US3396061A - Smoke filters - Google Patents

Description

6, 1968 c. L. BROWNE 3,396,061

SMOKE FILTERS Filed June 1, 1964 Unit 3,396,061 SMOKE FILTERS Colin L. Browne, Charlotte, N.C., assignor to Celanese Corporation, a corporation of Delaware Filed June 1, 1964, Ser. No. 371,248 13 Claims. (Cl. 156-178) ABSTRACT OF THE DISCLOSURE This invention relates in general to improved tobacco smoke filters and to methods of producing such filters.

Cellulosic tobacco smoke filters, made for example of tissue or crepe paper or of rayon (regenerated cellulose) filaments, have the advantage of high smoke removal efliciencies at acceptable pressure drops across the filter. Pressure drop and smoke removal efiiciency are conventional properties in the tobacco smoke filter art. The method of measurement may vary slightly from manufacturer to manufacturer but with inconsequential effect on the finally assigned values. Applicant makes pressure drop and smoke removal efiiciency measurements by the procedures set forth in US. Patent No. 3,103,220.

An example of the high smoke removal efiiciencies that may be attained by the use of cellulosic filters are the cellulosic cigarette filters described in US. Patent No. 2,954,036. A conventional length filter tip (i.e., about 17-25 mm.) made by the process described in said patent has a smoke removal efficiency as high as about 75% while having a commercially acceptable pressure drop of not more than about 90 mm. of water.

However, cellulosic filter media have the disadvantage of excessive moisture pick-up from the smoke stream which results in unsatisfactory taste or excessive heat and smoke dryness.

Cellulose acetate, another common tobacco smoke filter medium, does not excessively pick up moisture and has satisfactory taste. However, cellulose acetate does not have as high a smoke removal efiiciency as cellulosics.

Commercially used are tobacco smoke filters, e.g., cigarette filter tips, which are a compromise between the high smoke removal efficiency of coliulosics (by cellulosics is meant various forms of cellulose such as rayon filaments and paper and not cellulose derivatives such as cellulose ethers or esters) and the pleasant taste of cellulose acetate. Such cigarette filters generally are dual component, comprising a segmented filter with the segment (component) which is at hte smokers mouth being cellulose acetate and the segment (component) which is immediately adjacent the tobacco being a cellulosic. Either or both components may contain a flavoring agent such as menthol or an agent such as carbon which selectively filters from the smoke certain undesirable ingredients thereof, e.g., phenolic compounds.

A major disadvanage of dual component cigarette filter tips is that each production line requires two filter rodmakers, one for the cellulosic and one for the cellulose acetate and, furthermore, there are, accordingly, additional operations such as cutting discrete component (1 States Patent 3,396,061 Patented Aug. 6, 1968 lengths from two different sources and uniting the two components and in a single wrapper.

It is an object of the present invent-ion to make tobacco smoke filters which combine the relatively high smoke removal efiiciency of cellulosics and the pleasant taste of cellulose acetate but which do not have the disadvantage of the multiple assembling operation required in dual component filter tips of the usual type.

Further objects will be apparent from the following description and claims.

In the drawings:

FIG. 1 is a schematic illustration of a method embodiment of the present invention.

FIG. 2 is an illustration of a product embodiment of the present invention.

According to the present invention, there is provided a tobacco smoke filter comprising two webs (the term web herein being used to include tows) preferably a cellulosic web and a cellulose acetate tow, condensed together. Preferably the cellulosic web is paper (e.g., tissue or crepe paper) because it is especially inexpensive and easy to handle. However, any other cellulosic web, such as a tow of rayon filaments, may be used to advantage. Preferably, the cellulose acetate tow is a deregistered tOW.

The cellulosic web may be disposed centrally relative to the cellulose acetate tow or the cellulose acetate tow may be disposed centrally of the cellulosic web. The flow resistances of the cellulosic and cellulose acetate filter components should be balanced so as to give the proper balance of filtration between the two media. This is to give the most desirable taste and required filtration appropriate to the tobacco or tobacco blend employed in the cigarette. The balance of flow between the filter media may be adjusted by varying the relative weights of the components, the cross sectional configurations of the components, the composition or consistency of any fluid or the composition or particle size of any solid which may be added to either or both components for purposes of selective smoke removal and/or flavoring and/or bonding or by varying combinations of any of the above. By way of definition, where one filter material is centrally disposed relative to the other the former filter material is said to constitute a core and the latter filter material is said to constitute a sheath.

Another relative disposition of the cellulose acetate tow and cellulosic web which is provided according to the present invention is that the cellulose acetate tow and the cellulosic web may each be substantially in the configuration of a helicoid with the helicoids concentric and in face-to-face relationship. In the present specification and claims, the term helicoid denotes a three-dimensional figure having the form of a flat coil or flattened spiral.

