Patent Application
20240245105
The invention relates to a filter material suitable for manufacturing a segment in a smoking article, which has an advantageous plastic deformability in the cross direction, so that segments for smoking articles can be manufactured therefrom in an efficient manner. The invention also relates to a segment for a smoking article, manufactured from this filter material.
Smoking articles are typically rod-shaped articles, which consist of at least two rod-shaped segments disposed next to each other. One segment contains a material which is capable of forming an aerosol upon heating and at least one further segment serves to influence the properties of the aerosol.
The smoking article can be a filter cigarette in which a first segment contains the aerosol-forming material, in particular tobacco, and in which a further segment is designed as a filter and acts to filter the aerosol. In this regard, the aerosol is generated by combustion of the aerosol-forming material and the filter serves primarily to filter the aerosol and to provide the filter cigarette with a defined draw resistance.
The smoking article, however, can also be what is known as a heated tobacco product, wherein the aerosol-forming material is only heated but not burned. This means that the number and amount of substances in the aerosol which are damaging to health are reduced. Such a smoking article also consists of at least two, more often, however, of more, in particular of four segments. One segment contains the aerosol-forming material, which typically comprises tobacco, reconstituted tobacco or tobacco prepared by other processes. Further, optional segments in the heated tobacco product serve to transfer the aerosol, to cool the aerosol or to filter the aerosol.
The segments are usually wrapped with a wrapper material. Very often, paper is used as wrapper material.
Unless it is explicitly stated below or is directly clear from the context, the “segment” should be understood to refer to the segment of a smoking article that does not contain the aerosol-forming material, but rather serves, for example, to transfer, cool or filter the aerosol.
In the prior art, forming such segments from polymers such as cellulose acetate or polylactides is known. After consumption of the smoking article, the smoking article has to be disposed of properly. In many cases, however, the consumer simply disposes of the spent smoking article in the environment, and attempts to restrict this behavior by information or fines have had little success.
Because cellulose acetate and polylactides biodegrade only very slowly in the environment, there is an interest in the industry in manufacturing the segments of the smoking article from other materials that biodegrade better. Furthermore, in the European Union, for example, regulations are under discussion to substantially reduce or prohibit the use of non-natural polymers in smoking articles, so that for this reason too, there is an interest in having alternative segments for smoking articles available.
It is known in the prior art to manufacture segments for smoking articles, in particular filter segments, from paper. Such segments are generally readily biodegradable, but also suffer from disadvantages. As an example, filter segments from paper generally have a high filtration efficiency and thus lead to a dry aerosol, which deteriorates the taste of the aerosol compared with cigarettes with conventional filter segments from cellulose acetate. Furthermore, they often have a lower filtration efficiency for phenols than cellulose acetate.
An essential reason as to why filter segments from paper are not yet in widespread use is also their optical appearance. At the mouth end of the smoking article, the cut surface of the segment located at the mouth end is visible, and from the usual segments produced from cellulose acetate, the consumer is used to a white homogeneous surface, in which the individual cut fibers are hardly visible. Segments from paper, however, have a coarse structure, which provides an impression of lower quality to the consumer. Therefore, segments produced from paper are often only used as a part of a segment in a filter composed of several segments, so that the consumer cannot see the cut surface. The segment located at the mouth end is then often still produced from cellulose acetate. Because of these optical defects, the advantages regarding biodegradability of a segment from paper cannot be fully exploited.
In the prior art, it is also known to manufacture segments for smoking articles from nonwovens. In EP 2 515 689, for example, a filter material from a nonwoven is described which, however, contains mainly fibers from polyvinyl alcohol, polylactides or other non-natural polymers and thus does not fully meet the requirements regarding biodegradability. Furthermore, the nonwovens described there are too thin to result in an optically acceptable appearance of the cut surface of a segment manufactured therefrom.
It is also known in the art to manufacture filter material for smoking articles from paper from easily biodegradable fibers. In US 2015/0374030, such a filter material is described which, however, consists to a substantial extent of pulp fibers from hemp, flax, abaca, sisal or cotton. These fibers are expensive and their quality varies widely due to their short growth period compared with pulp fibers from wood. According to the teaching of US 2015/0374030, though, they are necessary in order to achieve a sufficiently porous structure and a sufficiently high strength at the same time. The use of wood pulp is discouraged, because it produces a dense and compact paper structure. In fact, the proportion of wood pulp should always be less than 50% by weight and in the embodiments implemented industrially, it is less than 5% by weight. In addition, the optical appearance of such filters is not sufficiently appealing to the consumer because of the production process employed.
