DE102024121792A1 - FILTER MATERIAL WITH REDUCED MIGRATION OF ADDITIVES - Google Patents

Abstract

A filter material is shown comprising a cellulose fiber-based substrate, an additive and an adhesion promoter, wherein the mass ratio of the additive and the adhesion promoter is at least 1:3 and at most 2:1, and the additive and the adhesion promoter together constitute at least 3% and at most 40% of the mass of the cellulose fiber-based substrate, wherein the additive is triethyl citrate, triacetin or a mixture of these substances, and wherein the adhesion promoter is selected from the group consisting of ethanediol, propanediol, butanediol, pentanediol and glycerin diacetate or mixtures thereof.

Description

AREA OF INVENTION

The invention relates to a cellulose fiber-based filter material for smoking products, comprising an additive and an adhesion promoter, wherein the adhesion promoter improves the adsorption of the additive to the cellulose fibers and thus significantly reduces the migration of the additive.

BACKGROUND AND STATE OF THE ART

Smoking articles are typically rod-shaped articles containing an aerosol-forming material and at least one segment designed to influence the properties of the aerosol.

The smoking product in question may be a filter cigarette, in which a first segment contains the aerosol-generating material, in particular tobacco, and a further segment, designed as a filter, serves to filter the aerosol. The aerosol is generated by burning the aerosol-generating material, and the filter primarily serves to filter the aerosol and to provide the filter cigarette with a defined draw resistance.

The smoking product may also be a so-called tobacco heater, in which the aerosol-generating material is heated but not burned. This reduces the number and quantity of harmful substances in the aerosol. Such a smoking product also consists of at least two, but more often of four or five segments. One segment contains the aerosol-generating material, which typically includes tobacco, reconstituted tobacco, tobacco processed by other methods, or nicotine and glycerol or propylene glycol. Further, sometimes optional, segments in the tobacco heater serve to direct the aerosol, cool it, or filter it.

The smoking product may also be an electronic cigarette or a vaporizing device that contains an aerosol-forming material, typically in the form of a liquid or gel, in a reservoir, and furthermore includes a segment that serves at least partially to filter the aerosol.

The segments are usually encased in a covering material. Paper is very often used as this covering material.

It is known from the prior art to produce such segments from cellulose acetate or polylactides. Since polylactides, and especially cellulose acetate, biodegrade very slowly in the environment, the industry has an interest in manufacturing the segments of smoking products from other materials that are more readily biodegradable and, above all, allow for the elimination of the use of cellulose acetate. It is known in the prior art to produce segments for smoking products, especially filter segments, from cellulose fibers. While such segments are generally readily biodegradable, they also have disadvantages. For example, segments made of cellulose fibers generally have a high filtration efficiency and therefore result in a dry aerosol, which impairs the taste of the aerosol compared to cigarettes with the usual cellulose acetate segments. Furthermore, they often have a lower filtration efficiency for phenols than cellulose acetate. Furthermore, it proves difficult to produce a segment from cellulose fibers that is acceptable to consumers in terms of the combination of tensile strength, filtration efficiency, and hardness. To reduce filtration efficiency, fewer cellulose fibers are often used per filter volume, which, however, results in a softer segment with low tensile strength.

To adapt the filtration efficiency and other properties of cellulose fiber segments to those of cellulose acetate segments, various additives can be used. EP 2 515 689 For example, a filter element is described which comprises a filter paper and triethyl citrate, triacetin or polyethylene glycol to increase the filtration efficiency for semi-volatile substances such as phenols, with the suggestion that triethyl citrate, triacetin or polyethylene glycol can make up to 30% of the mass of the filter element.

While triethyl citrate and triacetin have proven generally suitable for increasing the filtration efficiency of semi-volatile substances such as phenols in filter paper, their reliable filtration performance is lacking in practical applications. Therefore, there is an industrial interest in having a biodegradable filter material available that can also ensure high filtration efficiency for semi-volatile substances in practical applications.

SUMMARY OF THE INVENTION

The invention is based on the objective of providing a filter material with which the filtration efficiency of the segment of a smoking product made from this filter material can be adjusted to meet the requirements of the user. segments made of cellulose acetate can be reliably adapted under practical conditions.

This problem is solved by a filter material according to claim 1, a segment of a smoking article according to claim 26, and a smoking article according to claim 37. Advantageous embodiments are specified in the dependent claims.

The inventors have found that this problem is solved by a filter material comprising a cellulose fiber-based substrate, an additive, and an adhesion promoter, wherein the mass ratio of the additive and the adhesion promoter is at least 1:3 and at most 2:1, and the additive and the adhesion promoter together constitute at least 3% and at most 40% of the mass of the cellulose fiber-based substrate. According to the invention, the additive is triethyl citrate, triacetin, or a mixture of these substances, and the adhesion promoter is selected from the group consisting of ethanediol, propanediol, butanediol, pentanediol, and glycerin diacetate, or mixtures thereof.

