US2940456A - Fibrous tobacco smoke filter containing finely divided solids - Google Patents

Description

June 14, 1960 G. P. TOUEY FIBROUS TOBACCO SMOKE FILTER CONTAINING FINELY DIVIDED SOLIDS Filed Feb. 8, 1956 F/LAMENTS l/VSOLUBLE PHOSPHATE 0R CARBONATE 0F CIGARETTE WRAPPER George To uey I N V EN TOR.

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ATTORNEXS' United States Patent FIBROUS TOBACCO SMOKE FILTER CONTAINING FINELY DIVIDED SOLIDS George P. Touey, Kingsport, Tenm, asslgnor to Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Feb. 8, 1956, Ser- No. 564,172

Claims. (CL 131-208) The present invention relates to tobacco smoke filtering material and elements thereof suitable for use in cigarettes, pipes, cigarette holders, and cigar holders. In connection with the consideration of the features described herein of spraying plasticizer in droplet form onto the continuous filaments and certain other details, reference may be made to Crawford and Stevens Patents 2,794,480 and 2,794,239.

In the aforementioned patents, newly discovered advantages of a certain type of fibrous tobacco smoke filter are discussed. The filter therein described is prepared from a specially conditioned tow of synthetically spun, crimped continuous filaments and comprises a structurally unitary, elongated rod-like mass of filaments and an annular wrapper encircling the mass, each filament of the mass being substantially coextensive therewith, the filaments being, in the aggregate, substantially parallel to each other and to the longitudinal axis of the mass with at least a large number of the individual filaments having a plurality of short portions thereof crimped into diverging and converging relationship to the main filament axis, a plurality of the filaments having surface solvation bonds to contiguous filaments at random points of contact. Very good results have been obtained in the use of such filters for the removal of nicotine and tars from tobacco smoke, especially in view of the fact that the filters supply other requirements, such as a unitary nature, rigidity, and resiliency, which are equally as necessary to the success of a tobacco smoke filter.

.These filters also have a marked processing advantage over other filters known in the art. However, since the filaments in such filters are generally parallel to each other, some channeling of the smoke through the filter may be possible.

In other words, while a desirable amount of interference with the smooth flow of combustion products through the channels is provided by the random bonds between adjacent filaments, by the incompleteness of filament orientation, and by the short filament portions which are crimped into diverging and converging relationship to .the main filament axis, yet a limited amount of the smoke passing through the filter apparently travels through channels in a smooth, non-turbulent and undisturbed manner and thereby may be exposed to somewhat less than a theoretically maximum amount of impingement upon and contact with the solid surfaces of the filter. Experimental investigations have shown that any attempt to reduce the size or change the shape of the detrimentally smooth smoke channels through the filters by an increase in filter density either through greater compaction of the filament mass or through the use of finer filaments generally also results in an intolerable increase in pressure drop through the filter. It is also unsatisfactory to substantially increase the amount of filament crimp in order to obtain an increase in the amount of smoke impinge- 2 ment by increasing the number of divergent and convergent filament portions. Additional crimp may weaken the filaments to the extent that they will not be able to withstand the tension which is applied to obtain tow bonding according to the Crawford and Stevens method.

In my copending US. patent application Ser. No. 413,- 950 filed March 3, 1954, now Patent No. 2,881,769, of which the present application is a continuation in part, I have disclosed and claimed an improvement based on my discovery that the efficiency of filters of the type described above may be substantially increased without the expected equivalent increase in pressure drop through the filters by preparing the filters with deposits of finely divided solid vegetable starch particles in the smoke channels provided by the spacing of adjacent filaments. The starch particles are carried by and supported on the surfaces of the filaments or fibers.

I have now discovered that a novel additive comprising one of certain inorganic salts provides a filtration efliciency equally as high as the starches and exhibits an advantageous distinction in that it is capable of neutralizing gaseous acids, e.g. acetic acid, contained in the smoke and of serving as a buifering material for maintaining the pH of the smoke in the desired range, i.e. the range of 6.5 to 7.5. I have further found that these salts may be applied as finely divided solids from a slurry in a substantially non-volatile liquid plasticizer for the filament material.