Contrary to the teachings in the prior art, the inventors have found in the present application that a filter material with a high proportion of pulp fibers can be manufactured in the form of a hydroentangled nonwoven, without making the structure of the nonwoven too dense or too compact. A corresponding filter material, which can be seen as a starting point of the present invention, is described in the not pre-published international application PCT/EP2019/085125. In this not pre-published application, pleating or crimping of the filter material is also described in order to form a continuous tow of pleated or crimped filter material, which afterwards is wrapped with wrapper paper and cut into individual rods of defined length in order to form said segments.
As an example, during the manufacture of a segment, it is possible to initially crimp a cellulose-based nonwoven in the longitudinal direction, before forming it into a continuous tow and wrapping it with a wrapper material. Then the continuous tow can be cut into pieces suitable for further processing.
During crimping of the web, the web can be passed through two rollers provided with a pattern, which emboss this pattern onto the web. As an example, this pattern can be a line pattern oriented in the machine direction of the web. The embossed lines stretch and deform the web in the direction orthogonal to the machine direction, the cross direction, so that then, a continuous tow can be formed more easily by gathering the web in the cross direction.
During the described type of crimping, however, it can happen that the web tears in the cross direction. Thus, there is a need for a filter material that does not have this disadvantage or only to a lesser extent, but otherwise is as identical as possible to other preferred filter materials, in particular to those that are described in the aforementioned not pre-published application PCT/EP2019/085125.
An objective of the invention is to provide a web-shaped filter material for a smoking article that can be processed into a segment of a smoking article with high productivity and that with respect to its properties is otherwise as similar as possible to preferred filter materials.
This objective is achieved by a hydroentangled nonwoven as claimed in claim 1, a segment for a smoking article according to claim 16, and a smoking article according to claim 23, as well as by a process for manufacturing a segment according to claim 22 and a process for manufacturing the hydroentangled nonwoven according to the invention according to claim 27. Advantageous embodiments are provided in the dependent claims.
The inventors have found that this objective can be achieved by a filter material for manufacturing a segment for a smoking article, wherein the filter material is a web-shaped hydroentangled nonwoven. Although the term “hydroentangled” initially indicates the basic manufacturing process, it has to be considered that a hydroentangled nonwoven has characteristic structural properties that differentiate it from other nonwovens and that, to the knowledge of the inventors, cannot be obtain in an identical manner by other production processes. Other than, for example, with paper, in which the strength is caused by hydrogen bonds and the fibers are primarily oriented in the plane of the paper, the strength of the hydroentangled nonwoven is achieved by an entanglement of the fibers. A hydroentangled nonwoven has a particularly porous structure, which makes it particularly suitable as filter material for segments of smoking articles.
According to the invention, the hydroentangled nonwoven contains at least 50% and at most 100% cellulose fibers, each with respect to the mass of the hydroentangled nonwoven, wherein the hydroentangled nonwoven has a basis weight of at least 15 g/m2 and at most 60 g/m2. In this regard, the hydroentangled nonwoven has a machine direction and a cross direction orthogonal thereto, lying in the plane of web of the hydroentangled nonwoven. Furthermore, the hydroentangled nonwoven has a characteristic plastic deformability in the cross direction which is characterized in that in a tensile test in the cross direction in accordance with ISO 1924-2:2008, the nonlinear portion of the deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break is at least 10% and at most 50% of the total deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break. This characteristic plastic deformability is more strongly pronounced than is the case with common filter materials.
During manufacturing and processing of the hydroentangled nonwoven, the hydroentangled nonwoven runs in a direction, the so-called machine direction, through the machine and the hydroentangled nonwoven has a direction orthogonal to the machine direction lying in the plane of the web of hydroentangled nonwoven, the cross direction.
