RU2357624C2 - Tobacco smoke filter - Google Patents

Abstract

FIELD: tobacco industry.

SUBSTANCE: proposed tobacco smoke filter contains high-performance absorbent carbon impregnated with a metallic saturant.

EFFECT: utilisation of a relatively low-grade saturant in combination with the basic carbon material characterised by enhanced performance as compared to agents habitually used in cigarette filters provides for improved efficiency of HCN removal from tobacco smoke.

16 cl, 3 dwg, 7 tbl, 2 ex

Description

This invention relates to tobacco smoke filters, in particular for cigarettes.

It is well known to use activated carbon to remove unwanted vapor phase (PF) components from tobacco smoke.

The PF fraction of cigarette smoke contains more than 400 compounds (for example, aldehydes, ketones and hydrocarbons). Activated carbon is a strong adsorbent; it is effective in removing a large number of these compounds from tobacco smoke. However, since there is a tendency to a certain decrease in the content of all compounds in the PF fraction with activated carbon, then activated carbon can be considered as an effective “common adsorbent”.

In recent years, there has been a growing interest in selective filtering using cigarette filters, that is, in enhanced removal of individual compounds from tobacco smoke compared to the removal of other smoke components. One of the compounds for which selective removal is particularly desirable is hydrogen cyanide (HCN), since HCN is usually considered one of the most toxic compounds found in the PF fraction. HCN is removed with standard activated carbon used in cigarette filters, but it does not selectively remove it compared to other PF compounds. In reality, its removal is usually lower than for the other PF compounds.

It is well known that various chemicals are added to activated carbon to enhance the removal of certain compounds. These "enriched coals" are capable of removing certain compounds both through chemical reactions and through physical adsorption. Such coals are widely used, for example, in gas masks and respirators, where activated carbon is usually enriched with one or more chemicals to ensure the removal of certain toxic substances. Our experiments have shown that such a respiratory-type coal is relatively ineffective when used with cigarette filters because only low levels of total removal are achieved. It is clear that these coals of a respiratory type are not suitable for a cigarette filter, where the duration of contact of coal with gas is much shorter than if they were used in gas masks / respirators. In addition, these respiratory-type coals show little evidence of increased selectivity for HCN. The foregoing leads to the assumption that in order to effectively remove the HCN compound in the cigarette filter, a large amount of impregnation will be required.

Unexpectedly for ourselves, we found that when removing HCN from cigarette smoke, it is highly effective to use a relatively low level of impregnating substance in combination with base coal, which has a higher activity compared to coal used in standard cigarette filters.

In accordance with this invention, there is provided a tobacco smoke filter comprising high activity activated carbon enriched in a metal impregnating substance.

Preferably, if the metal impregnating substance is present in amounts that comprise up to 10% of the dry weight of activated carbon of high activity. More preferably, if the impregnating substance is present in amounts that comprise from 1 to 5% of activated carbon of high activity. The metallic impregnating agent may be, for example, at least one of the following elements: copper, manganese, molybdenum, cobalt, iron, zinc. In one preferred embodiment, the impregnating agent is copper. In another preferred embodiment, the metal impregnating agent is a combination of copper and molybdenum.

In this description, under the terms "metal impregnating substance", "copper", "molybdenum", etc. the metals themselves and / or their ions in any form (for example, salts, complex compounds, chelates, etc.) are meant.

The activated carbon used in the invention can be obtained from any raw material for which activated carbon can be prepared (this raw material from which activated carbon can be prepared includes, for example, wood, coal, nutshells such as coconut, peat, petroleum coke and bone, as well as synthetic sources such as poly (acrylonitrile) or phenol formaldehyde.