In all of the filters of the present invention, generally it is preferred that the cellulose acetate tow and cellulosic web be interfacially cohered. In the absence of this feature: there often will be lower density of filter material in the neighborhood of the boundary between the two different materials as compared with the balance of the filter due to imperfect joining together of the two materials and smoke will tend to preferentially flow through the resultant spaces (this is known as a channeling effect); furthermore, a cigarette filter tip so constructed sometimes will be deficient in firmness sufficient to prevent excessive cross-sectional deformation of the tip when handled or when between the smokers lips. Channeling and/ or lack of firmness can also be overcome by increasing the total weight of filter media used so as to cause higher internal pressure within the filter rod or tip sufficient to collapse said spaces.

The interfacial coherence may satisfactorily be attained by the application of adhesive at the prospective interface (i.e., to the surfaces of either the cellulose acetate tow or the cellulosic web or both which will comprise the interface) or by the plasticization (with plasticizer and/ or heat and/or solvent) of the cellulose acetate tow and/or the cellulosic web at the surfaces which will comprise the interface. Since by the use of the plasticization method excellent coherence generally is not attained unless both the cellulose acetate tow and the cellulosic web are plasticized, this method is not preferred because the plasticization of cellulosics is difiicult of attainment and the simultaneous plasticization of both filter materials by the same treatment, which would be the most efficient mode of operation, is not practicable. Thus, the use of any efifective adhesive (such as starch, polyvinyl alcohol and polyvinyl acetate emulsions or other adhesive emulsions, suspensions, pastes, solids or fluids and the like) is preferred, especially when applied to the surfaces of both materials which will comprise the interface whereby especially excellent coherence is attained.

In order that each of the cellulose acetate and cellulosic contribute substantially to the properties of the filter, the minor component should make up at least about by weight of the total weight of both materials. It is preferred that the minor component be no less than about 30% and most preferred is a 5050 product.

As with the conventional dual component filters previously referred to, either or both filter materials may have applied thereto or incorpormated therein bonding and/or flavoring and/or selective filtering agents. Any known method of applying or incorporating such agents may be employed.

Also constituting part of the present invention are improved methods of making tobacco smoke filters whereby the tobacco smoke filters of the present invention may be made. In general, such improved methods comprise bringing together two webs, preferably a cellulosic web and a cellulose acetate tow, condensing together said two webs in the form of a single continuous rod and dividing said continuous rod (in one or more, preferably two, operations) into a plurality of discrete lengths, said discrete lengths comprising the improved tobacco smoke filters of the present invention.

More specifically, a method of the present invention comprises simultaneously feeding to the garniture of a conventional cigarette filter rod-maker a cellulosic web, preferably paper (e.g., tissue or crepe paper), and a cellulose acetate tow, preferably which is crimped and deregistered, condensing said web and said tow in said garniture thereby shaping them into a single continuous rod and dividing said continuous rod into a plurality of discrete lengths, said discrete lengths comprising the improved tobacco smoke filters of the present invention.

As previously explained, it is preferred that the cellulosic web and cellulose acetate tow be interfacially cohered. For example, a polyvinyl alcohol adhesive may be padded from an aqueous emulsion onto the cellulosic web and/ or the cellulose acetate tow immediately before said web and said tow are brought together: thus, the web and/ or tow may each be passed over and in contact with a rotatable absorbent (e.g., felt-surfaced) roll which is partially immersed in a bath of the emulsion. Or, for example, immediately before the cellulosic web and cellulose acetate tow are brought together, the cellulosic web may be plasticized by being passed through a chamber containing superheated steam and/or the cellulose acetate tow may be plasticized by being sprayed with a mist of glycerol triacetate, triethyl citrate or other common plasticizer.

Alternatively, instead of being rendered mutually coherent immediately before being brought together, the cellulosic web and cellulose acetate tow may be cohered before being fed to the condensing operation and thus be fed from a single source and as a single composite structure (for example, from a roll of the pre-cohered composite structure). Otherwise, the cellulosic web and cellulose acetate tow are fed from individual sources (e.g., the tow from a bale, using any conventional cigarette filter tow withdrawal system, and the cellulosic web, viz. paper, from a non-driven, rotatable roll, using driven rolls which contact the web to withdraw it from the roll).

The filter material which it is desired to dispose centrally relative to the other filter material is fed into the trumpet of the garniture by means of a truncated conical funnel guide of substantially smaller exit diameter than the width of said filter material, which funnel guide gathers said filter material into a bundle and directs the bundle into the center of the other filter material. When such a funnel is not used or when the two filter materials are fed as a single composite structure, previously described, the two filter media when passed throughv the garniture may tend to assume a relative disposition wherein each is substantially in the configuration of a helicoid, said helicoids being concentric and in face-toface relationship.

