the rotating disc, and the individual droplets formed are projected largely tangentially from the disc under the influence of centrifugal forces resulting from the rotation. Apparently, the uniformity of droplet size and distribution applied to the web is partly a function of the mechanics of droplet formation and projection thereof in accordance with this invention.

suitable simple porous structure such as a single ply fine wire mesh screen of e.g. 400 mesh (c. 0.00lin. openings) is perfectly suitable. The sintered structures, such as those described in e.g., US. Pat. No. 2,925,650, incorporated herein by reference, are preferred for their excellent mechanical strength capable of resisting the stresses of continuous operation, as well as their high flow capacity.

Surprisingly, the same effect is not achieved by increasing substantially the number of standard disc apertures. Thus, increasing five and six fold the number of one thirty-second inch apertures in a standard disc of the apparatus described in Belgian Patent No. 636,174 still does not yield the improvement in firmness obtained in accordance with this invention. Accordingly, the porous face portion of the rotatable disc is selected with appropriate reference to both the number and size of the apertures or passageways therein.

Preferably, the apertured structure comprises at least 200 up to 10,000 or more pores per square inch of between about 5 and about 120 microns mean diameter. Most desirably, the porous face comprises at least 500 pores per square inch of 20 to 60 microns mean diameter. Suitable such materials are available from Bendix Co. as Poroloy sheet, and from Aircraft Porous Media, Inc. as Rigimesh sintered woven wire sheet. Excellent results have been achieved, for example, with a four ply Rigimesh 12 X 64 (12 and 64 wires per inch of 0.023 and 0.016 inch thickness respectively) sheet of about 0.060 inch thickness having a mean pore opening of 35 microns. A two ply 400 and 100 mesh wire screen combination is also effective.

In accordance with a preferred embodiment of this invention, a tow of from about 2000 to about 75,000 filaments of about 1.6 to l6dpf (having any suitable cross-section and preferably about to about or more crimps per inch) having a total denier of between about 30,000 and about 120,000, which has been opened and deregistered to a band of about 10 to 15 inches is passed through the apparatus depicted in FIGS. 1 and 2 in a generally horizontal plane situated about 4 inches from the circumference of the treating disc at a speed of about 200 to about 500 feet/minute. The disc, formed in portion from the four ply 12 X 64 sintered woven wire sheet described above, is rotated at between about 2000 and 4000 rpm and is supplied with sufficient plasticizer to maintain at least a thin film about the interior periphery of the disc. The plasticizer, generally triacetin (having a viscosity of 28cps at 17C) is forced through the porous surface and is thrown tangentially from the disc (by the centrifugal forces resulting from the rotation) in uniform droplets at a velocity of about 50 to 80ft/sec. The plasticizer droplets impact with the filaments directly or proceed through the web and fall back thereon, homogeneously coating the entire filamentary structure with fine drops of generally less than 75 microns each, the major portion of which fall between about and about microns. The uniformity of application is such that the average variation of compressibility values for a given tow is generally reduced at least 5 percent to a spread not in excess of 15 to 20, preferably less than 10 points. The plugs prepared in accordance with this invention exhibit compressibility values not exceeding 45 with average values preferably less than 30, for a nominal addition of 6 to 7 per cent of triacetin. Corresponding improvements may be evidenced with other bonding systems.

Referring now more particularly to FIGS. 1 and 2, an apparatus 10 is there shown which comprises a housing or cabinet 11 made of any suitable material, preferably stainless steel or the like. The housing 11 has

vertical side walls

12 and 13, vertical front and

rear walls

14 and 15, a floor and a ceiling. The housing floor consists of a pair of

sections

16a and 16b extending toward one another from the lowermost edges of the

side walls

12 and 13 at a relatively gentle downward slope and terminating at a predetermined distance from one another essentially medially of the housing 11, thereby leaving an elongated rectangular opening 17 extending entirely across the housing floor. Arranged below the opening 17 is a well 18 defined by two vertical,

trapezoidal side plates

18a and 18b depending downwardly from the facing edges of the

housing floor sections

16a and 16b, two

slanted end plates

18c and 18d secured to the downwardly converging edges of the

plates

18a and 18b, and a horizontal bottom plate to 18e secured to the lowermost edges of the plates 18a to 18d. The ceiling of the housing 11 is closed and consists of a pair of

sections

19a and 19b extending toward one another at relatively steep slopes from the uppermost edges of the

side walls

12 and 13,

Within the well 18 of the housing 11, a liquidspraying disc 20 is arranged for rotation in a plane which is substantially parallel to and centered between i I the

well side plates

18a and 18b. The disc 20 is essentially shaped in the manner of a narrow mouth cup-like receptacle having an imperforate back plate 21, an annular wall 22 oriented perpendicularly to the plane of the back plate 21, and a front plate 23 having an opening 24 at its center, these elements being supported and separated by spacer bars 25 affixed to the front and back plates, e.g., by screws 26. At least a portion of the annular wall 22 comprises an apertured screen-like sheet 70 providing numerous very small pores or tortuous passageways 7l communicating with the exterior of said disc.