Activated carbon is "high activity" activated carbon. In this case, “activity” refers to the percentage by weight of a specific vapor (eg, carbon tetrachloride) adsorbed under equilibrium with basic activated carbon (the term “basic activated carbon” refers to activated carbon before being enriched in an impregnating substance, such as copper and / or molybdenum). Activity levels are given as percentages for carbon tetrachloride. Thus, the numerical value of carbon activity at 95% for carbon tetrachloride refers to the adsorption level of carbon tetrachloride at 95% by weight at equilibrium. “High activity” refers to basic activated carbon (that is, activated carbon prior to metal enrichment) that adsorbs more than about 90% of carbon tetrachloride under equilibrium. Preferably, the activity before impregnation is more than 90%. More preferably, the activity of the activated carbon prior to impregnation is more than 100% (i.e., the main activated carbon adsorbs more than about 100% of carbon tetrachloride under equilibrium).

It is preferable if the activated carbon after impregnation has an activity exceeding 80% for carbon tetrachloride, more preferably more than 90% for carbon tetrachloride.

In accordance with a further aspect of the present invention, there is provided a tobacco smoke filter comprising activated carbon that is enriched in copper and molybdenum in a ratio of greater than 1.3 to 1.

The preferred ratio of copper to molybdenum (by weight) in enriched activated carbon is greater than 2: 1. Particularly preferred ratios are from 3.5: 1 to 4.5: 1. A particularly preferred ratio of copper to molybdenum in enriched activated carbon is 4: 1.

Preferably, the activated carbon is high activity activated carbon.

In accordance with a further aspect of the present invention, there is provided a tobacco smoke filter comprising activated carbon that is enriched in copper and molybdenum, the activated carbon being a high activity activated carbon.

Activated carbons of high activity are discussed above. It is preferable if the activity of activated carbon exceeds 90% in carbon tetrachloride, more preferably if it exceeds 100% in carbon tetrachloride.

Preferably, copper and molybdenum are present together in an amount not exceeding 10% of the dry weight of activated carbon. Preferably, if copper and molybdenum are present in activated carbon in an amount that is from 1 to 5% of the dry weight of activated carbon.

Preferably, the ratio of copper to molybdenum exceeds 1.3 to 1. More preferably, the ratio of copper to molybdenum exceeds 2 to 1, more preferably from 3.5 to 1 to 4.5 to 1. A particularly preferred ratio of copper to molybdenum is 4. to 1.

Quite unexpectedly, we found that a significant decrease in the concentration of metallic impregnating substance (e.g., the concentration of copper / molybdenum impregnating agent) compared to the concentration of impregnating substances commonly used in military or civilian respirators does not lead to a noticeable deterioration in HCN removal.

The particle size of the activated carbon according to this invention depends on the required characteristics and configuration of the filter. The mesh sizes given in the description are "US mesh" (number of holes or cells per linear inch). Enriched activated carbon with a particle size of 2 mm (10 mesh) to 0.15 mm (100 mesh) is suitable. More preferably, if substantially all of the enriched activated carbon has a particle size of from 0.6 mm (30 mesh) to 0.212 mm (70 mesh). More preferably, the entire enriched activated carbon has a particle size of from 0.425 mm (40 mesh) to 0.212 mm (70 mesh).

Enriched activated carbon tobacco smoke filters according to this invention can exhibit surprising selective removal of HCN without undesirable effects on the overall reduction in PF. Previously, enriched coal was not preferred when used in cigarettes because chemical reactions between the enriched component (for example, a metal ion) and substances present in the smoke (and / or products of these reactions) have an undesirable effect on the taste of the cigarettes, which reduces the pleasure, received by smokers. The tobacco smoke filters of this invention may contain substantially smaller amounts of, for example, saturated copper, saturated copper and molybdenum than previously thought necessary for the acceptable removal of HCN, it seems that this reduces any adverse effects on taste.

In addition, the applicants have shown that the benefits of activated carbon in the filters of this invention are surprisingly effective at lower activated carbon weights. This can reduce the costs associated with filter manufacturing. Preferred tobacco smoke filters contain less than 150 mg of activated carbon enriched in metal impregnating agents (e.g., copper and molybdenum). The most preferred tobacco smoke filters contain from 10 mg to 70 mg of enriched activated carbon, more preferred from 30 mg to 60 mg of enriched activated carbon.