This invention, therefore, has as one object the production of an efficient cigarette smoke filter consisting of a filamentary filtering material, particularly a material comprising an elongated, cylindricalbundle of substantially parallel and longitudinally aligned textile fibers infused with finely divided particles of certain inorganic salts. Another object is to provide means for increasing the efiiciency of a cigarette filter prepared from a textile fiber. A still further object is provision of a filter which is capable of removing nicotine, tars, and other deleterious components of cigarette smoke without causing the smoke to be dry or distasteful. Another object is to increase the efiiciency of tobacco smoke filters of the Crawford and Stevens patents without creating a high pressure drop. A further object is to provide a filter which not only removes particulate liquids and solids from the smoke but also buifers the pH of the smoke. Still another object is to provide a firmly adhering particulate additive for fibrous tobacco smoke filters, particularly those filamentary filters prepared with filaments bonded through a coalescence obtained by means of the application of a spray of a liquid, solvent-type plasticizer. A further object is to provide a method of applying a powdered additive to a fibrous filter through the medium of a spray of a slurry of the additive inn liquid plasticizer. Other objects will be obvious from the present specification and claims.

In accordance with the present invention, the fibers of a pervious fibrous filter mass are made to carry a dispersed deposit of a finely divided, solid, inorganic salt selected from the group consisting of the phosphates and carbonates of magnesium and calcium. Accordingly, the present invention consists, in general, in a fibrous tobacco smoke filtering medium comprising a mass of fibers, the spacing of the fibers providing minute passages for smoke through the mass, the mass carrying therein an additive comprising finely divided solid particles of a water-insoluble inorganic salt of the type described above in an amount of about 5% to about 60% by weight of the fibers plus additive (the concentration not being critical so long as there is suflicient additive present to improve the filtration efiiciency of the filter without creating excessive Patented June 14, 1960- a acidsand carbonic acid.

' itr rs V ama s i J 4."

pressure drop); said particles being supported along the surfaces of and by the fibers and occupying positions along-the walls of and partially blocking said passages whereby a substantial portion of the smoke is impinged on the particles.

' A more specific and very advantageous; embodimentoi' the invention comprises anew tobacco smoke filtering material of synthetically spun continuous crimped.thermo-- plastic filaments and an element made therefrom, the ele-..

. ment comprising a structurally unitary elongated Cylin' 'drical red-like, mass. of. filaments and an. annular wrapper encircling the mass, ea h filament of the mass being substantially coextensive. therewith, the filaments inthe. agaregate eing. n substantial. parallel eac other nd withh -longitudinal. axis ofthe mass bu atleast a-plurality of thefil'aments ea h ha ing e rality of shortfnortions. crimpedj into,diverging and. con verging: relationship. to. the. main filamentjaxisl a'plurality of he filam nts. having; surface. solvation. b nds. to. con.- isu s' filam n fat random pointeot contact,- the. mass arry ng u f rmly di perse therein anj dditive in the amount of' about 5% to about 6.0%.. by weight of the. massplus additive, the additive being. awateninsoluble salt selected from. the group consisting of mag-J u s m nd; c lci m s lts of orth meta-and pyro-phos "Mostadvantageously, the inventioncomprises a filter of cellulese acetate fibers having surfacesolvation bonds" achieyedthrough the application; of a plasticizer spray, the filter carrying uniformly dispersed water-insoluble inorganic salt particles in the amount of about 5 to weight ofjthefilter. 7 I

"Any suitable means known to the art for spreadinga powder. onto. a fibrous surface or through a fibrous mass may beemployed in preparing filters of. the invention. Thus, for eitample, the inorganic'salt powder can be blown onto the fibers, or it. can. beapplied. as. a slurry in water" or in a volatile organic. vehicle. Another method is .to" apply the powder to the fibers electros' tatically,.i ;e. toinduce acharge. on the fibers by friction oeother suitable means and then to runthefibers through archfiinber containing a. highly concentrated cloud of salt dust Preferably this is, done withthefibers or fila-' ments inthe form of a tow :and in. a banded, i.e. spread-: o'titconditionJ Still. another method for applying the salt particles is to. wet the surface of: the filaments with an adhesive or a 'plasticizer before. exposing them to a solids dusting-deizice or other solidsapplicator. The

7 powder. then may. becoutinuously applied to an opened.

atonement mo in ow forme asdescribed in the Crawfor andstevenspatentsf Thatis to say, tow from.

as ugly. roll. i one dto. e undleize-thefilaments and proyide 'a larger and t ere uniform tow cross section, 3. he? pened. tow is Spread uniformly to. a, much.

larger width of e..g., lQ'times its original width, thereby.