Affixed to the outer face of the back plate 21 of the disc 20 is an axial bushing or sleeve 27 which extends rotatably with slight clearance through an opening 28 in the well side plate 180. The outermost end of the bushing or sleeve 27 receives and is secured forexample by means of a set screw 29 or the like, to the output shaft 30 of an electric motor 31 mounted on and bolted to a platform 32 rigidly affixed to the housing 11, eg by being welded at 32' to the plate 18a and at 32" to the lowermost ends of a pair of angle members 33 rigidly secured, as by welding, at their uppermost ends to the floor section 16a of the housing. It will be understood that the bushing 27 may be connected through the intermediary of any suitable transmission means (not shown) such as gears, sprocket chains or drive belts, to the motor 31, especially if the latter is mounted on a separate supporting structure. The entire apparatus 10 may be rendered portable with the aid of a table mounted on rollers and supporting the housing 11 and the motor 31, as well as other instrumentalities still to be described.

The other side plate 18b of the well 18 is provided with two openings in one of which is mounted a sight glass plug or window 34 through which the operation of the disc 20 can be observed. A short length of externally threaded pipe 35 extends through the other opening, coaxially with the disc, and carries a pair of locking nuts 36 and 37 at the opposite faces of the plate 18b. Connected to the pipe 35 interio-rly of the wall 18 is a nozzle structure 38 the discharge portion 38a of which is oriented substantially at right angles to the axis of the pipe 35. Thus, it will be clear that the pipe 35 and nozzle structure 38 may be adjusted toward and away from the disc 20, with the nuts 36 and 37 serving to lock the nozzle structure in position.

Exteriorly of the well 18, the pipe 35 communicates with a liquid supply or feed pipe 39 which communicates with the pressure side of a metering pump 40 of any suitable type, for example a gear pump. The intake side of the pump communicates with a pipe 41 connected to the bottom of a liquid supply tank 42 into the topof which extends the discharge end of a drain pipe 43 the intake end of which is connected with the wall 18 via a fitting 44 extending a short distance up through the bottom well plate 18e. The projection of the fitting 44 into the well to a distance of about one-eighth inch above the plate 18c forms a trap to inhibit the passage of foreign particles or other solid sediment and impurities into the tank 42. Asssociated with the tank 42 is a reservoir 45, the flow of liquid from the reservoir to the supply tank being achieved through a pipe 46 controlled by a valve 47 the extent of opening of which is controlled by a float 48 adapted to sense the level of the liquid in the supply tank 42.

As hereinbefore described, in accordance with one aspect of the present invention the apparatus shown in FIGS. 1 and 2 is particularly adapted for use in the application of a plasticizer to a moving band of filamentary material, e.g., cigarette tow. To provide passageway for such materials, there are arranged in the

side walls

12 and 13 of the housing 11 a pair of parallel, coextensive, preferably

rectangular openings

49 and 50. A bar 51 of circular cross-section is mounted, through the intermediary of a radial slot 51a, on that part of the wall 12 defining the lower edge of the opening 49 and is secured to the said wall by means of one or more set screws 51b. Similarly, an elongated bar 52 of circular or annular cross-section is mounted, through the intermediary of a radial slot 52a, on that part of the wall 13 defining the lower edge of the opening 50. Secured to that part of the wall 12 defining the upper edge of the opening 49, by means of a slot 530: and set screws 53b, is an elongated bar 53 of circular cross-section to one side of which adjacent to the opposite ends are welded two transversely extending circular bars 54. In like manner, a bar 55 having a slot 55a is secured by set screws 55b to that part of the wall 13 defining the upper edge of the opening 50, and to this bar at one side adjacent the opposite ends thereof are welded two transversely extending circular bars 56. The arrangement is such that the spacings between the bars 54 and between the bars 56 are slightly less than the lengths of the

respective openings

49 and 50. Thus, it will be seen that the various rods or'members 51 to 56 provide rounded edges for the sides of the

openings

49 and 50 so as to prevent any snagging of the filamentary material passing therethrough. Since the opening 49 defines the inlet to the housing 1], the bars 54 are located-exteriorly of the housing, while at the outlet opening 50 the bars 56 are located within the housing. The purpose of the smaller size of the bar 52 will be more fully explained presently.

