US3615997A - Method of making a reconstituted cigarette filter - Google Patents

Abstract

Method of manufacture of cigarette filter elements which permits the utilization of short cuts or staples of the same filamentary tow which is conventionally employed in a continuous fiber form in the manufacture of filter elements. More specifically, these short cuts or staples comprise in total or in part recovered cut fibers derived from salvage bundles of such fibers bound together in the form of porous rod-shaped filter elements. In part longer segments of cut filamentary staple tow which presently accumulate as waste in the manufacture of filamentary bundles are also employed. The method essentially comprises: (1) shredding reject rod-shaped fibrous cigarette filter elements to fracture the bonding therein and separate the short fiber contents into individual filaments which are generally about 20 mm. long; (2) blending a major proportion of the order of 75 percent-95 percent cut fibers from filter element rejects with a minor proportion of the order of 25 percent or less cut staple fibers resulting from waste or random cut fibers accumulated in the manufacture of the filter elements. These latter fibers are normally about twice the length from about 40 to 100 mm.; (3) forming this blend of fibers into a mat of random directional fibers characterized in that the two groups of staple fibers in the blend are physically interlocked with the longer fibers acting as a carrier fiber for the shorter fibers derived from the shredded filter elements; (4) rolling the mat of commingled fibers on a mandrel to shape a lap which is fine picked on a carding machine to reduce the thickness of the mat to a web of fibers which is about 1/16 inch in thickness; (5) adding plasticizer if needed and drawing this web of fibrous material through a rod-forming means capable of transforming it into a continuous circular fiber rod suitable for segmentation into reconstituted cigarette filter elements. In step (5) of the process, the filamentary material may be bonded together more securely by heating, usually with steam, to reactivate or remelt the plasticizer remaining on the reused filter fibers. It is then cured by drying (6) and cooling. If desired, additional plasticizer may be introduced with the steam to further bond the filamentary materials together.

Description

United States Patent [72] Inventor Colin Shaw McArthur Winston-Salem, N .C.

[21] AppLNo. 738,139

[22] Filed June 19, 1968 [45] Patented Oct. 26, 1971 [73] Assignee R. J. Reynolds Tobacco Company Winston-Salem, N.C.

[54] METHOD OF MAKING A RECONSTITUTED [56] References Cited UNITED STATES PATENTS 2,916,038 12/1959 Wade 156/296 X 3,039,908 6/1962 Parmele 156/166 X 3,404,688 /1968 Pinkham et a1. 131/96 X Primary ExaminerCarl D. Quarforth Assistant Examiner-R. L. Tate Atl0rneys Robert S. Dunham, P. E. Henninger, Lester W. Clark, Gerald W. Griffin, Thomas F. Moran, Howard J. Churchill, R. Bradlee Boal, Christopher C. Dunham, Patrick J. Joyce ABSTRACT: Method of manufacture of cigarette filter elements which permits the utilization of short cuts or staples of the same filamentary tow which is conventionally employed in a continuous fiber form in the manufacture of filter elements. More specifically, these short cuts or staples comprise in total or in part recovered cut fibers derived from salvage bundles of such fibers bound together in the form of porous rod-shaped filter elements. ln part longer segments of cut filamentary staple tow which presently accumulate as waste in the manufacture of filamentary bundles are also employed. The method essentially comprises: (1) shredding reject rod-shaped fibrous cigarette filter elements to fracture the bonding therein and separate the short fiber contents into individual filaments which are generally about mm. long; (2) blending a major proportion of the order of 75 percent-95 percent cut fibers from filter element rejects with a minor proportion of the order of percent or less cut staple fibers resulting from waste or random cut fibers accumulated in the manufacture of the filter elements. These latter fibers are normally about twice the length from about to 100 mm.; (3) forming this blend of fibers into a mat of random directional fibers characterized in that the two groups of staple fibers in the blend are physically interlocked with the longer fibers acting as a carrier fiber for the shorter fibers derived from the shredded filter elements; (4) rolling the mat of commingled fibers on a mandrel to shape a lap which is fine picked on a carding machine to reduce the thickness of the mat to a web of fibers which is about l/16 inch in thickness; (5) adding plasticizer if needed and drawing this web of fibrous material through a rod-form ing means capable of transforming it into a continuous circular fiber rod suitable for segmentation into reconstituted cigarette filter elements. In step (5) of the process, the filamentary material may be bonded together more securely by heating, usually with steam, to reactivate or remelt the plasticizer remaining on the reused filter fibers. It is then cured by drying (6) and cooling. If desired, additional plasticizer may be introduced with the steam to further bond the filamentary materials together.