Qutfofj fibrousfilterrnasses. generally areinore firmly boun ilapplied inja plasticizerslurry- Also,.by useof gfor; app ica ont f. he olid. it hasbeen possible ,the fiberswith larger; concentrationsof uniformly edand-firmly bound additiye- Employment vof. a.

diluent inertto the powderandto the fiber is. valuable.

in ifacilitating applicationof larger quantities of. additive:

nlastie ae I The invention is illustrated in the accompanying drawings in which: a r 1 a Fig. 1 represents a magnified View of the interior of a mass of filtering material prepared in accordance with the invention, 7 r

Fig. 2 is a view of a cigarette having attached thereto a tip prepared from a filtering material of the invention,

and a Fig. 3 represents aconsiderably magnified view of a section of filaments, such "as alsection of. mamentsnen migrate. into the'surfaoe. of the filaments or o herwise soften on the. surface of'thefil'aments s0. thlatthe.

' powdered additive of thepresentinyention is afiixed to the surface of the filaments at that point." Also, where plas ticizer droplets contact .adiacentI filaments, and crossing filaments, as illustratedfatll, .12 and 13', because of'ithe softening. action of the plasticizerthe filaments will bond to. one another at random points.

: EXAMPLE 1..-MAGNE SIUM; CARBONATE A partially opened tow ofi-a Y crirnpedi regular cross section cellulose acetate yarn. (39.2% acetyl)" having abont eight crimps pet-inch and containing approximately 10,000 filaments of 8 denier per filament was slowly pulled. over a'compressed air bending device as disclosed in the. aforementioned Crawford and Stevens patents and in Jackson, ULS; Patent 2,73'7,68'8, which spread out'the filaments to a width of abouttwelve inches. While the tow was in this spreadcondition it was sprayed using a conventional point spray gun) uniformly with finely-divided droplets of di(rnethoxyethyl) phthalate V plasticizer in order to make numerous portions'of the sur faces of the filaments soft andtacky; The spread tow 'was then passed through a dusting chamber which dusted the fibers uniformly with a finely divided (325 mesh) powder of magnesium carbonate (MgCOQ of a type commercially available from Baker Chemical Co. and designated as analytical grade. On. leaving thedusting chamber the. tow" contained 14% plasticizer and 18% magnesium carbonate, based on the total weight of tow; V carbonate and pla'sti'cizerl After. this spreading; spray ing, and. dusting, the treated tow was pulled baclc to its original shape of a compact-f bundle, i.e. cord, and fed into a conventional cigarette filter plug makingmachine which formed if'cylindrioally, Wrapped it with paper, and cut it intorods- 78 in length and 7.5 mm. in diameter.: The: rods were then given a heat treatment for. one hour atz80f C. to cause. partial solvation: of the. acetate filaments: by the plasticizer'andtherebybond the carbona e parti les to the-filaments: and thefilamentsto each; other, imparting firmness to the--rods. Thereupon;

therodswere readily cut; into. 13. filter tip.lengths.v

ard, brand. available on.the retailrnarket-inthe U.S., The

"cigarettes. were first shortened; by 1.3, and the .13:

machine described by 3. A. Bradford, W. R. Harlan and' H. R. Hanmer in'lndustrial and Engineering Chemistry, vol. 28, pp. 836-9 (1936). The smoke which passed through the cigarettes was collected and analyzed for n cotine and tar content.

Control filters without a powdered additive were also prepared from the same sellulose acetate tow containing the same amount of di(methoxyethyl) phthalateplasticizer. These filters were attached to the same brand of standard king size cigarettes shortened by 13 mm. These cigarettes were also smoked to a total butt length of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content.

- Ten unfiltered king size cigarettes (same brand) which were not shortened by 13 were smoked to a butt length of 35 mm. by means of the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content.

' The results obtained from the three sets of cigarettes are listed in Table I.

Table I Average Pressure Drop, inches mg. Tare Found in the Smoke mg. Nicotine Found in Smoke Cigarettes without filters (85 mm.

length) Cigarettes with cellulose acetate filters- Cigarettes with cellulose acetate-magneslum carbonate filters Pressure drop is expressed above in inches of water at an air flow rate of 17.5 cc./sec. through the cigarette.

EXAMPLE 2.CALCIUM CARBONATE The procedures described in Example 1 were repeated using the same tow of cellulose acetate and the same plasticizer but using in place of the magnesium carbonate a powdered calcium carbonate (CaCO capable of passing through a 325-mesh screen. The treated tow contained 14% plasticizer and 20% calcium carbonate (based on the total weight of the treated tow) as it left the dusting chamber. The baked plugs were cut into 13 mm. filter tips and attached to the standard king size cigarettes which had been shortened by 13 mm. These filtered cigarettes were smoked to a total butt length of 35 mm. on the smoking machine operated under the same conditions as in Example 1, and the smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content.