The filter of this invention may be of any design previously proposed for tobacco smoke filters containing particulate absorbent. For example, the enriched activated carbon of the present invention can be dispersed throughout the filter insert and located on a tow, fiber or sheet material that is assembled to form a filter insert; in another embodiment, it can be glued to one or more threads that pass through the grill of the filter insert, or glued to the inner surface of the wrapper around the filter insert (as described, for example, in GB-A-9124535 and GB-A-9221545, referred to attention for more information); or it can form a base inserted between a pair of inserts (for example, from a bundle of cellulose acetate) in a common wrapper.

The filters of this invention may further comprise at least one particular adsorbent that is different from activated carbon required by the invention (for example, silica gel, another activated carbon or zeolite), and which is able or not able to selectively remove other compounds present in the fraction PF cigarette smoke (e.g. aldehydes). Additional adsorbent (additional adsorbents) can be mixed with activated carbon, mandatory according to this invention, and / or separated from it.

The tobacco smoke filters of this invention can also provide effective removal of HCN even after extended periods of time (for example, during storage) after the manufacture of filters or cigarettes. The carbon used in known filters adsorbs the volatiles present in the filter or tobacco during storage, thereby reducing the efficiency with which the filter carbon can remove PF compounds while smoking a cigarette. Because of this, the efficiency with which known filters remove HCN also decreases with aging. Surprisingly, with the filters of this invention, the ability to remove HCN does not decrease significantly even after storage for extended periods of time (e.g., six months).

The present invention also provides a filter cigarette, comprising a filter according to any preceding claim, connected at its upstream end to a wrapped tobacco rod. The cigarette filter of the present invention is usually attached to the wrapped tobacco rod with a conventional, glued outer wrap, which may be a ventilated or non-ventilated lap joint.

The invention is illustrated by the following examples with reference to the accompanying drawings, in which FIGS. 1 and 2 are respectively not scaled-out schematic side sections of an individual filter and filter cigarette according to one embodiment of the invention, and FIG. 3 is a not shown scaled side schematic section of a separate filter assembly according to another embodiment of the invention.

Comparative Examples - Coals for Respirators

Enriched commercial coals recommended for HCN removal for respirators were obtained in large quantities from several suppliers and compared with standard (unenriched) charcoal commonly used in cigarette filters. These tests included assembling cigarettes with triple grain filters, each containing 100 mg of activated carbon in a layer packed between two segments of a cellulose acetate filter. The filter cigarettes were smoked according to ISO conditions (puffs with a volume of 35 cm ³ , each of which had a duration of two seconds and was performed once a minute), and the resulting hydrogen cyanide HCN and the average value of the resulting PF were measured. The percentage reduction in the average PF and HCN for cigarettes from A to F (each of which contains one of six typical activated carbons for respirators) compared to an equivalent cigarette that does not contain carbon in the filter is shown in Table 1. The table also includes the values of PF and HCN for a “standard” cigarette containing a filter that includes unenriched activated carbon (commonly used in cigarette filters) derived from coconut shells.

Table 1 Reference sample The decrease in the average PF (%) HCN reduction (%) Standard 55 44 BUT 22 23 AT 27 31 FROM 25 41 D 29th 47 E 23 46 F 39 36

It can be seen that samples A to F intended for respirators are not suitable for the working conditions of cigarette filters. It is also seen that the standard filter is not selective for HCN.

Preparation of Enriched Samples

Enriched activated carbon samples were prepared in the usual way by dissolving basic copper (II) carbonate, ammonium carbonate and ammonium dimolybdate in aqueous ammonia solution and mixing with activated carbon in accordance with the ratios given in table 2 (shown for 2% copper; 0.5% molybdenum). Quantities for other metal concentrations (and ratios) were set appropriately. The resulting suspension was heated to 175 ° C to obtain a dry free flowing product, which was then sieved to obtain the desired size.

table 2 Components Weight (g) Activated carbon 1000 basic copper (II) carbonate 44 ammonium dimolybdate (VI) 12 ammonium carbonate twenty water 460 ammonium solution (0.88) 158

Enriched Sample Tests

Fourteen samples of enriched activated carbon were prepared by the method described above. Filter cigarettes were collected, each containing 100 mg of one of the samples, and tested using the above procedure described for the above comparative samples. The results for fourteen enriched samples and for two unenriched control (samples with numbers 3 and 4) are shown in table 3.