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l2 m/ro SEGMEA/ZS' we use CUAE WITH DRY COOL METHOD OF MAKING A RECONSTITUTED CIGARETTE FILTER BACKGROUND OF THE INVENTION For many years, attempts have been made to manufacture cigarette filter elements which are low in cost yet effective in removal of a substantial amount of tars and nicotine from the smoke of the cigarette. One of the primary factors which has affected the cost of manufacture of such filter elements has been the losses in production runs due to the exacting standards imposed by rigid quality control standards. Normally, the cigarettes manufactured are evaluated for the firmness of the attachment of the cigarette filter element to the tobacco segment of the cigarette. A device described in Sherrill U.S. Pat. No. 2,951,364 is conventionally employed for such testing of cigarette units. In the operation of this device, there is assembled in alignment and tested two cigarettes of conventional length with a double length section of filter material located between the two cigarettes. A band of sealing paper is located around the section of double length filter material and the ends of each of the cigarettes. Compressed air is passed through the unit to test it for any leaks or inadequate bonding of the adhesive between the paper overwrap and the substrate filter element and cigarette body. In those cases where the cigarette unit does not have a satisfactory bond, the entire unit is rejected and the cigarette segment separated from the filter segment. Heretofore the short fibers of the rejected filter elements were not recoverable nor reusable because being normally only about 40 mm. in length, they lacked the strength to be reconstituted as a usable filter rod.

Frances U.S. Pat. No. 2,527,628 discloses blending nonadhesive fibers, such as wool, synthetic rubbers, asbestos fibers and the like with adhesive fibers, such as acrylic fibers, polyamides, cellulose acetate and the like and a fibrous filler such as clay, or talc to act as an inorganic matrix or binder. Cobb et al. U.S. Pat. No. 3,106,501 suggests blending plasticized and unplasticized cellulose acetate fibers in varying ratios with other thermoplastic fibers such as various polyolefins like polyethylene and polypropylene and shaping and compacting the blend in the form of a bundle of fibers into a compacted rod.

Macl'lenry U.S. Pat. No. 2,812,796 suggests a technique of mixing a cellulose acetate staple tow with other forms of staple filamentary material such as polyvinylchloride fibers to form a variety of filter bodies. This blend is said to be useful in the manufacture of such items as filter elements for air cleaners, wick type elements, and the like. In this method, the essential basic raw material employed is staple tow produced in a spinnerette, collected and further processed by means of conventional fiber technology. This staple tow is joined as a bundle with other filaments, wrapped with a cover such as paper, cured, and segmented into filter elements which are normally about 20 mm. in length.

Both staple and continuous filamentary tow of various materials including cellulose acetate filaments have therefore been commonly employed in the formation of bound segments adapted for use as cigarette filters, cigar filters and the like. Generally, the fibers of tow after removal from the spinnerette device are collected in the form ofa folded or neatly arranged bale and held for further processing. The subsequent processing steps normally involve an unwinding or opening up of the raw tow and the separation of the fibers of the tow to provide a relatively thin fiber layer or mat. Sequentially the tensioning of the fibers, crimping, impregnation of the fiber layer with a plasticizer to assist in bonding the fibers together and the formation of a bonded rod follow. This rod is formed by passage of the fiber bundle through a suitable trumpetlike device to change the shape or form of the fibers from that ofa rope or web into that of a continuous porous rod of compressed filaments. in most instances, this rod is heated to further assist in the bonding of the filaments and may or may not be wrapped with a paper overwrap prior to air curing. The final step involves cutting the rod into small segments of the LII order of 20 to 25 mm. in length. Each segment is attached to the end of a cigarette to serve as a smoke filter.

While satisfactory cigarette filters have been made in accordance with the handling and treating techniques generally illustrated above there has been no satisfactory solution to the problem of high quality control losses resulting from the manufacture of filter tip cigarettes by the methods indicated herein.