As additives in the filter material according to the invention, triethyl citrate and triacetin offer the advantage of increasing the filtration efficiency for phenols, thus making the filtration properties more similar to those of cellulose acetate. These desired filtration properties can be reliably demonstrated in laboratory test products, but prove less reliable in practical applications. The inventors have identified the reason for this unsatisfactory behavior in practice as the tendency of these additives to migrate out of the filter material. In practice, months regularly elapse between the manufacture and use of a smoking product, and during such a long period, a considerable proportion of the additives can migrate out of the filter material and thus no longer contribute to increasing the filtration efficiency for semi-volatile substances. This could, in principle, be counteracted by using larger quantities of additives from the outset to prevent loss through migration. However, this is not an optimal solution for several reasons. Firstly, it increases the consumption of additives. On the other hand, the migration of additives is undesirable in itself, and this negative effect is exacerbated by an already higher initial concentration of additives. For example, additives from the filter material can migrate into the surrounding wrapping paper, creating visible stains that detract from the appearance of the smoking product. This problem becomes more pronounced the higher the concentration of additives in the filter material. The additives can also migrate into the aerosol-generating material and be converted into components of the aerosol during use, which is undesirable not only for its impact on taste but also for toxicological reasons.

According to the inventors, the aforementioned additives tend to migrate because they are nonpolar molecules that are not well adsorbed onto the cellulose fibers of the filter material. However, this adsorption capacity can be significantly improved by the adhesion promoters according to the invention. These adhesion promoters possess both polar groups, which allow them to be readily adsorbed onto the cellulose fibers, and nonpolar groups, which enable them to adsorb the additive and thus considerably reduce its migration. This ensures that the improved filtration efficiency is maintained even after several months of storage. Furthermore, the formation of stains in the packaging material is prevented, and other components of the smoking product are not contaminated by the additive.

The inventors have determined that the additive and the adhesion promoter must be present in the filter material in a specific ratio so that the number of apolar groups of the adhesion promoter matches, at least approximately, those of the additive.

The cellulose fiber-based substrate comprises cellulose fibers, wherein preferably at least 70%, more preferably at least 90%, and most preferably at least 99% of the mass of the cellulose fiber-based substrate are formed by cellulose fibers. Preferably, the cellulose fibers are pulp fibers, fibers of regenerated cellulose, or a mixture thereof.

Particularly preferred are cellulose fibers obtained from coniferous trees, deciduous trees, or other plants such as hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, bamboo, cotton, or esparto grass, or a mixture of cellulose fibers from two or more of these trees or plants. In other words, the cellulose fibers can be obtained from exactly one of the sources mentioned above, or be a mixture of cellulose fibers obtained from two or more of the aforementioned sources. Particularly preferred are cellulose fibers obtained from hemp, flax, jute, coconut, abaca, sisal, or cotton, or a mixture of cellulose fibers from two or more of these plants.

The cellulose fibers can be bleached or unbleached and can be used in any mixture of bleached and unbleached cellulose fibers, for example in a mixture of bleached and unbleached cellulose fibers in a mass ratio of 100:0, 20:80, 50:50, 80:20 or 0:100. Apart from the brownish color, the unbleached cellulose fibers have no special effect, but can offer ecological advantages because the bleaching process can be omitted.

Particularly preferred are fibers of regenerated cellulose spun in a solvent, such as lyocell fibers, modal fibers or viscose fibers, and especially preferred are fibrillable fibers, for example lyocell fibers.

Particularly preferably, the fibers of regenerated cellulose have a mean length-weighted length of at least 3 mm and at most 100 mm, and most preferably at least 3 mm and at most 15 mm.

Particularly preferably, the fibers of regenerated cellulose have a length-related mass of at least 1.0 g/10000 m (1.0 dtex) and at most 8.0 g/10000 m (8.0 dtex), and most preferably at least 1.0 g/10000 m (1.0 dtex) and at most 6.0 g/10000 m (6.0 dtex).

The pulp fibers and the fibers of regenerated cellulose can be used in any desired mixing ratio, for example, based on the mass of the cellulose fibers in ratios of 0:100, 20:80, 50:50, 80:20 or 100:0.

The additive is preferably either triethyl citrate or triacetin, but not a mixture of these substances.

Preferably, the sum of the masses of the additive and the adhesion promoter in the filter material is at least 4% and at most 35%, and particularly preferably at least 5% and at most 25%, based on the mass of the filter material.

The adhesion promoter is preferably selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentandiol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, and glycerin diacetate, or is a mixture of two or more of these substances. Particularly preferably, the adhesion promoter is selected from the group consisting of 1,2-propanediol, 1,2-butanediol, and 2,3-butanediol, or is a mixture of two or more of these substances. Most preferably, the adhesion promoter is 1,2-propanediol.