Methods of deregistering a conventionally crimped cellulose acetate tow are well known and any such method may be used complementary to the present invention. Similarly, any conventional method of plasticizing cellulose acetate tow for the purpose of bonding the filaments of said tow to one another may be conventionally employed before the garniture and thus serve a dual function in the present invention by also rendering the surface of the cellulose acetate tow adherent with respect to the surface of the cellulosic web. However, it will sometimes be found desirable to employ supplementary plasticization, as previously described, for the purpose of the present invention. Also, conventional cigarette filter rodmaking and cigarette making and filter tipping apparatus may be used in the present invention whereby the filter is first formed as a continuous rod, then cut into six-filter lengths, subsequently cut into two-filter lengths, each two-filter length is wrapped in cigarette wrapper paper with a column of tobacco at each end and each of the thus formed two-cigarette products is cut at its middle, i.e., through the middle of the filter which joins the two tobacco columns, each of said products thereby yielding two filter tip cigarettes. In the present invention there may be used a cellulose acetate tow of lower denier than conventional cellulose acetate cigarette filter tow because the tow is supplemented by the cellulosic web.

The drawings, in detail, are described as follows:

In FIG. 1, cellulose acetate tow 12 is fed to the nip of metering rolls 11 and 11' and from said nip to trumpet 15 leading to the garniture (not illustrated) of a conventional cigarette filter rodmaker (not illustrated). Simultaneously, tissue paper 13 is metered from roll 14 into trumpet 15. Since tow 12 and tissue paper 13 are fed on top of each other, neither tow 12 nor paper 13 being bundled and directed to the center of the other, the resultant rod is the aforesaid double-helicoid embodiment. In ghost form there is illustrated funnel 16. If such funnel is used to gather tissue paper 13 into a bundle and direct it into the center of tow 12, the resultant rod is an aforesaid sheath/core embodiment. The arrow indicates the direction of movement of paper 13 and tow 12.

In FIG. 2, there is illustrated a sheath/core embodiment. Darkened portion 22 is the tissue paper (colored paper being used for illustrative purposes) and surrounding portion 21 is cellulose acetate. Such results are attained when funnel 16 is used with trumpet 15 in the FIG. 1 embodiment.

The present invention is further described by reference to the following example:

EXAMPLE A hollow fil, 3.0 denier per fil, 26,200 total denier conventionally crimped cellulose acetate cigarette filter tow is opened in a profiled roll unit comprising two sets of paired rubber surfaced and threaded rolls, as described in US. Patent No. 3,032,829 and is then plasticized with glycerol triacetate in a centrifugal plasticizer applicator as described in commonly assigned US. patent application Ser. No. 216,894, filed Aug. 14, 1962; said tow, directed by a conventional trumpet, is then fed to the garniture of a conventional cigarette filter rodmaker; simultaneously, to the center of the lower surface of said tow is directed a web of colored tissue paper fed from a roll of toilet tissue, said web being directed by a truncated conical funnel inserted partially into the mouth of said trumpet and having an exit opening substantially smaller than the width of the web and of the tow whereby the web is transversely bunched to a width substantially smaller than the tow width; said tow and said bunched web are passed through the garniture wherein said tow and said web are condensed (i.e., compressed) together into a continuous rod, therein the web comprising a core and the tow comprising a sheath about said core. The continuous rod is cut into 6-filter tip lengths of 102 mm. by the rodmaker and is subsequently cut into 17 mm. single filter tip lengths. The colored paper shows that the paper web constitutes the core of the filter rods and tips. The properties of rod and tip are tabulated as follows:

Rod properties:

Length 102mm. Circumference 24.9 mm. Weight 0.889 g. Acetate 0.378 g. Paper 0.391 g. Plasticizer (glycerol triacetate triacetin) 0.050 g. compressibility 20%. Pressure drop 186 mm. of H 0. Tip properties:

Length 17 mm. Pressure drop 36 mm. of H 0. Efficiency 42.4%. Particulate delivery 27.8 mg./cigarette.

The tip pressure drop is exceptionally low. Identical length and circumference tips made individually of 3.2 and 4.0 denier per fil hollow fil and 3.9 and 4.7 denier per fil ordinary fil cellulose acetate filter tow would be found to have a smoke removal efiiciency of about 38.0% for the rods made from the hollow fil tows and about 36.9% for the rods made from the ordinary fil tows (denier per fil not being a significant parameter) when of the same rod pressure drop as the rod of the present example. The smoke removal efficiency (efiiciency) of the rod made by the present invention is indeed substantially higher, being 42.4%. It is thus seen that, since an arithmetic plot of AP v. SRE is essentially linear, at higher tip pressure drops, such as a commercially common 90 mm. of H 0 pressure drop, smoke removal efficiencies would be well up into the %-plus or %-plus range or even higher.