SUMMARY OF THE INVENTION The invention provides a new and improved method of forming a continuous rod-shaped filamentary rope having fibers therein which are primarily orientated in a longitudinal direction. This rodlike mass is intended to comprise the substance of porous rod-shaped cigarette filter elements. The filamentary mass which comprises the essential substance of this porous rod-shaped cigarette filter gives the outward appearance of a product formed from a continuous tow material. However, as noted above, the filaments which comprise the substance of the porous rod-shaped filter are in fact a composition or blend product generated from cut fibers which have previously been classified as waste because of their short length.

It is a primary feature of the present process that by means of my technique of shredding the reject filter elements, which may or may not be paper wrapped, I obtain individual fiber segments which will interlock physically with one another and with longer cut carrier staple. This enables one to obtain a designed or constructed fiber mass capable of being bonded together into a strong filament rod upon subsequent compaction. To explain this method step more specifically, it must be appreciated that when the reject fiber elements or rods are shredded or torn apart, a fracture occurs at the bonded junctions at which the crimped fibers have been joined within the bundle of filaments which comprise the porous rodlike segments. Once these bundles have been torn open and the individual cut fiber bond fractured and the fiber segments separated out, it will be observed that these short fiber segments have a series of protuberances existent thereon. The protuberance is composed of hardened bonding material. These protuberances correspond to the juncture points where the crimped and randomly connected fibers had previously been adhesively attached to one another. Subsequently therefore, when these fibers are blended together with a minor quantity (5-25 percent) of longer untreated cut staple fibers which act as reinforcement, they interlock or hook at the point of protuberance, and entwine to associate proximately with the reinforcing fiber. The reinforcing fiber thus acts as a spine for the fiber material composite.

Continuing the process from the point of formation of physical blend of cut fiber material, I then prepare a mat of such fiber held together by the interlocking physical characteristics noted above. This mat forming operation initially proceeds in a picker device and subsequently in a carding device which fine picks to reduce the mat to a web. After the mat of fibers, which contains fibers which at this point may still have a random orientation, is thinned out into the form of a thin web of material, the fiber web may be treated with a suitable plasticizer if desired and compressed into a rodlike shape. This rod may be formed by passage of the web through a trumpetlike entrance orifice into a shaping tube or die or preferably through the nip between a series of peripherally grooved wheels or rollers.

In an alternative embodiment of our process invention, the rod-forming chamber is simultaneously subjected to a steam treatment by the injection of steam passing through the tow. This injection may be made through apertures present in a circumferential groove located in the surface of a wheel die as the wheel rotates tomold and shape the rodlike element. The heat of this steam causes the reactivation ofthe protuberances of hardened thermoplastic bonding plasticizer present on the fractured fibers which now acts as an internal bonding cement" carried over into the blend.

While we prefer this process to take place with one set of shaping wheels, the process could just as easily take place with a series of such wheels. if desired, all of these series of wheels could have apertures for the injection of steam to assist in the further bonding of the fibers within the rod-shaped bundle.

Following the shaping of the rod, it may be cured in a number of different ways, which could involve either room or lower temperature cooling of the rod. This may be achieved by its further passage through a plenum chamber or wheel die defined by grooves in the faces of a second pair of wheels or rollers having apertures in the surface thereof whereby the cooling and curing air is injected to hasten the rate of set of the fibrous bonded structure of the rod. This drying step will help to cure the partially bonded joints between the individual compacted short cut strands of fiber. The air drying of the compacted rod will produce a setting of the softened or activated fibers themselves as well as any activator material, i.e., plasticizer, which had been added during or prior to compaction of the mass of fibers in the die into a tightly bound bundle of filaments. This air drying step also produces a hardening of the exterior surface of the rod. This hardening gives the rod increased dimensional stability and in many cases leads to a product which has sufficient flexural strength to be capable of cure without an additional surface coating or wrapping of paper.

in connection with the improved process of this invention, 1 have also made certain improvements in apparatus for obtaining, shaping and curing this new blend of reconstituted cut fibers into a new cigarette filter element. The improved apparatus involved comprises a combination of a means of separating the short cuts of fiber from the rejected cigarette and specifically from the rejected cigarette filter element acting in concert with a means for blending these fibers with other fibers, molding the reconstituted filamentary fiber bundle into a shaped rod and curing the rod. The apparatus combination involved herein is relatively inexpensive to operate and maintain under the rapid production conditions within which it must operate. I