The mixing ratio of additive and adhesion promoter is important and is advantageously selected such that the number of nonpolar groups of the adhesion promoter corresponds to the number of nonpolar groups of the additive. In preferred embodiments, the mixing ratio of additive and adhesion promoter is selected such that the number of nonpolar groups of the adhesion promoter and the number of nonpolar groups of the additive in the mixture differ from each other by less than 25%, preferably less than 20%, and particularly preferably by less than 15%. According to the inventors, the adhesion promoter can bind to the additive with its nonpolar groups and to the cellulose fibers with its polar groups, thus significantly restricting the mobility of the additive and thereby reducing migration.

Preferably, the ratio of the mass of the additive to the mass of the adhesion promoter is at least 1:2 and at most 2:1, particularly preferably at least 2:3 and at most 3:2.

For example, triethyl citrate has a molar mass of 276.29 g/mol and three nonpolar groups to which the adhesion promoter can bind. The adhesion promoter 1,2-propanediol has a molar mass of 76.09 g/mol and possesses one nonpolar group with which it can bind to the triethyl citrate. According to the inventors, a molar ratio of 1:3 is therefore particularly advantageous for this combination of additive and adhesion promoter. This molar ratio corresponds to a mass ratio of additive to adhesion promoter of 1.21. If, on the other hand, 1,2-butanediol or 1,3-butanediol, with a molar mass of 90.12 g/mol, is used as the adhesion promoter, the same considerations result in a favorable mass ratio of additive to adhesion promoter of 1.02.

In a particularly preferred embodiment, the additive is triethyl citrate and the adhesion promoter is 1,2-propanediol, and the ratio of the masses of triethyl citrate to 1,2-propanediol is at least 1.00 and at most 1.40, and most preferably at least 1.10 and at most 1.30.

In a particularly preferred embodiment, the additive is triethyl citrate and the adhesion promoter is 1,2-butanediol or 1,3-butanediol or a mixture thereof, and the ratio of the mass of triethyl citrate to the mass of the adhesion promoter is at least 0.80 and at most 1.20, and most preferably at least 0.90 and at most 1.10.

Similarly, triacetin has a molar mass of 218.21 g/mol and three nonpolar groups to which the adhesion promoter can bind. The adhesion promoter 1,2-propanediol has a molar mass of 76.09 g/mol and possesses a nonpolar group that allows it to bind to triacetin. According to the inventors, a molar ratio of 1:3 is therefore particularly advantageous for this combination of additive and adhesion promoter. This molar ratio corresponds to a mass ratio of additive to adhesion promoter of 0.96. If, on the other hand, 1,2-butanediol or 1,3-butanediol, with a molar mass of 90.12 g/mol, is used as the adhesion promoter, the same considerations result in a favorable mass ratio of additive to adhesion promoter of 0.81.

In a particularly preferred embodiment, the additive is triacetin and the adhesion promoter is 1,2-propanediol, and the ratio of the masses of triacetin to 1,2-propanediol is at least 0.75 and at most 1.15, and most preferably at least 0.85 and at most 1.05.

In a particularly preferred embodiment, the additive is triacetin and the adhesion promoter is 1,2-butanediol or 1,3-butanediol or a mixture thereof, and the ratio of the mass of triacetin to the mass of the adhesion promoter is at least 0.60 and at most 1.00, and most preferably at least 0.70 and at most 0.90.

Preferably, the cellulose fiber-based substrate is a paper, a nonwoven fabric, a continuous strand or a yarn.

In a particularly preferred embodiment of the filter material, the cellulose fiber-based substrate is a paper with a basis weight of at least 10 g/ ^m² and at most 60 g/ ^m² , most preferably at least 12 g/ ^m² and at most 50 g/ ^m² . In this particularly preferred embodiment of the filter material, the paper can comprise a filler, wherein at most 30%, most preferably at most 10%, of the mass of the paper is formed by the filler, and wherein the filler is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, magnesium silicate, aluminum silicate, kaolin, talc, and bentonite, or a mixture thereof.

In a particularly preferred embodiment of the filter material, the cellulose fiber-based substrate is a nonwoven fabric with a basis weight of at least 30 g/ ^m² and at most 500 g/ ^m² , most preferably at least 35 g/ ^m² and at most 300 g/ ^m² , and particularly preferably at least 40 g/ ^m² and at most 200 g/ ^m² . In this particularly preferred embodiment of the filter material, the nonwoven fabric can comprise a binder, wherein at most 30%, and most preferably at most 10%, of the mass of the nonwoven fabric is formed by the binder, and the binder is selected from the group consisting of sizing agents, alkyl ketene dimers (AKD), alkenylsuccinic anhydrides (ASA), fatty acids, starch, starch derivatives, carboxymethylcellulose, alginates, chitosan, wet-strength agents, pectin, guar gum, and agar-agar, or a mixture thereof. In this particularly preferred embodiment, the nonwoven fabric can be a wet-needled or a mechanically needled nonwoven fabric.