During processing of the filter material to form a segment of a smoking article, the hydroentangled nonwoven is preferably crimped. To this end, the hydroentangled nonwoven is, for example, passed through two rolls provided with a pattern, which emboss this pattern onto the web. Preferably, this pattern is a line pattern oriented in the machine direction of the web. The embossed lines stretch and deform the hydroentangled nonwoven in the direction orthogonal to the machine direction, the cross direction. A filter material deformed in this manner can be gathered more easily in the cross direction, and thus a continuous tow can be produced for manufacturing the segments.
A problem with this process is that the two rolls produce a high elongation in the cross direction on the web, in order to cause the desired deformation of the hydroentangled nonwoven, and thus there is the danger that the hydroentangled nonwoven will tear in the cross direction. The skilled person could now be tempted to increase the elongation at break of the hydroentangled nonwoven in the cross direction, so that the hydroentangled nonwoven tolerates larger deformations without tearing. The inventors, however, have found that this does not solve the problem, because in order to achieve a permanent deformation in the cross direction, the elongation has to be increased even further, so that the danger of exceeding the breaking strength in the cross direction increases further.
According to the findings of the inventors, it is more important that, at the elongation in the cross direction to which the hydroentangled nonwoven is exposed during crimping, a permanent, plastic and not elastic deformation is caused. If such a plastic deformation can already be achieved with a greater separation of the rolls during crimping, the danger that the hydroentangled nonwoven tears in the cross direction during processing is reduced. Generally, it should be sufficient to stretch the filter material in the cross direction up to about half of its elongation at break.
The inventors have now found that by using suitable processes, the hydroentangled nonwoven can be provided with a structure that produces a good plastic deformability in the cross direction and thus simplifies crimping. Processes suitable therefore are explained further below.
This plastic deformability in the cross direction can be characterized in a tensile test in accordance with ISO 1924-2:2008. In this tensile test, a strip with a width of 15 mm is taken from the sample in the cross direction and is stretched at a speed of 20 mm/min until it breaks. During this, the elongation ε and the applied force F are recorded, so that a force-elongation-curve F(ε) results. Similarly, the elongation at break εb and the tensile strength F(εb) are recorded. The deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break, εb/2, is then
wherein in practice, the integral is calculated numerically.
This deformation energy consists of an elastic and a plastic portion. The elastic deformation energy is released upon removal of the load, so that it does not contribute to the result of the crimping. The plastic deformation, however, is irreversible, so that even at a smaller elongation through the two rolls, a good result for the crimping can be expected, if the portion of the plastic deformation energy with respect to the total deformation energy is higher than with comparable filter materials of the prior art.
The elastic deformation is generally associated with a proportionality between elongation and force. Under the fictitious assumption that the hydroentangled nonwoven behaves ideally elastically up to half the elongation at break, the deformation energy Elin up to half the elongation at break is calculated by
The nonlinear portion Enl of the deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break exceeding the linear deformation energy is then
According to the findings of the inventors, very good results during crimping can be achieved if the nonlinear portion of the deformation energy absorbed up to half the elongation at break in the cross direction is at least 10% of the total deformation energy absorbed up to half the elongation at break in the cross direction, i.e.
These considerations for quantifying the plastic behavior can be illustrated by the diagram shown in
During the manufacture of a segment from the hydroentangled nonwoven, the hydroentangled nonwoven can in certain locations be loaded, for example, up to about half the elongation at break εb/2, point 15, with the corresponding force F(εb/2), so that the state 16 is reached.
The line 17 which connects points 12 and 16 represents a fictitious linear elastic behavior and the linear deformation energy Elin corresponds to the area of the triangle formed by the points 12, 16 and 15. The total deformation energy, however, corresponds to the area enclosed by the lines from point 12 to point 15, from point 15 to point 16 and the line 13 from point 16 to point 12. The nonlinear portion Enl of the deformation energy, which is used for characterizing the hydroentangled nonwoven according to the invention in the context of this invention, corresponds to that area which is delimited by the lines 17 and 13, each between the points 12 and 16. The more strongly the force-elongation-curve bends upwards and the more it deviates from a fictitious linear elastic behavior, the greater is the potential for plastic and thus irreversible deformation.