The cigarettes from which the filter elements are to be salvaged are first passed through a device to remove the cigarette paper from the tobacco enclosed within. This device comprises a cylindrical shaped container containing a plurality of vanes. Some of these vanes are mounted on a shaft rotating about an axis extending from container entrance to exit which strike the cigarette bodies to cause the material to impinge upon the inner surface of the container. A plurality of fixed vanes extending inwardly toward the shaft are employed for guiding the material through the container. The fixed vanes and rotating vanes are generally alternated in position and spacing. The rotating vanes are blade shaped and strike the cigarette body without cutting its paper wrapper and also creates a movement of air through the cylinder to aid in material flow through the cylinder to pull out the tobacco from the cigarette without tearing the paper.

There then remains the filter elements and the paper wrapper remaining attached to them which requires separation of the filter elements from the paper wrapper and fracture of the filter element into its individual fiber segments. The filter elements are positioned into an endwise orientation and slit longitudinally in a manner similar to and more particularly disclosed in Pinkham et al. U.S. Pat. No. 3,339,703. The shredding operation which i term this step of the process, involves a mechanical means for chopping the rejected bundle of bound filaments which is in the form of a short rod into individual longitudinally fractured short filamentary segments. Briefly, the shredding of the fiber bundle to separate out the individual short cut fibers involves passing each cigarette filter element into the path of one or more rapidly moving knife blades which fracture the fiber bundle by cutting parallel to the long axis of the filter rod. in a rapid succession of cuts a longitudinal slitting of the fiber bundle is achieved and it is reduced to a mass of cut fibers. FIG. 3 of the Pinkham et at. patent shows a general arrangement of the carrier belt groove which holds the filter element and knife drum which cuts the same upon contact. in my modified shredding device, the carrier belt groove has an additional recess within its concave surface to permit the complete penetration of the cutting blade through the filter rod. By a series of repetitions of this slitting the filter rod is completely shredded into fractured fiber segments about either 20 or 40 mm. long. These fiber segments when so fractured will have a large number of fibers with residual protuberances retained thereon which lend to physical cohesion of the fibers. This mass of fractured fibers is then passed through a conventional hammer mill and huller cleaner to separate out and remove any residual fragments of paper which remain in the mass of shredded fibers.

Following this shredding operation, the cut fibers are passed into a large mixing hopper where a tumbling and rapidly rotating motion blends and commingles a measured quantity of the short fibers with a weighed quantity of reinforcing fibers derived from other sources. The principal source of reinforcing or carrier fibers introduced into the blender-mixer may be random cuttings of short staple fiber which have been discarded in the initial manufacturing operation. The ap paratus which involves the next two steps of my pnocem is conventional to the fiber treating art. The first is the well-known fiber picker which tends to align, open and separate the fibers and form a mat of individual fibers which is about two inches thick and about three feet wide. A carding drum next fine picks this mat into a thin web which is about 1/16 of an inch in thickness and generally the same width as the mat prior to carding.

At this point a conventional plasticizer such as triethyl citrate, dimethyl phthalate, or diethoxyethyl phthalate or the like is simply sprayed on to the web of fibrous material from conventional spray equipment. In some cases especially where the blend of cut fiber staples are rich in reprocessed short fiber segments derived from rejected and bonded filter elements this addition of plasticizer is optional and may be dispensed with entirely.

The next element in our processing apparatus is a forming or shaping die which has prefixed thereto a trumpet-shaped tow or web guide which feeds the web of blended fibers into the nip between a pair of peripherally grooved wheels which synchronously rotate to continuously form a die for compaction of the web of fibers into a shaped rod. These wheels may be apertured for steam injection. it is a significant feature of this shaping apparatus which contains steam injection means that the web of fibers may be simultaneously compressed into a rod while they are contacted with a jet of hot steam which passes through the mass of fibers at the instant they are being compressed into a continuous rod. As a result of this treatment, the residual plasticizer carried over into the blend of fibers on the surfaces of the cut fiber segments derived from the reject filter elements is remelted or reactivated and spreads throughout the compacted rod-shaped molded product.