The filter material may comprise further substances which a person skilled in the art may select according to their experience to impart special properties to the filter material. Preferably, the substances are selected from the group consisting of sizing agents, alkyl ketene dimers (AKDs), alkenylsuccinic anhydrides (ASA), fatty acids, starch, starch derivatives, carboxymethylcellulose, alginates, chitosan, wet-strength agents, trisodium citrate, tripotassium citrate, malates, tartrates, acetates, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxylates, salicylates, α-hydroxycaprylates, phosphates, polyphosphates, chlorides, hydrogen carbonates, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, catalysts, activated carbon, flavorings, encapsulated flavorings, dyes, pigments, thermochromic dyes, hydrochromic dyes, and mixtures thereof.

The filter material according to the invention can be produced using prior art methods, wherein the additive and the adhesion promoter can be applied to the cellulose fiber-based substrate, for example, in the size press or film press of a paper machine, by a printing process such as gravure, reverse gravure, or flexographic printing, by spraying, or by impregnation. In general, the additive and adhesion promoter can be applied together. The additive and the adhesion promoter can also be applied during the production of the filter, for example, by spraying, so that the filter material according to the invention is formed during the production of the filter.

Another aspect of the invention relates to a segment comprising the filter material according to the invention. The segment according to the invention for a smoking product comprises the filter material according to one of the embodiments described above and a covering material, wherein the covering material encloses the filter material and is preferably a paper, a film or a laminate.

The covering material of the segment according to the invention preferably has a basis weight of at least 20 g/ ^m² and at most 150 g/ ^m² . Particularly preferably, the coating material has a basis weight of at least 30 g/ ^m² and at most 130 g/ ^m² . A coating material with this preferred or particularly preferred basis weight, in combination with the filter material, imparts a particularly advantageous hardness to the coated segment according to the invention. This prevents the smoker from accidentally compressing the segment within the smoking product. In a particularly preferred embodiment, the coating material is a laminate of two layers, and most preferably a laminate of two paper layers. This allows for even greater hardness to be achieved with less material than with a single-layer coating material.

In a preferred embodiment of the segment according to the invention, the segment is cylindrical with a cross-sectional area having an outer boundary that is at least approximately circular or oval, wherein the diameter of this boundary is at least 3 mm and at most 10 mm, particularly preferably at least 4 mm and at most 9 mm, and most preferably at least 5 mm and at most 8 mm. These diameters are advantageous for the use of the segments according to the invention in smoking articles. The diameter can be determined according to ISO 2971:2013.

In a preferred embodiment of the segment according to the invention, the segment has a length of at least 4 mm and at most 40 mm, particularly preferably at least 6 mm and at most 35 mm and most preferably at least 10 mm and at most 28 mm.

The draw resistance of the segment determines, among other things, the pressure differential the smoker must exert to generate a specific volume flow through the smoking product, and therefore significantly influences the smoker's acceptance of the product. The draw resistance of the segment can be measured according to ISO 6565:2015 and is expressed in mm water column (mmWG). To a very good approximation, the draw resistance of the segment is directly proportional to its length, meaning that the measurement can also be performed on rods, for example, with a length of up to 150 mm, which differ from the segment only in length. From this, the draw resistance of the segment can generally be easily calculated, especially for segment lengths from 3 mm to 50 mm.

The tensile resistance of the segment per unit length of the segment is preferably at least 0.05 mmWG/mm and at most 12.0 mmWG/mm, particularly preferably at least 0.1 mmWG/mm and at most 10.0 mmWG/mm and most preferably at least 0.1 mmWG/mm and at most 8.0 mmWG/mm.

The segment typically has a substantially cylindrical shape with an approximately circular or oval outer boundary of the cross-sectional area and may contain one or more cavities within it, for example, to hold activated carbon particles or breakable capsules containing flavorings. The cavities may also be formed as one or more elongated tubes that run at least approximately parallel to the segment's longitudinal axis and are located entirely within the segment or terminate at one or both of its end faces. Such cavities can also affect filtration efficiency and draw resistance. The direction of the longitudinal axis corresponds to the flow direction of the aerosol within the smoking device when the smoker inhales during use.

In a preferred embodiment of the segment according to the invention, the segment is a hollow cylinder, wherein the outer diameter of the hollow cylinder is at least 4 mm and at most 10 mm, particularly preferably at least 5 mm and at most 9 mm, and the outer diameter of the hollow cylinder is at least 1 mm larger than the inner diameter of the hollow cylinder, and the inner diameter is at least 10% and at most 85% of the outer diameter. In this preferred embodiment, the tensile resistance of the segment per unit length of the segment is at least 0.05 mmWG/mm and at most 1.0 mmWG/mm, most preferably at least 0.05 mmWG/mm and at most 0.5 mmWG/mm.

The segment according to the invention can also contain an aerosol-forming material, in particular a tobacco material.

The production of a segment according to the invention can be carried out using methods known in the prior art.

Another aspect of the invention relates to a smoking article comprising a segment that is at least partially formed by the filter material according to the invention. The smoking article according to the invention comprises at least one aerosol-generating material and a segment according to one of the embodiments described above.