An additional sample of enriched coal, containing 2% copper only, was prepared using the procedure described above, except that there was no ammonium dimolybdate in the mixture. This sample (its number 27) was tested using the same procedure that was used for the samples included in table 3, and the results are presented in table 3a.

Table 3 Sample Number Carbon activity (% by CHC) Carbon activity (% by CHC) Enriched Metal Content (%) * Sieve Size (US Mesh) The decrease in the average value of the PF (%) HCN reduction (%) one 80 46 > 10 20/40 29th 46 2 80 47 > 10 12/20 fifteen 25 3 95 on zero 30/70 77 75 four 60 on zero 30/70 51 53 5 101 75 10 30/70 42 92 6 122 82 10 30/70 66 93 7 101 84 5 30/70 56 92 8 103 91 5 30/70 64 83 9 80 73 5 30/70 69 93 10 83 75 5 30/70 46 58 eleven 101 91 2.5 30/70 81 88 12 101 95 1.25 30/70 83 88 13 101 91 2.5 30/70 77 82 fourteen 108 99 2.5 12/20 57 70 fifteen 125 111 2.5 30/70 90 91 16 125 111 2.5 12/20 65 74 * Presented for (copper + molybdenum) in a 4: 1 ratio. Table 3a Sample Number Carbon activity (% by CHC) Carbon activity (% by CHC) Enriched Metal Content (%) (Copper) Sieve Size (US Mesh) The decrease in the average value of the PF (%) HCN reduction (%) 27 one hundred 95 2.0 30.40 80 82

The results show that in order to achieve a significant reduction in the PF substance (i.e., a decrease in the components in the PF fraction of cigarette smoke) simultaneously with a significant reduction in HCN (a decrease in HCN in the PF fraction of cigarette smoke) in cigarette filters, which are embodiments of the present invention, such as samples with Numbers 11, 15 and 27, it is desirable to use high activity base coal (more than about 90% carbon tetrachloride) in combination with a relatively low level of metal enrichment (less than 10%, p edpochtitelney from 1 to 5%).

Higher activity on ChC lead to the fact that there are higher ability to retain HCN and PF. PF delay increases with decreasing concentration of the impregnating substance. The delay in HCN remains almost constant when measured as a function of the concentration of copper and molybdenum (Table 3). Therefore, it is surprising that a significant decrease in the concentration of copper / molybdenum impregnating agent compared to those used in civilian or military respirators results in an indistinguishable deterioration in the removal of HCN by filters containing these coals.

Activated carbons were prepared from various basic materials (for example, coconut shells and coal); it was found that there is a slight difference in HCN delay between, for example, charcoal and coconut for the same sieve sizes, levels of impregnation and activity.

It can also be clearly seen from the results that smaller cell sizes (for example, a 30/70 mesh US mesh size) give HCN characteristics superior to those obtained with larger cells (compare, for example, samples 15 and 16). This contradicts the commonly observed behavior of cigarette filters, in which it was found that a change in cell size has only a relatively small effect on PF removal.

Our experiments also showed that the relative advantages of activated carbon in embodiments of the invention are even more pronounced at lower levels of carbon weight in the filter. Samples numbered 8 and 11 were used in the manufacture of cigarette filters having two different coal weights (for example, metal levels of 5% and 2.5%, respectively, and tested as described above. The results are presented in tables 4a and 4b.

Table 4a cigarette filter, including sample No. 8. Coal Weight (mg / sig.) The average decrease in PF (%) The average decrease in HCN (%) 95 76 87 fifty 40 80 Table 4b cigarette filter, including sample No. 11. Coal Weight (mg / sig.) The average decrease in PF (%) The average decrease in HCN (%) 95 72 90 fifty 56 80

Preservation of characteristics for a long time

A disadvantage of known filters containing coal is that during storage, coal in the filter adsorbs volatile substances present in the filter or in tobacco, thereby reducing the efficiency with which coal can remove PF compounds when smoked. This is manifested in the fact that with aging, the overall efficiency with which known carbons remove HCN decreases. Applicants have studied the changing characteristics of filter cigarettes containing filters of this invention. Each filter contained approximately 95 mg of coal.