The collected smoke contained 90 milligrams of tar and 13 milligrams of nicotine. This corresponds to a reduction in tar of 44.6% and a reduction in nicotine of 48.0% due to the filter. The cigarettes had an average pressure drop of 4.3 inches of water.

EXAMPLE 3.-CALCIUM CARBONATE The procedures described in Example 1 were repeated using a tow of cellulose acetate yarn containing 5,000

filaments of 16 denierper filament, a. plasticizer consist-' The treated tow contained 60% cellulose acetate, 30%

calcium carbonate, and 10% plasticizer. A control tow of cellulose acetate yarn of 5,000 filaments, 16 denier per filament, and containing 14% triethyl citrate, was.

also prepared. Both treated tow samples were processed into filter rods and the rods were heated at 60 C. for one hour. Filter tips of 13 mm. in length were prepared from both sets of rods and placed on the standard king size cigarettes which had been shortened by 13 mm. Ten cigarettes containing the calcium carbonate filters and 10 cigarettes containing the control filters were smoked to butt lengths of 35 mm. on the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. a

From the values listed above and in Example 1 it can be seen that the filter containing the combination of acetate fibers and calcium carbonate reduced the amount of tars collected by 29.4% and the amount of nicotine collected by 28.0%. The control filter reduced the amount of tars collected by 4.9% and the amount of nicotine collected by 4.0%. The increase in pressure drop of the filtered cigarette due to the addition of the calcium car bonate to the filter was only about 5%.

EXAMPLE 4.- CALCIUM CARBONATE A tow of regenerated cellulose yarn (viscose) containing 16,000 filaments of 6 denier per filament was spread out to a width of 10 inches and sprayed with a 25% aqueous solution of dextrin glue. While the tow was still spread out and wet with the glue it was passed through a dusting chamber where itrwas uniformly covered with a fine calcium carbonate dust of 0.1 micron' particle size (Multifex MM). On leaving the dusting chamber the tow consisted of 40 parts regenerated cellulose fibers, 30 parts glue (25 solution) and 30 parts calcium carbonate. The combination was pulled back into the form of a compact bundle or cord and fed into a filter-rod making machine which paper wrapped it and cut it into filter plugs 78 mm. in length and 7.5 mm. in diameter. The rods were heated for 1 hour at 100 C. to dry the glue and bond the powder to the fibers. The plugs were then cut into l3-mm. filter tip lengths and attached to mm. standard king size cigarettes which had been shortened by 13 mm. Ten of these cigarettes were smoked to a total butt length of 35 mm. on the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine calcium carbonate, was prepared in a similar manner. The plugs from this tow were heated for 1 hour at C. and cut into filter tips 13 mm. in length. These tips were attached to'85 mm. standard king size cigarettes which had been shortened by 13 mm. Ten of these cigarettes were smoked to a total butt length ,of

animu passed hrough. the cigarettes was collected and analyzed;

' fornicotinh and tar content'.-

Arerage mg. Tats mg; I Pressure Found in Nicotine rop, the Foundin inches Smoke I 'the V I Smoke Clgaretteswith the'regenera'ted fllter' l i (85 mm. length) Y 4:1 j 140' i 21 lose-CaOO; filter (85 mm.'length).. I I

From the. values listed above and in Example 1 it can' be seen that the filter containing the combination ofregen eratcjd, cellulose fibers andcalciurn carbonate-reduced the amount of tars collected by. 38.7% and the amount of nicotine collected by 36.0%. The control filter or re- 'generated cellulose fibers reduced the amount oi tars collectedby 14.1% and the amount of nicotine collected by' ..-Q%-, Th incr asclin thcp ss nrc 4:92.52! t e filtered cigarette due to the addition of the calcium carbonateto thfe'filter-was only about 5%.

EXAMPLE 5.=CALCIUM CARBONATE .A towof cellulose acetate yarn containing...12,090

1 Pressure dro in inches or water at an an new rate 0117.5 e seclina through the cigarette. I V From the results listed above; it can be seen that the filter containing the combination of cellulose acetate fibers and calcium carbonatere'duced theamonnt of tars collected by 44%; and the amount of nicotine collected by- 48%. cellulose acetate fibers hutno calcium carbonate reduced the amount oftarsby only 2.1% andthe. amount of nicotine by althoughits averagefpressiire'drop was filaments; of 5 denier perfilamentwas, spread to a widtlr of'lZinches and'sprayedwith-an emulsioiiconsisting (by weight) of 0.03 part7 sodium lauryl siilfate; I part di(methoxyethyllphthalatc. plasticizen. 2 parts water,. and 3 parts calcium carbonate powder of ultimate particle size of approximatelyo microns. The spread tow was then pulled baclc into acompactbundle or cord and fed into, a cigarette-filter plug. making machinewhich paper wrapped it and cut it intofilter rods 18 in equal to that of the cellulose acetate-calcium carbonate filter.