and 59-60 essentially constituted by flat plates. The

baffles 57 and 58 are welded at their upper ends to the ceiling section 19a of the housing 11, and the

baffles

59 and 60 to the ceiling section 19b. The respective baffles are bent upwardly at their lowermost ends to form troughs or

channels

57a, 58a, 59a, and 60a. The arrangement is such that the troughs of each pair slope downwardly in opposite directions, for example, the

troughs

57a and 60a toward the front wall 14 of the housing, and the

troughs

58a and 59a toward the rear wall of the housing. The function of these baffles will also be more fully explained presently.

Referring to FIG. 2, it will be seen that the front wall 14 of the housing 11 is provided with a relatively large opening 61 which is normally closed by a door 62 and may be opened to provide access to the interior of the housing for repairs, servicing, etc. Opposite the opening 61, the rear wall 15 of the housing is provided with an opening 63 which is covered by a transparent glass or plastic window 64 to permit inspection of the interior of the housing when the same is being used.

Specifically, if the apparatus 10 is to be employed in applying a plasticizer to a cigarette tow, the liquid in the tank 42 and reservoir 45 is composed of any suitable plasticizer composition, such as triacetin, dibutyl 'phthalate, methyl phthalyl ethyl glycolate, or the like. Since the plasticizer must be applied uniformly to the filamentary tow over the entire expanse thereof as well as throughout its entire thickness, the tow is usually passed through a banding jet (not shown) or through a set of grooved tow-opening rolls (not shown) prior to being fed into the applicator chamber defined by the housing 1]. Once the tow has been so opened, it is drawn through the

openings

49 and 50, as indicated by the arrow A, at a predetermined speed between about 50 and 150 meters per minute. At the same time, the

disc is rotated by the motor 31 at a speed between about 1000 and 10,000 revolutions per minute, while the liquid plasticizer is fed by the pump 40 at a rate of about ID to 300grams per minute through the pipe 39, pipe 35 and-nozzle structure 38 into the interior portion of the disc defined between the front plate 23 and the back plate 2B. Due to the rotation of the disc, therefore, the liquid plasticizer is centrifugally forced through the orifices 71 and thrown away from the disc in the form of a zone of fluid droplets disposed essentially in planes which are perpendicular to the axis of rotation of the disc and thus to the path of movement of the tow band. The rate of feed of the plasticizer into the disc, the speed of linear movement of the tow band, and the speed of rotation of the disc are so predetermined in relation to one another that some of those of the plasticizer droplets which are expelled upwardly out of the confines of the well 18 impinge against the bottom of the tow band, while others penetrate through the tow due to the latter having been previously opened. As a result, not only are the filaments located in the bottom and inner regions of the tow band coated with plasticizer, but the uppermost filaments are also so coated since some of those droplets which have sufficient energy to travel entirely through and upwardly beyond the top surface of the band thereafter fall back down onto the top surface of the band. In this manner,

the plasticizer is applied uniformly to all of the filaments in the band. I

The foregoing is diagrammatically illustrated in FIG. 4, wherein the filamentary material or tow band is designated by the reference character M, the droplets of liquid plasticizer by the reference character P, and the spraying disc by the reerence character D.

It is, of course, possible in accordance with the present invention to employ discs the construction of which differs somewhat from that of the disc 20 shown in FIGS. 1 and 2. In accordance with one aspect of the present invention, as shown in FIG. 3, such a modified disc 20a resembles the disc 20 in that it is substantially cup-shaped and provided with circumferentially spaced radial orifices 71 in its peripheral side wall 22'. The front of the disc 20a, however, is substantially closed by a plate 65 which is removably fastened to the inwardly directed flange 66, for example by means of screws 66a and is provided with a central inlet opening 67. The disc 20a is most preferably employed in conjunction with a nozzle 68 (indicated in phantom outline in FIG. 3) arranged within the well 18 so as to direct a stream of the liquid plasticizer horizontally through the opening 67 and into the interior of the disc 20a. The rotation of the disc is effective centrifugally to move the liquid hitting the back plate of the disc radially outwardly of the latter and toward as well as through the orifices 71, whereupon liquid droplets are thrown tangentially from the disc.

It will be understood that although the practice of the present invention has up to this point been illustrated and described as entailing the use of only a single disc, more than one such disc may be employed. This is illustrated diagrammatically in FIGS. 5 and 6. FIG. 5 illustrates a pair of discs D which are disposed in side by side relation, rotatable about parallel horizontal axes, and operative to spray liquid droplets P, in the manner hereinbefore set forth, on a band of filamentary material M passing thereabove. FIG. 6 illustrates a pair of similarly arranged side by side discs D operative to spray the liquid onto a band of filamentary material passing therebetween.