Filters that implement this invention were stored in the form of collected cigarettes, and changes in their characteristics were measured after 0, 3 and 6 months. The results are shown in table 5.

Table 5 Exposure months Standard coal *. Average decrease Sample No. 8. Average decrease Sample No. 11. Average decrease PF (%) HCN (%) PF (%) HCN (%) PF (%) HCN (%) 0 64 53 76 87 72 90 3 55 41 62 86 63 88 6 45 29th 48 85 fifty 85 * Coal, the test results of which are shown in table 1.

It can be seen that the characteristic of HCN reduction in the filters implementing this invention, which are manufactured with samples 8 and 11, after six months did not decrease significantly (especially in comparison with a sample containing standard coal).

1 and 2 are, respectively, not shown to scale schematic side sections of an individual filter and filter cigarette according to one embodiment of the invention.

The filter shown in FIG. 1 comprises a cylindrical filter insert 2 from an acetate cellulose tow, located at the mouth-facing end, a cylindrical filter insert 3 from an acetate cellulose tow, located upstream, and a filter wrapper 4 wrapped around the inserts to form between them cavity 6. The cavity 6 is filled with granules 17 of activated carbon enriched in copper and molybdenum, prepared in accordance with the methods described above and having a composition identical to the composition of the sample at number 11, o written above.

FIG. 2 shows a filter belonging to the type of filters shown in FIG. 1 and connected by its upstream end 7 to a tobacco rod 10 in its own wrapper 11 using a fully adhesive outer wrapper 12 which surrounds and attaches the entire length of the filter and only the adjacent end of the wrapped tobacco rod 10, 11.

Example 17

In a specific example of a filter and a filter cigarette made according to this invention and described with reference to FIGS. 1 and 2, the filter has a length of 27 mm and a circumference of about 25 mm. The insert 2, located at the end facing the mouth, is a non-wrapped acetate insert 10 mm long, i.e. a preformed non-wrapped insert of plasticized cellulose acetate fibers assembled and joined together as is well known in the art.

Insert 3, located on the upstream end, is a wrapped acetate insert 10 mm long,

those. a preformed wrapped insert of plasticized cellulose acetate fibers. The filter wrapper has a length of 27 mm and forms a cavity 6, which has a length of 7 mm and is located between inserts 2 and 3. The cavity 6 is filled with 100 mg of granules 17 of activated carbon enriched with copper and molybdenum, prepared in accordance with the methods described above, and having the composition is identical to the sample with the number 11 described above. The filter rod is attached to the commercial wrapper of the tobacco rod 10, 11 by means of a breathable adhesive outer wrap 12.

In yet another specific example (Example 17a), cavity 6 is filled with 100 mg of copper-rich activated carbon granules 17 prepared in accordance with the methods described above and having a composition identical to the sample number 27 described above.

It should be borne in mind that example 17 and example 17A are similar in design to the well-known triple granular filter, but contain activated carbon, corresponding to this invention.

Figure 3 is a schematic side sectional view of a separate filter in another embodiment of the invention, not shown to scale.

The filter of FIG. 3 has a cylindrical insert 52 from a cellulose acetate tow, located at the mouth-facing end, and a cylindrical filter insert 53, also made from a cellulose acetate tow and located upstream. Particles 67 of activated carbon enriched in copper and molybdenum, prepared in accordance with the methods described above, and identical in composition to sample numbered 11, described above, are distributed throughout the upstream filter insert 53 and are located on a bundle, or fibers, or sheet material that is assembled to form an insert. A filter wrap 54 is wrapped around the inserts. It is understood that the filter of the type shown in FIG. 3 can be attached with its upstream end 57 to the tobacco rod as shown in FIG. 2 with reference to Example 17, for example attached to the tobacco rod in its own wrapper with a fully glued outer wrapper that surrounds and connects the entire length of the filter and only the adjacent end of the wrapped tobacco rod.