During the manufacture of segments from the hydroentangled nonwoven according to the invention, the elongation in the cross direction can, of course, deviate from half the elongation at break during crimping, the nonlinear portion of the deformation energy up to half the elongation at break was, however, independent of the actually applied elongation and the actual elastic-plastic behavior, found to be a suitable parameter to characterize the structure of the hydroentangled nonwoven according to the invention and to predict the behavior of the hydroentangled nonwoven during crimping.
For comparison,
During the manufacture of a segment from the hydroentangled nonwoven, the hydroentangled nonwoven can, for example, be loaded up to about half the elongation at break εb/2, point 25, with the corresponding force F(εb/2), so that the state 26 is reached.
The line 27 connecting points 22 and 26 represents a linear elastic behavior and the corresponding deformation energy Elin corresponds to the area of the triangle formed by the points 22, 26 and 25. The total deformation energy E, however, corresponds to the area enclosed by the lines from point 22 to point 25, from point 25 to point 26 and by the line 23 from point 26 to point 22. The nonlinear portion Enl of the deformation energy corresponds to that area delimited by the lines 27 and 23, each between the points 22 and 26. It can be seen that at very similar elongations at break and very similar linear portions of the deformation energy, the portion of the nonlinear deformation energy is substantially smaller. Such a hydroentangled nonwoven will therefore react primarily elastically to a deformation and after removal of the load, will reverse essentially the entire deformation. In order to introduce a similar plastic deformation energy as for the hydroentangled nonwoven shown in
The hydroentangled nonwoven according to the invention contains cellulose fibers. According to the findings of the inventors, cellulose fibers are required to provide a sufficient strength to the hydroentangled nonwoven, so that it can be processed into a segment. According to the invention, the proportion of cellulose fibers in the hydroentangled nonwoven is at least 50% and at most 100% of the mass of the hydroentangled nonwoven; preferably, however, at least 60% and at most 100% and particularly preferably at least 70% and at most 95%, each with respect to the mass of the hydroentangled nonwoven.
The cellulose fibers can be pulp fibers or fibers from regenerated cellulose or mixtures thereof.
The pulp fibers are preferably sourced from coniferous woods, deciduous woods, or other plants such as hemp, flax, jute, ramie, kenaf, kapok, coconut, abacá, sisal, bamboo, cotton or from esparto grass. Mixtures of pulp fibers from various sources can also be used for manufacturing the hydroentangled nonwoven. Particularly preferably, the pulp fibers are sourced from coniferous woods, because even in small proportions, such fibers provide the hydroentangled nonwoven with good strength.
The hydroentangled nonwoven according to the invention can contain fibers from regenerated cellulose. Preferably, the proportion of fibers from regenerated cellulose is at least 5% and at most 50%, particularly preferably at least 10% and at most 45% and highly particularly preferably at least 15% and at most 40%, each with respect to the mass of the hydroentangled nonwoven.
The fibers from regenerated cellulose are preferably at least partially, in particular to more than 70%, formed by viscose fibers, Modal fibers, Lyocell® fibers, Tencel® fibers or mixtures thereof. These fibers have good biodegradability and can be used to optimize the strength of the hydroentangled nonwoven and to adjust the filtration efficiency of the segment manufactured therefrom for the smoking article. Due to the manufacturing process, they are less variable than the pulp fibers sourced from natural sources and contribute to the fact that the properties of a segment manufactured from the hydroentangled nonwoven vary less than if exclusively pulp fibers are used. Their manufacturing, however, requires more effort and usually they are also more expensive than pulp fibers.
According to the invention, the basis weight of the hydroentangled nonwoven is at least 15 g/m2 and at most 60 g/m2, preferably at least 18 g/m2 and at most 55 g/m2 and particularly preferably at least 20 g/m2 and at most 50 g/m2. The basis weight influences the tensile strength of the hydroentangled nonwoven, wherein a higher basis weight generally leads to a higher tensile strength. The basis weight should not be too high because then, the hydroentangled nonwoven could not be processed into segments for smoking articles at high speed. The values refer to a basis weight measured in accordance with ISO 536:2019.