With regard to the rod weight, it is to be noted that the total weight of acetate (i.e., cellulose acetate), paper (i.e., the cellulosic filter material) and plasticizer is 0.819 gram. The difference between this weight and the total rod weight is 0.070 gram. This difference is accounted for by the fact that with a conventional cigarette filter rodmaker, as in the present example, there is used a glue line applicator and filter wrapper attachment. The filter wrapper attachment comprises means for feeding a continuous strip of paper to the garniture, to which strip, before it reaches the garniture, there is applied a continuous line of glue by the glue line applicator. In the garniture, the paper strip is wrapped about the filter in a single layer except for a slight overlap at which the resultant wrapper is sealed by another application of glue. The aforesaid 0.070 gram weight difference is the weight of the filter wrapper and glue. The filter wrapper is conventionally used to help maintain the integrity of the filter material in subsequent machine handling and in smoking by the consumer. The glue line application is a precaution by which the filter material is cohered to the wrapper at least along said line thereby avoiding any possibility that the filter material will slip out of the wrapper.

It is to be understood that the above description is merely illustrative of the scope of the present invention "and that many variations within the spirit of the invention may be obvious to the average worker in the art.

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

1. In a method of making tobacco smoke filters, the improvement which comprises bringing together two webs, one of said webs comprising a multiplicity of continuous synthetic filaments, condensing said webs together thereby shaping them into a Single continuous rod having an effective filtration cross section comprising elements of each of the webs, and dividing said continuous rod into a plurality of discrete lengths, said discrete lengths comprising said tobacco smoke filters.

2. The method defined in claim 1, wherein to at least one of said two webs is applied a selective filtering agent.

3. The method of claim 1, wherein one of said two webs is cellulose acetate tow and the other of said two webs comprises a cellulosic.

4. The method defined in claim 3, wherein said cellulosic is paper.

5. In a method of making tobacco smoke filters, the improvement which comprises feeding to the garniture of a cigarette filter rodmaker a first web of filter material and simultaneously feeding through a truncated conical funnel guide and then into said garniture a second web of filter material one of said webs comprising a multiplicity of continuous synthetic filaments, said funnel guide being directed toward the center of said first web and having an exit diameter substantially smaller than the width of said second web, said funnel guide thereby gathering said second web into a bundle and directing it to the center .of said first web, condensing said webs in said garniture whereby said first web is condensed about said bundled second web thereby forming a single continuous rod wherein the second web comprises a core and the first web comprises a sheath about said core, said rod having an effective filtration cross section comprising elements of each of the webs, and dividing said continuous rod into a plurality of discrete lengths, said discrete lengths comprising said tobacco smoke filters.

6. The method defined in claim 5, wherein said first web is cellulose acetate tow and said second web comprises a cellulosic.

7. The method defined in claim 6, wherein said cellulosic is paper.

8. In a method of making filter rods wherein an elongate web of a multiplicity of continuous synthetic filaments is fed continuously to the garniture of a cigarette filter rodmaker and condensed into a single continuous rod, the improvement which comprises feeding to said garniture with said synthetic filament band a continuous cellulosic web condensing said webs together in said garniture in a cross-sectional configuration whereby said cellulosic web constitutes a portion of the effective filtration cross-section, said cellulosic web comprising at least 10 percent by weight of said web materials.

9. The method of claim 8, wherein said cellulosic web comprises at least 30 percent by weight of said web materials, and is disposed interiorly of said synthetic filament web.

10. The method of claim 8, wherein said synthetic filaments are cellulose acetate, said cellulose web and said cellulose acetate web each comprise equal weight proportions of said filter rods, said webs are interfacially cohered, and are disposed in the configuration of concentric helicoids in face-to-face relationship.

11. The method defined in claim 8 wherein said web 7 and said tow are fed as an interfacially cohered composite web.

12. The method defined in claim 8 wherein said cellulosic web is paper.

13. The method defined in claim 12 wherein adhesive is applied at the prospective interface of said paper and said tow whereby during said subsequent condensing said paper and said tow become cohered at their interface.

References Cited UNITED STATES PATENTS 2,900,988 8/1959 Crawford et a1 161 8 Wade 131267 Schur et a1. 161 Cobb 161 Parmele 161 Schaaf 131267 Muller 156-462 Gallagher 156-178 Gallagher 156180 10 EARL M. BERGERT, Primary Examiner.

D. I. FRITSCH, Assistant Examiner.

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