EXAMPLE A. 1 'UM. CARBQNATE A tow O f cellulose acetate yarn containing 14,000

filaments 6f 5 denier per filament wasspread to a width of 12 inches and sprayed with a suspension of 51% calcium carbonate powder in di(mcthoxyethyl)- phthalate plasticizer containing 33% ethyl alcohol. The calcium carbonate powder hadan ultimate" particl'size of 3microns.

The spread tow was pulledbaclc;intoa'compact bundle at cord and fed into a cigarette finer magmatlength and, 8 11am. in diameter. Therodswer heated;

for minutes at 100 C. to evaporate. the water and to. bond the calcium carbonate firmly to. the fibers by.

means of theplasticizer'. Analyses of the plugs: ihdi'-' cated that they, consisted-of 51% cellulose acetate fibers,

33% calcium carbonate, 5% moisture; and 11% di- (methoxyethyljphthalate' plasticizer. The heated and cooled plugs were quite firm and the calcium carbonate was firmly bonded tothe fibers. The plugs were cut into 13-min. filter tiplcngthsaand attached tdstand'ar'd American king; size: (85 mm.) ci'garette's which had been shortened by 13 mm. Thesefiltered': cigarettes were smoked to a total butt length of 35 mmton'the standard smoking. machine described in Example 1. The smoke whichpassed through-the cigarettes wasv collected and,

analyzed for nicotine and tar content.

A tow. of ccllulose'acetate yarntcontaining 20;000.' fila ments' of 5.- denier per filament was spread to a'width of =11 inches and sprayed with an emulsion consisting:

of20l03; part sodium lauryl sulfate; 1 part di(metlioxy-- ethyl)phthalatei plasticizer; and 2 parts water. tow, containing nocal'cium carbonate, was converted into filter plugs in the. manner described above and the plugs were dried for thirty' minutes. at 100"; C. Analysesof these plugsindicated that they consisted of 84% cellulose. acetate fibers, 12% difmethoxyethyhphthalate plasticizer, and 4%- moisture. The'plugs were cut' into- I3- mm. filter tips and attachedv to ten standard king size cigarettes shortened by l34 mm." These cigarettes. were also. smokedto.totalbuttlenghts of'35 mm. onithersrnoking machine, The smoke which passed. through: the cigarettes? was! collected and: analyzed for nicotineand tar content.

Ten unfiltered? standard kingsize cigarettcsg which not shorteneduby 13' mm. were smokedto a butt length of 35' mm. by'rneansof the smoking machine. Thesmoke which passed through the: cigarettes'was col.- lected and analyzed for? nicotine andjtaiicontent; Thea'results. obtained from the three sets ofi cigarettes: ars-listerhinflfableelk.

s i lfi i cl fiinf i Wfifii t iid cu it fl t fil rods 78 .in length and 8 mlu iil'diamle'tcie Th erode wereheated for thirty minutes at C. to'evaporate the ethyl alcohol and bond the. calcium carbonate powder to the fibe'isby means of'the plasticizer.- Analy; ses ot the" plugs; indicatd that they c'ons'is'ted of 6 5 cellulose acetate fibers, 20 calcium carbonate powder,

and*l3% plasticizer; The heated andcooIed- Iugs were.

quite and the calcium carbanatswagam bonded to the fibers.

rettes which had been sho'r't'e'ned 13f mm. These filtered cigarettes were smoked to'a total'buttlength of 35 mm. on the-standard smoking machine described in Example The smoke which passed-through the cigarettes was collected and analyzed for nicotine andtar content-- I V II I II I The collectedsmokecontained lll mgxof taif and 15 mg. of n'icotine. This corresponds to a reduction-in tar 0t 33'%""and a reduction in nicotine-of 40%" due to 'th'e filter when the, values obtained are compared withthe' unfiltered cigarette values listed in Exarnple 5; The filtered cigarettes had an average'pres'sure drop; of 43 inches ofwater.

EXAMPLE CARBON-ATE A tow otjcellulose acetate yarn containing 14,000'fila-1 ments of 5 denier per filament was spread to E Wldfli' of 12.. inches and sprayed with a suspension of*58% calcium carbonate powder in glycerol tripropionate ::plasticizer. The calcium carbonate'po'wder had an ulti mate particle size-between 7 and l0-"microns'.