In a preferred embodiment, the smoking article is a filter cigarette, wherein the aerosol-forming material comprises tobacco and the segment has a draw resistance of at least 30 mmWG and at most 120 mmWG. In a further embodiment In a preferred embodiment, the smoking product is a filter cigarette, wherein the aerosol-forming material comprises tobacco and the segment has a draw resistance per unit length of at least 1 mmWG/mm and at most 5 mmWG/mm. For filter cigarettes, high filtration efficiency is of paramount importance, which is why a comparatively high draw resistance of the segment is advantageous.

In a preferred embodiment, the smoking article is a tobacco heater in which, during use, the aerosol-forming material is only heated but not burned, and the aerosol-forming material comprises a material selected from the group consisting of tobacco, reconstituted tobacco, nicotine, glycerol, propylene glycol, and flavorings, or a mixture of two or more of these materials, and the segment has a draw resistance of at least 5 mmWG and at most 50 mmWG, particularly preferably at least 10 mmWG and at most 40 mmWG. In a further preferred embodiment, the smoking device is a tobacco heater in which the aerosol-generating material is only heated but not burned during use. The aerosol-generating material comprises a material selected from the group consisting of tobacco, reconstituted tobacco, nicotine, glycerol, propylene glycol, and flavorings, or a mixture of two or more of these materials. The segment has a draw resistance per unit length of the segment of at least 0.1 mmWG/mm and at most 3 mmWG/mm, particularly preferably at least 0.2 mmWG/mm and at most 2.5 mmWG/mm. With tobacco heaters, there is an interest in filtering the aerosol minimally but cooling it somewhat within the segment. Therefore, a low draw resistance is advantageous. In a particularly preferred embodiment of this smoking device, the aerosol-generating material is provided for electrical heating. For this purpose, the smoking device can be electrically heated in a separate device.

In a preferred embodiment, the smoking device is an electronic cigarette or a vaporizer, wherein the aerosol-forming material is a liquid, particularly preferably containing nicotine, and the segment has a draw resistance of at least 5 mmWG and at most 50 mmWG, particularly preferably at least 10 mmWG and at most 40 mmWG. In a further preferred embodiment, the smoking device is an electronic cigarette or a vaporizer, wherein the aerosol-forming material is a liquid, particularly preferably containing nicotine, and the segment has a draw resistance per unit length of the segment of at least 0.1 mmWG/mm and at most 3 mmWG/mm, particularly preferably at least 0.2 mmWG/mm and at most 2.5 mmWG/mm. As with heated tobacco products, a low draw resistance of the segment is also advantageous for electronic cigarettes or vaporizers.

The smoking article according to the invention can be manufactured using methods known in the prior art.

DESCRIPTION OF THE PREFERRED EXECUTION FORMS AND SOME COMPARATIVE EXAMPLES

In the following, some preferred embodiments of a segment according to the invention are described and compared with examples not according to the invention.

Comparative example 1

A Benson & Hedges brand filter cigarette was produced from a 27 mm long cylindrical segment of cellulose acetate with a diameter of 7.84 mm and a draw resistance of 80 mmWG. The cigarette contained an American Blend tobacco mixture, a filter ventilation rate of 42.6%, and a closed draw resistance of 120.5 mmWG. The filter cigarette was smoked according to the procedure specified in ISO 3308:2012 and ISO 4387:2019, and the phenol content of the smoke was determined. The amount of phenols was 10.1 µg.

For the other filter materials according to the invention and for comparative examples not according to the invention, a filter paper was used as a cellulose fiber-based substrate. The filter paper had a basis weight of 35 g/ ^m² and consisted of 80% cellulose fibers from coniferous trees and 20% cellulose fibers from deciduous trees, each based on the mass of the filter paper. The filter paper had a thickness of 90 µm and a breaking strength of 15 N/15 mm.

Comparative example 2

A 27 mm long segment with a draw resistance of approximately 80 mmWG was produced from the filter paper, and a filter cigarette otherwise identical to comparison example 1 was manufactured using this segment. The filter cigarette was then produced according to the procedure described in ISO 3308:2012 and ISO 4387:2019 The specified procedure was used to smoke the filter cigarette, and the phenol content in the smoke was determined. The amount of phenols was 15.5 µg.

Comparison examples 1 and 2 show that, with comparable tensile resistance, a cellulose fiber-based filter paper has a significantly lower filtration rate. has a higher ration efficiency for phenols than cellulose acetate.

Comparative example 3

Another filter material not according to the invention was produced by applying triethyl citrate to the filter paper in a reverse gravure printing process in an amount of 7% of the filter paper's mass. A 27 mm long segment with a draw resistance of approximately 80 mmWG was produced from the filter material, and a filter cigarette otherwise identical to Comparative Example 1 was manufactured using this segment. The filter cigarette was smoked according to the method specified in ISO 3308:2012 and ISO 4387:2019, and the phenol content in the smoke from the filter cigarette was determined. The amount of phenols was 9.0 µg.