For the hydroentangled nonwoven according to the invention, in a tensile test in the cross direction in accordance with ISO 1924-2:2008, the nonlinear portion of the deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break is at least 10% and at most 50% of the total deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break. Preferably, the nonlinear portion of the deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break is at least 15% and at most 40% of the total deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break, and particularly preferably, the nonlinear portion is at least 15% and at most 35%, and in particular at least 18% and at most 32%. In the preferred and particularly preferred intervals, a good result during crimping can be achieved even at a moderate elongation and the risk of the hydroentangled nonwoven tearing in the cross direction is particularly low.
To obtain specific properties, the hydroentangled nonwoven according to the invention can contain additives, such as alkyl ketene dimer (AKD), acid anhydrides such as alkenyl succinic acid anhydrides (ASA), polyvinyl alcohol, waxes, fatty acids, starch, starch derivatives, carboxy methyl cellulose, alginates, chitosan, wet strength agents or substances for adjusting the pH such as, for example, organic or inorganic acids or bases. Alternatively or additionally, the hydroentangled nonwoven according to the invention can also contain one or more additives that are selected from the group consisting of citrates such as trisodium citrate or tripotassium citrate, malates, tartrates, acetates such as sodium acetate or potassium acetate, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxalates, salicylates, α-hydroxy caprylates, phosphates, polyphosphates, chlorides and hydrogen carbonates, and mixtures thereof.
The skilled person is able to determine type and amount of such additives from his experience.
The hydroentangled nonwoven according to the invention can also comprise yet other substances which better match the filtration efficiency of the hydroentangled nonwoven to that of cellulose acetate. In a preferred embodiment, the hydroentangled nonwoven according to the invention comprises a substance selected from the group consisting of triacetin, propylene glycol, sorbitol, glycerol, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, triethyl citrate or mixtures thereof.
In a preferred embodiment of the hydroentangled nonwoven, at least a portion of the cellulose fibers is loaded with a filler, wherein the filler is particularly preferably formed by mineral particles and in particular by calcium carbonate particles. Because the structure of the hydroentangled nonwoven is very porous, it is not suitable for retaining fillers, so that it is advantageous to load the cellulose fibers with the fillers and thereby retain them in the structure of the hydroentangled nonwoven. Fillers can serve to provide special properties to the hydroentangled nonwoven.
The thickness of one layer of the hydroentangled nonwoven, measured in accordance with ISO 534:2011, is preferably at least 25 μm and at most 1000 μm, preferably at least 30 μm and at most 800 μm, particularly preferably at least 35 μm and at most 600 μm. The thickness influences the amount of hydroentangled nonwoven that can be packed into the segment of the smoking article, and therefore the draw resistance and the filtration efficiency of the segment, but also the processability of the hydroentangled nonwoven, in particular if it is crimped or pleated during manufacture of the segment for a smoking article. For such process steps, too great a thickness is disadvantageous and thicknesses in the preferred and particularly preferred intervals allow for a particularly good processability of the hydroentangled nonwoven according to the invention to form a segment of a smoking article.
The mechanical properties of the hydroentangled nonwoven are important for processing the hydroentangled nonwoven according to the invention into a segment of a smoking article. The tensile strength of the hydroentangled nonwoven with respect to width in the cross direction, measured in accordance with ISO 1924-2:2008, is preferably at least 0.05 kN/m and at most 5 kN/m, particularly preferably at least 0.07 kN/m and at most 4 kN/m.
The elongation at break of the hydroentangled nonwoven in the cross direction, measured in accordance with ISO 1924-2:2008 is thus preferably at least 0.5% and at most 50% and particularly preferably at least 0.8% and at most 40%. The elongation at break is primarily determined by the length of the fibers, wherein longer fibers lead to higher elongations at break, and it can therefore be adjusted to the specific requirements of the hydroentangled nonwoven within a wide range.
Segments according to the invention for smoking articles can be manufactured from the hydroentangled nonwoven according to the invention according to processes which are known in the art. These processes comprise, for example, crimping the hydroentangled nonwoven, forming a continuous tow from the crimped hydroentangled nonwoven, wrapping the continuous tow with a wrapper material and cutting the wrapped tow into individual rods of a defined length. In many cases, the length of such a rod is an integer multiple of the length of the segment that will then be used in the smoking article according to the invention, and therefore the rods are cut into segments of the desired length before or during manufacture of the smoking article.
The segment according to the invention for smoking articles comprises the hydroentangled nonwoven according to the invention and a wrapper material.