The porous filamentary rod at this point is relatively soft and flexible. By passage through an air contacting chamber, the rod is cooled and cured into a self-sustaining object. If it is desired not to further process the rod immediately it can be wrapped in paper and slowly cured at room temperature. Preferably however, the rod is cured or set by impingement of cooling air upon its surface in a cooling chamber through which it passes while confined in a central foraminated tube passing through a plenum chamber filled with input dry air forced into the chamber for drying the rod. Alternatively the rod may be passed through a die cavity similar in construction to that where the rod was initially compressed and if desired fluid treated except that the fluid impinging thereon is cool dry air in place of steam.

The impingement of cool dry air on the surface of the rod serves to harden the bonding of the surface oriented filamentary material within the rod as well as accelerate fiber bonding within the interior of the rod. The rod is cut into measured segments by the use of conventional apparatus and attached to a tobacco segment in the conventional manufacturing method.

The product prepared by the operation of the process and apparatus outlined above exhibits certain unique characteristics which distinguish it from filter rods of the prior art. For example. because of its plasticizing treatment, compression and the immediate impingement of cooling air for cure, the rod has (a) a uniform cross-sectional porosity and (b) a congealed yet porous outer layer of bonded filaments which supply rigidity with or without an additional paper wrapping over the rod.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more specifically illustrated by reference to the following preferred embodiment of the process set forth in an illustrative example of its operation. The flow diagram set forth in the drawing will serve to depict the process and outline the various steps. It is understood that this example is in no way intended to limit the concept of the invention which can only be determined by reference to the several appended claims.

The drawing submitted is in the form of a diagrammatic representation of the various steps included in the manufacture of the unique cigarette filter rod of the present invention. For ready reference, each step involved in the process is given a number which, considered in relation to the flow diagram and following the detailed description of the preferred mode of function of the process, will serve to illustrate the relationships existing between the various steps in the process. It will be noted that in some instances a step which is in fact optional is marked accordingly on the flow sheet. This is true with respect to the curing step indicated by numeral in the flow sheet which step represents a rod wrapping procedure in the event the option of slow cure is elected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT EXAMPLE I Eighty-five pounds of filter cigarettes which failed to pass the quality control test because of uneven drawing ability are severed to separate out the filter elements from the tobacco portion. By means of conventional apparatus, the paper cover over the filter element is slit and partially pulled away from its filamentary contents. The ripped elements are milled or shredded as indicated at l to free the paper covers completely from the cut filamentary tow. At the same time this shredding operation fractures the bonds existing between the individual filaments and produces a mass of mixed paper scrap and individual broken filaments about 20 mm. in length. This mass of material is then introduced into a conventional cotton ginlike huller cleaner device as noted at 2 where the fragments'of paper cover are separated from the cellulose acetate cut filaments. This paper is discarded and the remaining reject filaments forwarded for blending with a quantity of carrier fiber. This blending of shorts," i.e., those fracture reject filaments of about 20 mm. in length is accomplished at 3 by mixing pounds of cut staple fibers which vary in length from about 50 to 100 mm. in length and ll; to 4 denier in cross-sectional dimension. In general the blend ratio of shorts with longer reinforcing fibers will vary from about 90 to 75 percent shorts with from about 10 to 25 percent carrier or reinforcing staple. This blending may be accomplished in a conventional Banbury mixer such as a rotating drum with arms or vanes therein which intimately commingles the cut fibers and interlocks the carrier fibers with the protuberances on the fractured reject fibers. The blended mixture is then fed to a picker machine where as shown at 4 the fiber blend is processed into a lap or mat of fiber about 40 inches wide and 2 inches thick. As indicated at 5 this mat is fed to a carding drum or machine to form the fiber blended mat into a thin web of about rte-inch thickness composed of fibers having a random orientation in the web. At this junction the web is guided into a funnel shaped device at 7 where the web is reduced in shape to a generally cylindrical rope of tow. At this point in the operation 5 pounds of triethyl citrate plasticizer'may be sprayed on the web at 6 either before it is shaped into a rope or before it passes into the rotating die wheels at 9.