The filter cigarette consisted of a filter segment wrapped in filter paper with a basis weight of 78 g/ ^m² , a tobacco segment wrapped in standard cigarette paper, and a tipping paper that wrapped and bound the filter segment and part of the tobacco segment. The filter cigarette was stored for three months at 22°C and 60% relative humidity, after which the triethyl citrate content of the tipping paper was determined. A content of 8.3% of the tipping paper's mass was found.

Comparative example 4

Another filter material not according to the invention was produced by applying triethyl citrate to the filter paper in a reverse gravure printing process in an amount of 20% of the mass of the filter paper. A 27 mm long segment with a draw resistance of approximately 80 mmWG was produced from the filter material, and a filter cigarette otherwise identical to Comparative Example 1 was manufactured using this segment. The filter cigarette was produced according to the procedure described in ISO 3308:2012 and ISO 4387:2019 The specified procedure was followed, and the phenol content of the filter cigarette smoke was determined. The amount of phenols was 4.8 µg.

Comparison examples 3 and 4 show that triethyl citrate is suitable for increasing the filtration efficiency for phenols and that a higher amount of triethyl citrate also leads to an increase in the filtration efficiency for phenols. According to comparison example 3, to achieve a filtration efficiency for phenols similar to that of the cellulose acetate segment in comparison example 1, an amount of slightly less than 7% triethyl citrate, based on the mass of the filter paper, is sufficient. Comparison example 3 also shows that after storage of 3 months, a significant amount of the triethyl citrate migrates into the tipping paper.

Exemplary embodiment according to the invention 5

A filter material according to the invention was produced by applying a mass-based 1:1 mixture of triethyl citrate and 1,2-propanediol to the filter paper in a reverse gravure printing process in an amount of 14% of the mass of the filter paper. A 27 mm long segment with a draw resistance of approximately 80 mmWG was produced from the filter material, and a filter cigarette otherwise identical to Comparative Example 1 was manufactured using this segment. The filter cigarette was produced according to the process described in ISO 3308:2012 and ISO 4387:2019 The specified procedure was followed, and the phenol content of the filter cigarette smoke was determined. The amount of phenols was 6.8 µg.

In the inventive embodiment 5, in comparison to example 3, the additional application of 7% 1,2-propanediol has a small, positive influence on the filtration efficiency for phenols.

Exemplary embodiment according to the invention 6

A filter material according to the invention was produced by applying a 1:1 mixture of triethyl citrate and 1,2-propanediol, based on mass, to the filter paper in a reverse gravure printing process in an amount of 16% of the mass of the filter paper. A 27 mm long segment with a draw resistance of approximately 80 mmWG was produced from the filter material, and a filter cigarette otherwise identical to Comparative Example 1 was manufactured using this segment.

The filter cigarette, apart from the filter material, consisted of the same components as the filter cigarette from comparison example 3 and was stored together with the filter cigarette from comparison example 3 for three months at 22°C and 60% relative humidity. Afterwards, the triethyl citrate content in the tipping paper was determined. A content of 1.6% of the mass of the tipping paper was found.

Exemplary embodiment according to the invention 7

From the filter material according to the invention of embodiment 5, a filter rod in the form of a hollow cylinder with a length of 108 mm, an outer diameter of 7.4 mm and an inner diameter of 3.0 mm was produced. The filter rod had a tensile resistance of 14.9 mmWG, i.e. a length-related tensile resistance of 0.14 mmWG/mm, so that a segment made from it with a length of 27 mm has a tensile resistance of 3.73 mmWG.

In comparison to example 3, embodiment 6 of the invention shows that, despite a higher triethyl citrate content of 8%, the amount of triethyl citrate migrated into the tipping paper is significantly lower, amounting to only 1.6% of the tipping paper's mass, whereas in example 3 it exceeds 8% of the tipping paper's mass. This demonstrates that by applying a mixture of an additive, such as triethyl citrate, and an adhesion promoter, such as 1,2-propanediol, the migration of the additive can be considerably reduced, while the filtration properties remain essentially unchanged. This effectively prevents contamination of other components of the smoking product.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2 515 689 [0008]

Cited non-patent literature

• ISO 3308:2012 [0057, 0061, 0063]
• ISO 4387:2019 [0057, 0061, 0063]

Claims (43)