The spread tow'wvas pulled back" into a compact bundle or cord and fed into a cigarette filter plug ma'king? machine which pape'r wrapped it and cut it into filter 'rods 78 mm. in length, and'8: in diameter;

Within one hour at room temperature the .rods were rigid and the calciu'rit carbonate'wasfirmly bonded to theifibers. The plugs were cut into 13 mm. filter tips and attached to standard: king size; cigarettes-which; had-been hort- 175,; eneni by 'lheae filteredtcisare es weresrnoked The filter containing the larger number of I The'plugfsf were cut into filter tips and attached to standard Americafi'king size' digzi:

EXAMPLE 8.MAGNESIUM PHOSPHATE 3( 4)2] A row of the type employed in Example 1 was treated as described in that example with magnesium phosphate (325 mesh) rather than magnesium carbonate as employed in Example 1. On leaving the dusting chamber, the tow of fibers contained 14% plasticizer and 18% magnesium phosphate based on the total weight of the combination. Filters were made from this treated tow and fastened to cigarettes which were then test smoked, all by methods as described in Example 1. Analytical data obtained showed that cigarettes with cellulose acetate-magnesium phosphate filters (85 mm. length) had an average pressure drop of 4.2 inches. The smoke contained 98 mg. of tars and 15 mg. nicotine. Comparison of this data with the data obtained for controled filters and unifiltered cigarettes in Example 1 shows that the magnesium phosphate filter reduced the amount of tars collected by 40.0% and the amount of nicotine by 40.0%. The increase in pressure drop of the filtered cigarettes due to the addition of the magne-..

sium phosphate to the fiber was only about EXAMPLE 9.-CALCIUM PHOSPHATE Ca (PO capable of passing through a 325-mesh screen in the dusting chamber. The tow of fibers prepared in this case contained 14% plasticizer and 20% calcium phosphate (based on the total weight) as it left the dusting chamber. The baked plugs were cut into 13-min. filter tips and attached to the standard king size cigarettes which had been shortened by 13 mm. These filtered cigarettes were smoked to a total butt length of mm. on the smoking machine and the smoke which passed through the cigarettes was collected and analysed for nicotine and tar content.

The collected smoke contained 100 milligrams of tar and 16 milligrams of nicotine. This corresponds to a reduction in tar of 38.6% and a reduction in nicotine of 36.1% due to the filter. The cigarettes had an average pressure drop of 4.4 inches of water.

0 EXAMPLE lO.--CALCIUM PYROPHQSPHATE i z a 'zl The procedures described in Example 1 were repeated using a tow of cellulose acetate yarn containing 5,000 filaments of 16 denier per filament, a plasticizer consisting of triethyl citrate, and a powder consisting of calcium pyrophosphate, Ca P O capable of passing through a 325- mesh screen. The treated tow contained 60% cellulose acetate, 30% calcium salt, and 10% plasticizer. A control tow of cellulose acetate yarn of 5,000 filaments, 16 denier per filament, and containing 14% triethyl citrate, was also prepared. Both treated tow samples were processed into filter rods and the rods were heated at 60 C. for one hour. Filter tips of 13 mm. in length were prepared from both sets of rods and placed on the standard king size cigarettes which had been shortened by 13 mm. Ten cigaretes containing the calcium pyrophosphate filters and 10 cigarettes containing the control filters were I0 smoked to butt lengths of 3 5 mm. on the smoking machine. The smoke which passed through the cigarettes was collected and analyzed for nicotine and tar content. Results were as shown in Table III.

Table III Average mg. Tars mg. Pressure Foundln Nicotine Drop, a Foundin inches Smoke the Smoke Cigarettes with cellulose acetate filter mm. lengt 3. 8 155 24 Cigarettes with cellulose acetate- Coal-50 filter (85 mm. length) 4. 2 17 From the values listed above and in Example 1, it can be seen that the filter containing the combination of acetate fibers and calcium pyrophosphate reduced the amount of tars collected by 32.6% and the amount of nicotine collected by 32.0%. The control filters reduced the amount of tars collected by 4.9% and the amount of nicotine collected by 4.0%. The increase in pressure drop of the filtered cigarette due to the addition of the calcium pyrophosphate to the filter was only about 5%.

EXAMPLE 11.CALCIUM DIPHOSPHAT A tow as described in Example 4 was treated and converted into filters as described in that example, except that calcium diphosphate (capable of passing through a 325 mesh screen) was used in place of the calcium carbonate. Rods were made and tested in the same way. They contained 45 parts regenerated cellulose fibers, 30 parts glue (25% solution) and 30 parts CaHPO powder. The filters were evaluated by test smoking as conducted in Example 4 and comparison to control filters and unfiltered. cigarettes as tested in that example. The filters containing the calcium acid phosphate had an average pressure drop of 4.3 inches. and their smoke contained 102 mg. tar and 16 mg. nicotine.