The arrangement shown in FIG. 6 is especially advantageous when the band of material M to be sprayed is relatively dense, or has been previously compacted, or is non-porous or impervious, to such a degree as to prevent the droplets ejected from one disc from passing through the material in the manner illustrated in FIGS. 4 and 5. Thus, the arrangement of FIG. 6 is found to be of great utility in spraying liquid materials, e.g. plastics or the like, onto such bodies as rope, wires, plates, webs and the like which are to be coated with such material on their outer surfaces. It will further be understood that the discs need not rotate in opposite directions as shown in FIGS. 5 and 6, but could rotate in the same direction. Moreover, the axes of the discs need not be disposed in' the same horizontal plane as shown in FIGS. 5 and 6, but could be in a vertical plane or in a plane oriented at an angle to the vertical, and by the same token the material to which the liquid is to be applied need not move in a strictly horizontal path but could move in a vertical or slanted path. Preferably, if two (or even more) discs are employed together, the planes of the discs are somewhat offset relative to one another, to ensure not only that the discs do not spray liquid on one another but also that the respective sheets of droplets do not interfere with one another (as they might if the droplets from one disc hit oppositely moving droplets from another disc). In any multiple disc arrangement, of course, each disc is preferably associated with its own individual liquid-feeding system and nozzle.

compressibility as used herein is determined with a precision deadweight micrometer manufactured by Testing Machines, Inc., Model 55 l. The upper anvil at its highest point is 0.420 inches above the lower anvil. The cigarette filter rod is placed in the center of the lower anvil with the paper seam 90 from the contact point. The upper anvil is released and allowed to fall free onto the rod. The micrometer dial reading is converted to a compressibility value by consulting an empirically derived table which is dependent on the circumference of the rod. A lower value for percent compressibility indicates a firmer rod. Per cent compressa"'aiaattarbhe thirty-second inch, peripherally inch of about micron mean diameter, determined by air flow rates.)

The discs were rotated at a speed of 3600 revolutions per minute. and liquid plasticizer, :in this case triacetin, was pumped to the disc at a rate to provide a uniform application of about 7 percent of plasticizer to the tow.

The results are set forth in tabular form as follows, rods of comparable weight being paired for purposes of comparison:

ibility is the ratio of maximum depression to the diameter of the rod. Average per cent compressibility values referred to herein (often only as compressibility) are the average of 10 determinations taken on separate cigarette filter rod'samples of 60 to 120 mm length. The

recorded values are taken 1 day after processing to permit uniform curing.

The principles of the present invention will be more fully understood from the following examples.

EXAMPLE I In the series of exemplary runs tabulated hereinbelow, an 11 inch band of cigarette filter tow composed of about 13,300 cellulose acetate continuous filaments of Y cross-section, exhibiting about 14 crimps/inch,

having a total denier of 44,000 (3.3dpf) was passed through an applicator chamber constructed substantially in the form of the housing 11 shown in FIGS. 1 and 2, at a linear speed of 265ft/minute.

In each case the cylindrical applicator disc had an disc face has afforded a 12.1 per cent improvement in per cent compressibility variation over all samples (grouping sintered vs. standard values for the six trials) and-a 9.28 percent average improvement in per cent compressibility values themselves (utilizing similar groupings). Comparing rods of equivalent weight, those prepared according to this invention exhibited average per cent compressibility improvements of 8.6,

6.9 and 12 percent respectively. All sintered metal disc a plug compressibility values were below 41.5 and the average value was as little as 30.33.

EXAMPLE II The comparative test of Example 1 was repeated, except that the number of one thirty-second inch outlets in the standard disc 16 were increased five and fix fold to 80 and 96, respectively, and the nominal add-on level of triacetin was six per cent.

outer dlameter of 4.75 inches and about a 1 inch width, The results are set forth below:

TABLE II Run No 7 8 9 Disc. l/32 96 N32" Sintered woven 12X apertures apertures 64 mesh sheet, 35 pore diameter Circumference, mm 24.8 24.8 24.8

Plasticizer, 6.0 6.7 6.9

Compressibility, 34 34 30.8

compressibility range 26.0-38.9 26.0-43.7 27.6-34.0

the sides of the cylinders carrying numerous outlets in the form of small orifices. The comparative A series runs utilized a disc having 16 radial orifices, each with The per cent compressibility values for the multiple apertured standard discs thus did not reflect any marked change from the standard disc, whereas the sintered metal disc again exhibited a low 30.8 per cent compressibility, together with a low range of variation EXAMPLE 111 A paper web (standard white shelving paper) was processed through the centrifugal spray applicator described in Example 1, except that the liquid employed was a tinted plasticizer which appeared on the web in conformance with the application technique (although affected uniformly by the absorbency of the paper, passage through a set of pulling rolls positioned downstream of the treating chamber, and the friction of take up).