Filter material comprising a cellulose fiber-based substrate, an additive, and an adhesion promoter, wherein the mass ratio of the additive and the adhesion promoter is at least 1:3 and at most 2:1, and the additive and the adhesion promoter together constitute at least 3% and at most 40% of the mass of the cellulose fiber-based substrate, where the additive is triethyl citrate, triacetin, or a mixture of these substances, and where the adhesion promoter is selected from the group consisting of ethanediol, propanediol, butanediol, pentanediol, and glycerin diacetate, or mixtures thereof. Filter material according to Claim 1 , wherein the cellulose fiber-based substrate comprises cellulose fibers, wherein preferably at least 70%, preferably at least 90% and most preferably at least 99% of the mass of the cellulose fiber-based substrate is formed by cellulose fibers. Filter material according to Claim 2 , in which the cellulose fibers are pulp fibers, fibers of regenerated cellulose or a mixture thereof. Filter material according to one of the Claims 2 or 3 , in which the pulp fibers are pulp fibers obtained from coniferous trees, deciduous trees or other plants, in particular hemp, flax, jute, ramie, kenaf, kapok, coconut, abacá, sisal, bamboo, cotton or esparto grass, or a mixture of pulp fibers from two or more of these trees or plants. Filter material according to Claim 4 , in which the cellulose fibers are cellulose fibers obtained from hemp, flax, jute, coconut, abacá, sisal or cotton, or a mixture of cellulose fibers from two or more of these plants. Filter material according to Claim 3 , wherein the fibers of regenerated cellulose are fibers spun in a solvent, in particular lyocell fibers, modal fibers or viscose fibers, and most preferably are fibrillable fibers of regenerated cellulose. Filter material according to Claim 3 or 6 , wherein the fibers of regenerated cellulose have a mean length-weighted length of at least 3 mm and at most 100 mm and preferably of at least 3 mm and at most 15 mm. Filter material according to Claim 3 , 6 or 7 , wherein the fibers of regenerated cellulose have a linear mass of at least 1.0 g/10000 m (1.0 dtex) and at most 8.0 g/10000 m (8.0 dtex), preferably at least 1.0 g/10000 m (1.0 dtex) and at most 6.0 g/10000 m (6.0 dtex). Filter material according to one of the preceding claims, wherein the additive is either triethyl citrate or triacetin, but not a mixture of these substances. Filter material according to one of the preceding claims, wherein the sum of the masses of the additive and the adhesion promoter in the filter material is at least 4% and at most 35%, preferably at least 5% and at most 25%, in each case based on the mass of the filter material. Filter material according to one of the preceding claims, wherein the adhesion promoter is selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol and glycerin diacetate, or a mixture of two of these substances. Filter material according to Claim 11 , in which the adhesion promoter is selected from the group consisting of 1,2-propanediol, 1,2-butanediol and 2,3-butanediol, or a mixture of two or more of these substances. Filter material according to Claim 12 , in which the adhesion promoter is 1,2-propanediol. Filter material according to one of the preceding claims, wherein a mixing ratio of additive and adhesion promoter is selected such that the number of nonpolar groups of the adhesion promoter and the number of nonpolar groups of the additive in the mixture differ from each other by less than 25%, preferably less than 20% and most preferably by less than 15%. Filter material according to one of the preceding claims, wherein the ratio of the mass of the additive to the mass of the adhesion promoter is at least 1:2 and at most 2:1, preferably at least 2:3 and at most 3:2. Filter material according to one of the preceding claims, wherein the additive is triethyl citrate and the adhesion promoter is 1,2-propanediol, and wherein the ratio of the mass of triethyl citrate to the mass of 1,2-propanediol is at least 1.00 and at most 1.40, preferably at least 1.10 and at most 1.30. Filter material according to one of the Claims 1 until 15 , wherein the additive is triethyl citrate and the adhesion promoter is 1,2-butanediol or 1,3-butanediol or a mixture thereof, and wherein the ratio of the mass of triethyl citrate to the mass of the adhesion promoter is at least 0.80 and at most 1.20, preferably at least 0.90 and at most 1.10. Filter material according to one of the Claims 1 until 15 , wherein the additive is triacetin and the adhesion promoter is 1,2-propanediol, and wherein the ratio of the mass of triacetin to the mass of 1,2-propanediol is at least 0.75 and at most 1.15, preferably at least 0.85 and at most 1.05. Filter material according to one of the Claims 1 until 15 , wherein the additive is triacetin and the adhesion promoter is 1,2-butanediol or 1,3-butanediol or a mixture thereof, and wherein the ratio of the mass of triacetin to the mass of the adhesion promoter is at least 0.60 and at most 1.00, preferably at least 0.70 and at most 0.90. Filter material according to any of the preceding claims, wherein the cellulose fiber-based substrate is a paper, a nonwoven, an endless strand or a yarn. Filter material according to Claim 20 , wherein the cellulose fiber-based substrate is a paper with a basis weight of at least 10 g/m ² and at most 60 g/m ² , preferably at least 12 g/m ² and at most 50 g/m ² . Filter material according to Claim 20 or 21 , wherein the filter material is a paper comprising a filler, wherein at most 30%, preferably at most 10% of the mass of the paper is formed by the filler, and wherein the filler is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, magnesium silicate, aluminum silicate, kaolin, talc, and bentonite or