From the values listed above and in Example 1, it can the filtered cigarette due to the addition of the calcium 7 acid phosphate to the filter was only about 5% In carrying out the operation of this invention, the

purity of the carbonate or phosphate employed is not a critical factor. Rather, the form of its particles is more important. The salt should be in a finely powdered form so that it can be readily slurried in a liquid or passed through a spraying nozzle. While the exact size of the particle does not appear to be critical, it is indicated that the salt additive should be at least capable of passing through a 200 mesh screen. Commercial grades of the salts of the invention generally may be obtained in a particle size which will pass through a 325 mesh screen. Advantageously, a salt is used which has at least 80% of its particles of a diameter less than the diameter of the fibers of the filter. For fibers of the size used in the example above, no substantial number of particles should 7 be as large as twice the filament diameter or as small as one-tenth the filament diameter although these limits may ness of the invention extends to other fibrous filters, in-

= r dissoliied 6r plastic material iii'eontigtiofis filament v t are genera'uy dr'ie'nted lengthwi'se of the filter element ver fies 'sjeenrto derive special benefits item the chem at -(2) That where the additive is to whe'r'eby the particles;

surface or superficial su ace' wi V v covered. Itj'isi also most asily; acQOmplished whenthe pb 'srcs v sre e :n rtieu a y-whereit e fibers are with the body of the filter j It; is preferred to' use forfilter;

I preparation in 'accor'danceqwithtthe present invention a continuous strand, e.g. 3,000 to 35,000 filaments, the filaments being of 16' t6 3' deifieri aid having areiir 4 to '10 crimps per; inch, 7

' iQIiPiiIG insubstantial longitudinalalignment and are coextensive v 12.; A tobacco s fioke filter eiemeateemprisiagssufidie, of" continuous 'eiimped cellulose-acetate filaments, a content comprising droplets of plas'tieizer for the fila V-me'nts on said filaments whereby the cio'ntiinitii cellir" i lbselacetatel filaments are bonded to one another at ;By the 'eripressiont fsiii'face solvation as used herein is r V powdered salts to the filaments; the powdered sans being meant the creation; by the action of a solvent or plastigizerand/ or heat,of sanadhesivmtacky ortreadily bond tion of surface portions of mat I, I there is produced a welding adhesion betweetiedja ea e at wea ers w filamfit and e tae aaiens wi ifidw iiito or time with similar 'porti ns e sol atioifhonds between fibersare sometime; d to as fused orffweldedlbonds. y I;

the present S It i to he, no ed that while the filters of pronerties and behayior of the wafer ins'oluble' inorganic salt additives; yet the invention'appears to be equally dependeiit 1115611 the s tructural character of the filter. In this regard, the more important structural factors found in the advantageous form of;- the inyention seem to be:

' I) That me aligned arrears be riiido'mly at fanddnily spaeediriter als. This may be ac ed by tion' before the fibers are spun. L A ,7 fi Pii i df fif a with afiberbonding agent; In other words, no material:

Obviously" no 315 eizefshoulr ljbe'; emplbysea win a detfiiiientalaetion o'n'the'salt particles? (3')"' That'substan ally errat 51; 'pa r ticles'be a off the surfaces ofthe' filenients, supfiort'ed ments, and substantially immobile with respect thereto. This structure is best accomplished by softeniiigof portic'ins of the-filament surf sf witha solvent'of by eer e; atin'g a superficial surfac with a \film formihg material be slightly" embedded, in the t Hein'gfedatedi or:

diameters"- of the particles are not too different from the diameters of the filaments, the major portibnof' the particles being for instance, le'ssi than'twicfe the filament erallyioriejnted lengthwise o'fthefilterelement andiextexidf from endftdend of'th e terel'eiii'en Ja' cofitent of plas'tb' ciz'e'r for. the filaments on said filaments; a vliereb'jf the 7 continuous erirnne d' fil'anients'afe bonded td-oiie Otlieratr'andcEm points of ccintacft and a content ofi a water-insoluble salt powder from the group consistingof-icalcium andt magnesium; salts carried on and by: the continuousfilaments,- said plasticizer also sewing to: bond-"saidmowdere'd salttmthefilamentsa;