The paper section treated with the standard disc, having 16-1/ 32 inches apertures, showed many irregularities of liquid application with considerable variation in droplet size. For example, droplets as large as oneeighth inch appeared in substantial number. A similar disc containing 96 1/32 inches apertures in six rows evidenced some improvement in the ratio of smaller to larger droplets but was also considered unsatisfactory,

The sintered metal disc described in Example I, on the other hand, provided a visibly evident high regularity of small dimension droplets.

EXAMPLE 1V Further trials were carried out in the manner described in Example 1, except that the porous face of the rotatable disc was constructed from a single ply 400 mesh (c 0.0015 inch opening) wire screen, and a double ply 400 mesh to 100 mesh (c 0.0060 inch opening) wire screen combination respectively. Each provided a suitably uniform application of fine plasticizer droplets to the tow.

Although the preceding description has been directed essentially to the spraying of plasticizer onto filamentary material such as cigarette tow, it will be clear to those skilled in the art that the present invention is applicable to the application of a variety of finishes other than plasticizers, e.g., lubricants and anti-static agents, to such materials. Lubricants which lend themselves to the processes of the present invention are, for example, light mineral oil, olive oil, diethylene glycol and the likev Anti-static agents which may be applied in this manner are such substances as mixtures ofdiethylene glycol, water and magnesium chloride in predetermined proportions, oleates and stearates of triethanolamine, and the like. Other additives designed to affect the taste, appearance and related properties of cigarette filters could also be applied by means of the apparatus 10, and the liquid compositions may be colored or colorless. The use of colors may, of course, be of particular importance in operations where impervious bodies are to be coated, for example wires or flat plates.

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

Certain subject matter disclosed but not claimed herein is claimed in commonly assigned and copending application Ser. No. 555,647, filed June 2, 1966, which is a continuation of Ser. No. 216,894, filed Aug. 14, 1962 and now abandoned.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for applying a liquid material to a filamentary material, comprising at least one rotatable cylindrical disc member;

means for feeding said liquid material to and into contact with an inner portion of said disc member;

at least a portion of the annular wall of said disc member being provided with at least 200 apertures per square inch, said apertures communicating with the exterior surface of said disc, said apertures having a mean diameter of between about 5 and microns;

means operatively connected to said disc member for rotating the same at a speed sufficiently high to cause said liquid material to flow under the influence of centrifugal force through said apertures and to be thrown substantially tangentially from said disc member in a path intersecting an adjacent treating zone; and

means for concomitantly advancing said filamentary material through said treating zone along a path substantially transverse to the path of said droplets.

2. The apparatus of claim 1, wherein said apertured surface of said rotatable disc member comprises a woven wire screen of at least 400 mesh.

3. The apparatus of claim 1, wherein said apertured surface of said rotatable disc member comprises an at least two ply sintered woven wire sheet of at least 500 pores per square inch, said pores having a mean diameter of between about 20 and about 60 microns.

4. The apparatus of claim 3, wherein said apertured surface comprises a four ply sintered woven wire sheet of about 750 pores per square inch, said pores having a mean diameter of about 35 microns.

5. In apparatus for centrifugally applying liquid plasticizer to continuous filament tow comprising a generally cylindrical rotatable disc member having an annular wall with apertures therein communicating with the exterior surface thereof, the improvement which comprises providing said apertured surface with at least 200 pores per square inch, said pores having a mean diameter of between about 5 and about 120 microns.

Claims

1. Apparatus for applying a liquid material to a filamentary material, comprising at least one rotatable cylindrical disc member; means for feeding said liquid material to and into contact with an inner portion of said disc member; at least a portion of the annular wall of said disc member being provided with at least 200 apertures per square inch, said apertures communicating with the exterior surface of said disc, said apertures having a mean diameter of between about 5 and 120 microns; means operatively connected to said disc member for rotating the same at a speed sufficiently high to cause said liquid material to flow under the influence of centrifugal force through said apertures and to be thrown substantially tangentially from said disc member in a path intersecting an adjacent treating zone; and means for concomitantly advancing said filamentary material through said treating zone along a path substantially transverse to the path of said droplets.