mixtures thereof. Filter material according to Claim 20 , wherein the cellulose fiber-based substrate is a nonwoven fabric with a basis weight of at least 30 g/m ² and at most 500 g/m ² , preferably at least 35 g/m ² and at most 300 g/m ² and particularly preferably at least 40 g/m ² and at most 200 g/m ² . Filter material according to Claim 23 , wherein the nonwoven fabric comprises a binder, wherein at most 30%, preferably at most 10% of the mass of the nonwoven fabric is formed by the binder and the binder is selected from the group consisting of sizing agents, alkyl ketene dimers (AKD), alkenylsuccinic anhydrides (ASA), fatty acids, starch, starch derivatives, carboxymethylcellulose, alginates, chitosan, wet-strength agents, pectin, guar and agar agar or a mixture thereof. Filter material according to Claim 24 , where the nonwoven fabric is a wet-needled or mechanically needled nonwoven fabric. Segment for a smoking article comprising a filter material according to one of the preceding claims and a covering material, wherein the covering material encloses the filter material. Segment by Claim 26 , where the wrapping material is paper, film or laminate. Segment by Claim 26 or 27 , wherein the covering material has a basis weight of at least 20 g/m ² and at most 150 g/m ² , preferably at least 30 g/m ² and at most 130 g/m ² . Segment by Claim 27 or 28 , in which the covering material is a laminate of two layers, preferably of two layers of paper. Segment after one of the Claims 26 until 29 , wherein the segment is cylindrical and has a cross-sectional area having an outer boundary that is at least approximately circular or oval, wherein the diameter of this boundary is at least 3 mm and at most 10 mm, preferably at least 4 mm and at most 9 mm and particularly preferably at least 5 mm and at most 8 mm. Segment after one of the Claims 26 until 30 , which has a length of at least 4 mm and at most 40 mm, preferably at least 6 mm and at most 35 mm and particularly preferably at least 10 mm and at most 28 mm. Segment after one of the Claims 26 until 31 , whose tensile resistance per length of the segment is at least 0.05 mmWG/mm and at most 12.0 mmWG/mm, preferably at least 0.1 mmWG/mm and at most 10.0 mmWG/mm and particularly preferably at least 0.1 mmWG/mm and at most 8.0 mmWG/mm. Segment after one of the Claims 26 until 32 , which has one or more cavities inside, in which activated carbon particles or at least one breakable capsule filled with flavorings are contained. Segment after one of the Claims 26 until 33 , which has inside it one or more cavities in the form of elongated tubes that run at least approximately parallel to a longitudinal axis of the segment and are located entirely within the segment or end at one or both end faces of the segment. Segment after one of the Claims 26 until 34 , wherein the segment forms a hollow cylinder with an inner and an outer diameter, wherein the outer diameter of the hollow cylinder is at least 4 mm and at most 10 mm, preferably at least 5 mm and at most 9 mm, wherein the outer diameter of the hollow cylinder is at least 1 mm larger than the inner diameter of the hollow cylinder and the inner diameter is at least 10% and at most 85% of the outer diameter, and wherein the tensile resistance of the segment per length of the segment is at least 0.05 mmWG/mm and at most 1.0 mmWG/mm, preferably at least 0.05 mmWG/mm and at most 0.5 mmWG/mm. Segment after one of the Claims 26 until 35 , wherein the segment contains an aerosol-forming material, in particular a tobacco material. Smoking articles comprising at least one aerosol-forming material and a segment following one of the Claims 26 until 36 . Tobacco products Claim 37 , wherein the smoking article is a filter cigarette, the aerosol-forming material comprises tobacco, and the segment has a draw resistance of at least 30 mmWG and at most 120 mmWG. Tobacco products Claim 37 , wherein the smoking article is a filter cigarette, the aerosol-forming material comprises tobacco, and the segment has a draw resistance per segment length of at least 1 mmWG/mm and at most 5 mmWG/mm. Tobacco products Claim 37 , wherein the smoking article is a tobacco heater in which, during use, the aerosol-forming material is only heated but not burned, the aerosol-forming material comprises a material selected from the group consisting of tobacco, reconstituted tobacco, nicotine, glycerol, propylene glycol, and flavorings, or a mixture of two or more of these materials, and the segment has a draw resistance of at least 5 mmWG and at most 50 mmWG, preferably at least 10 mmWG and at most 40 mmWG. Tobacco products Claim 37 , wherein the smoking article is a tobacco heater in which, during use, the aerosol-forming material is only heated but not burned, the aerosol-forming material comprises a material selected from the group consisting of tobacco, reconstituted tobacco, nicotine, glycerol, propylene glycol, and flavorings, or a mixture of two or more of these materials, and the segment has a draw resistance per length of the segment of at least 0.1 mmWG/mm and at most 3 mmWG/mm, preferably at least 0.2 mmWG/mm and at most 2.5 mmWG/mm. Tobacco products Claim 37 , wherein the smoking article is an electronic cigarette or a vaporizing device, wherein the aerosol-forming material is a liquid preferably containing nicotine, and the segment has a draw resistance of at least 5 mmWG and at most 50 mmWG, preferably at least 10 mmWG and at most 40 mmWG. Tobacco products Claim 37 , wherein the smoking article is an electronic cigarette or a vaporizing device, wherein the aerosol-forming material is a liquid preferably containing nicotine, and the segment has a draw resistance per length of the segment of at least 0.1 mmWG/mm and at most 3 mmWG/mm, preferably at least 0.2 mmWG/mm and at most 2.5 mmWG/mm.