The web of tow in the shape now of a rope of inch in cross-sectional diameter is passed into the nip between two grooved wheels rotating at a controlled speed of 450 rpm. These wheels are 4 inches in diameter and have a 7.6 mm. diameter groove in each peripheral face.

The tow at this point is converted into a rod of a constant diameter of 7.65 mm. and a moisture content of about 20 percent. This rod is immediately carried to a cooling station 11 where is passes through a plenum chamber circulating cool dry air of about 70 F. temperature and a flow rate through the chamber of 3 cubic feet per minute. This cures the rod which is then passed on to a cutting station I2 where it is cut into cigarette filter rods about to mm. in length.

COMPARATIVE EXAMPLE A As a-means of demonstrating the truly unique character of my process as outlined in example 1 above, an attempt was made to manufacture a cigarette filter rod composed entirely of short cut fibers derived from rejected filter elements.

Thirty pounds of such short fibers, i.e., 20 mm. in length was passed through the huller cleaner in step 2, the picker in step 4, over the carding machine in step 5, formed into a web in step 7.

The product fell apart when it reached the web step and gave evidence of no strength along either its long axis or crosssectional diameter.

The conclusion was thus drawn that the presence of carrier fibers is essential to the success of the operation of the process.

COMPARABLE EXAMPLE B In an attempt to correct the weakness of the product of example A another batch of 20 mm. short fibers was made up into a test cigarette filter element bundle except that this time 9 pounds of finishing liquid was added to the fibrous mass to improve its strength. The results in this evaluation were no better than the results obtained with the preceding fiber mass without the finishing liquid to bind together the fibers.

The conclusion has to be made that to achieve a satisfactory product one must blend the shorts" with at least a minor amount of reinforcing staple fibers of from 50 to about 100 mm. in length.

While in the aforesaid description and examples the short reject fibers are illustrated to have a length of about 20 mm. it must be understood that in those cigarette manufacturing processes where doubles are involved the length of the filter rods will average about 40 mm. in length. These short fibers also must be blended and processed in the manner similar to that illustrated above to produce satisfactory reconstituted fiber rods.

Furthermore, the concept of the invention equivalently extends to the blending of fibers as short as 5 mm. in length which are employed in various types of multicomponent filter elements and may extend out to salvaged fibers which are as long as 25 or 30 mm. in length if salvaged from the process at a point where the cigarette assembly has been segmented into individual cigarettes. If the salvage is made at a point where the cigarette assembly is still intact, the short salvaged fibers may therefore be It), 30, or even 50 mm. in length depending upon the particular type of filter element from which the fibers are salvaged and the point in the manufacturing process at which they are separated out.

What is claimed is:

I. A method for the manufacture of ment which comprises:

a. shreading salvaged rod-shaped fiber-containing filter elements to fracture the plasticizer binding between the fibers making up said filter element and to separate the fibers, the separated fibers having a length in the range from about 5 mm. up to about 50 mm.-,

a cigarette filter ele- 8 i b. blending the separated fibers with cut staple fibers having shaped bundle of fibers while substantially simultaneously a length in the range from about 40 mm. to about 100 heating the formed rod-shaped bundle of fibers; and mm., the resulting blend of fibers separated from said e. curing the resulting formed rod-shaped bundle of fibers. filter elements d h cut staple fib b i d up of 2. A method in accordance with claim 1 wherein the web of about 75-95 percent fibers separated from filter elements 5 fibers has a plasticizer pp thel'em before Web 0f fibers d 25-5 percent fcul staple fibers; is formed into a continuous elongated rod-shaped bundle of c. forming by carding and picking the resulting blend of fibersfib a confinuous web f fib having a thickness 3. A method in accordance with claim 1 wherein the formed about 1 1 inch; rod-shaped bundle of fibers is heated by introducing steam d. drawing the web of fibers through a rod-forming means to 10 mm Contact the fibfls form the web of fibers into a continuous elongated rod-

Claims (2)

1. 2. A method in accordance with claim 1 wherein the web of fibers has a plasticizer applied thereto before the web of fibers is formed into a continuous elongated rod-shaped bundle of fibers.
2. 3. A method in accordance with claim 1 wherein the formed rod-shaped bundle of fibers is heated by introducing steam into contact with the fibers.

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