- ing condition of the filaments by solution orincipient solual whereby random rioints' ofcontact' and a content er atpowdered salt from the group consisting-of calcium" and magnesium salts carried on and by the continuous, cellulose acetate filaments; the aforesaid 'plasticizer s er ing to bond said characterized in that at least 80% of the particles thereof have a diameter less than the diameter of thecontinuous cellulose aeetatefilaniiits" 5nd ie substantial number of the powdered salt partic es beiii as large as twice the filament diameter or slam as one-rawhide filament or continuous campedcarna e; aeaae filamenfsl'which arid-extend fin i end to and 6f the filter elemenga con tent of filalsticizr the group consisting oi phthalates citr t es} and firopio'nates carried on said filaiii'ents whr'e by the eehti nous cellulose acetate filaments are In tit-one gridthe'r at randpni paints erenfat andja of sanj from the glOilfl consisting of phosphate m alc'iuni and magnesimi'csmed on and by alasalts being male eraiaowder smaller tieize'r serving to beiidsaid 5 of saunas-unheatedsyfimeaq filaments, tm'dr'f 10% of a bonding material eofnp'atible with the 'filameiits icarried Qnjthe filamentsfastdtoplets whereby the filaments 'are bonded at randomgoints without coating of the filainppwdered form from hibl emit er sitar-Tire dionyaii'dflby said filaments, said 1; "d-

ndingithe' salt powdef 'to the fiiarherit's em; is attained.

pfo

' maa siodo'edarmuduswarpe eellulosefacetate' mamas 4 of'iidt statesman 8 denierigerfiIameht which are nrau briemed lengthwise o'fthe filter elementand 7 train end nd o f th'filtje element at least 10% plasticiier fr 1a the rdti onsistia or path -integ a rates; and p fiioiiates earried by said iilamhts at least 26% Qfr were i ia' sr fi @9 1 thepowderedsalt is fromthe group consisting of calcium v and magnesium carbonate; magnesium carbonate. calcium phosphate! magnesium phosphate, 7 ealeium pyro pho sphate mag ies ium pyrophosphatq calcium, metaphosphate and magnesium' 'met-aphos ihate;

about: 8 crimpsper inch, said-filaments carrying. droplets ofiaplasticizer fromthe group consisting of phthalates; t1citrates,-and'propionates,said plasticiaer being present on the filaments in an amount-greater than 1 0-% by weight whereby; the filaments are-bonded to each other atram dom;points 'ofcontact and the pl-asticized filaments carry on their; surface at least- 20% by weight ot a powdered 1 'water'insoluble salt from-the group consisting of, calcium 6: A tobacc'o'smoke filter element onipr'ised (it more.

is water insoliible calcium and magnesium salts" carried on s. A filter element consisting 'ofa bundle; dentist's:- acetate; continuous crimped filaments hav ng at least 9. A tobacco smoke filter element comprising a bundle of continuous crimped synthetic filaments, more than 10% of a plasticizer as a bonding medium carried on the filaments in dispersed form whereby the filaments are bonded at random points, more than 10% of a salt in finely divided form from the group consisting of water insoluble calcium and magnesium salts carried on and by said filaments, said plasticizer also assisting in the bonding of the aforementioned finely divided salts to the filaments whereby an improved filter element is obtained.

10. A tobacco smoke filter element comprising a bundle of continuous crimped cellulose acetate filaments which are generally oriented lengthwise of the filter element and extend from end to end of the filter element, a content of plasticizer for cellulose acetate contained in the filaments whereby the continuous cellulose acetate filaments are bonded to one another at random points of contact, and a content of a finely divided salt from the group consisting of phosphates and carbonates of calcium and magnesium carried on and by the filaments whereby an improved filter element is obtained.

References Cited in the file of this patent UNITED STATES PATENTS 656,649 Landfried Aug. 28, 1900 1,127,771 Jones Feb. 9, 1915 1,784,566 Andrews Dec. 9, 1930 1,936,999 Teague Nov. 28, 1933 1,950,542 Copell Mar. 13, 1934 2,181,614 Striefling Nov. 28, 1939 2,301,159 Drechsel Nov. 3, 1942 2,789,563 Taylor et al Apr. 23, 1957 2,780,228 Touey Feb. 5, 1957 2,805,671 Hackney et a1 Sept. 10, 1957 2,832,351 Hale Apr. 29, 1958 FOREIGN PATENTS 813,324 France Feb. 22, 1937

Claims (1)

1. A TOBACCO SMOKE FILTER ELEMENT COMPRISING A BUNDLE OF CONTINUOUS CRIMPED CELLULOSIC FILAMENTS WHICH ARE GEN-

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