Example 18

In a specific example of a filter made in accordance with this invention and described with reference to FIG. 3, the filter has a length of 27 mm and a circumference of about 25 mm. The insert 52, located at the mouth-facing end, is a non-wrapped acetate insert of 14 mm length, i.e. a preformed non-wrapped insert of plasticized cellulose acetate fibers assembled and bonded together as is well known in the art.

The insert 53, located at the upstream end, is also a 13 mm long preformed insert from plasticized cellulose acetate fibers assembled and knitted together as is well known in the art. 50 mg of particles 67 of activated carbon enriched in copper and molybdenum, prepared in accordance with the methods described above, and identical in composition to sample number 11 described above, are distributed throughout the filter insert 53 and are located on the material of the bundle (fiber) that is assembled with the formation of the insert. The methods by which particles can be incorporated into the tow material during assembly are well known in the art. The filter wrapper 54 is wrapped around the inserts and has a length of 27 mm.

The filter rod may be glued to a commercial tobacco rod wrapper with a breathable wrapper as shown in FIG. 2 and described with reference to this drawing.

In an additional specific example (example 18a), the cavity is filled with 50 mg of copper-enriched activated carbon particles 67 prepared in accordance with the methods described above and identical in composition to sample number 27 described above, distributed throughout the filter insert 53 and located on harness material.

It should be borne in mind that examples 18 and 18a are similar in design to the known active acetate filter, but contain activated carbon according to this invention.

It should be borne in mind that the filter according to this invention can have any design previously proposed for tobacco smoke filters with particulate adsorbent when replacing the known particulate adsorbent with enriched activated carbon according to this invention.

Claims (16)

1. A tobacco smoke filter containing activated carbon enriched with a metal impregnating substance, in which the activated carbon is high activity activated carbon. 2. The tobacco smoke filter according to claim 1, in which the metal impregnating substance is at least one of the following substances: copper, molybdenum, manganese, cobalt, zinc and iron. 3. The tobacco smoke filter according to claim 1 or 2, in which the metal impregnating substance (substances) is present in an amount not exceeding 10% of the dry weight of activated carbon of high activity. 4. The filter according to claim 3, in which the metal impregnating substance (s) is present in an amount of 1 to 5% of the dry weight of activated carbon. 5. The tobacco smoke filter according to claim 3, in which the metal impregnating substance is copper. 6. A tobacco smoke filter containing activated carbon that is enriched in copper and molybdenum, the ratio of copper to molybdenum exceeding 1.3 to 1. 7. A tobacco smoke filter containing activated carbon that is enriched in copper and molybdenum, the activated carbon being a high activity activated carbon. 8. The filter according to any one of claims 1, 6 and 7, in which, before enrichment, activated carbon has an activity exceeding 90% of the activity for carbon tetrachloride. 9. The filter of claim 8, in which the activated carbon prior to enrichment has an activity exceeding 100% activity for carbon tetrachloride. 10. The filter of claim 8, in which the activated carbon after enrichment has an activity exceeding 80% of the activity for carbon tetrachloride. 11. The filter of claim 8, in which the activated carbon after enrichment has an activity exceeding 90% of the activity for carbon tetrachloride. 12. The filter of claim 8, in which essentially all of the activated carbon is a particle size of from 2 to 0.15 mm, more preferably from 0.6 to 0.212 mm. 13. The filter of claim 8, which contains from 10 to 150 mg of activated carbon, preferably from 30 to 60 mg of activated carbon. 14. The filter of claim 8, which contains at least one additional adsorbent. 15. The filter of claim 14, wherein the additional adsorbent (adsorbents) selectively removes a compound (s) other than HCN present in the PF fraction of the cigarette smoke. 16. A filter cigarette containing a filter according to any one of the preceding claims, attached at its upstream end to a wrapped tobacco rod.

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