Specifically, the segment comprises a hydroentangled nonwoven gathered in the cross direction and a wrapper material, wherein the hydroentangled nonwoven contains at least 50% and at most 100% cellulose fibers, each with respect to the mass of the hydroentangled nonwoven. In this regard, the hydroentangled nonwoven has a basis weight of at least 15 g/m2 and at most 60 g/m2. For the determination of the basis weight, the area of the hydroentangled nonwoven is used as if it is spread out (i.e., no longer gathered). The hydroentangled nonwoven has a cross direction in which the hydroentangled nonwoven is gathered. In order to facilitate gathering of the hydroentangled nonwoven, it can be pre-formed by crimping or pleating. The term “gathering” should therefore be construed broadly, and the verb “gather” does not suggest any particular mechanical method by which the “gathered” state is achieved. Also, a “pleated” state is, for example, a “gathered” state in the context of the present disclosure, irrespectively of which mechanical way the pleating or shortening in the cross direction is achieved. Furthermore, in the non-gathered state, the hydroentangled nonwoven has a characteristic plastic deformability in the cross direction, which is characterized in that in a tensile test in the cross direction in accordance with ISO 1924-2:2008, the nonlinear portion of the deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break is at least 10% and at most 50% of the total deformation energy absorbed by the hydroentangled nonwoven up to half the elongation at break.
In a preferred embodiment of the segment according to the invention, the segment is cylindrical with a diameter of at least 3 mm and at most 10 mm, particularly preferably at least 4 mm and at most 9 mm and more particularly preferably at least 5 mm and at most 8 mm. These diameters are advantageous for using the segments according to the invention in smoking articles.
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 more particularly preferably at least 10 mm and at most 28 mm.
The draw resistance of the segment determines, inter alia, which pressure difference needs to be applied by the consumer during use of the smoking article in order to generate a certain volumetric flow through the smoking article, and it thus essentially influences the acceptance of the smoking article by the consumer. The draw resistance of the segment can be measured in accordance with ISO 6565:2015 and is given in mm water gauge (mmWG). To a very good approximation, the draw resistance of the segment is proportional to the length of the segment, so that the measurement of the draw resistance can also be carried out on rods that differ from the segment only in their length. The draw resistance of the segment can be easily calculated therefrom.
The draw resistance of the segment per unit length of the segment is preferably at least 1 mmWG/mm and at most 12 mmWG/mm and particularly preferably at least 2 mmWG/mm and at most 10 mmWG/mm.
The wrapper material of the segment according to the invention is preferably a paper or a film.
The wrapper material of the segment according to the invention preferably has a basis weight in accordance with ISO 536:2019 of at least 20 g/m2 and at most 150 g/m2, particularly preferably at least 30 g/m2 and at most 130 g/m2. A wrapper material with this preferred or particularly preferred basis weight provides the segment according to the invention wrapped therewith with a particularly advantageous hardness.
Smoking articles according to the invention can be manufactured from the segment according to the invention in accordance with processes which are known in the art.
The smoking article according to the invention comprises a segment that contains an aerosol-forming material and a segment that comprises the hydroentangled nonwoven according to the invention and a wrapper material.
As the cut surface of the segment according to the invention is optically very similar to that of a segment from cellulose acetate, in a preferred embodiment, the segment located next to the mouth end of the smoking article is a segment according to the invention.
In a preferred embodiment, the smoking article is a filter cigarette, and the aerosol-forming material comprises tobacco.
In a preferred embodiment, the smoking article is a smoking article, during the intended use of which the aerosol-forming material is only heated but not burned and the aerosol-forming material preferably comprises a material selected from the group consisting of tobacco, reconstituted tobacco, nicotine, glycerol, propylene glycol or mixtures thereof. Here, the aerosol-forming material can also be present in liquid form and can be located in a suitable container in the smoking article.
According to the findings of the inventors, the nonlinear portion of the deformation energy according to the invention can be achieved by orienting the fibers in the hydroentangled nonwoven more strongly in the machine direction of the hydroentangled nonwoven. This can be achieved by the process according to the invention described below.
The hydroentangled nonwoven according to the invention can be manufactured according to a process that comprises the steps A1 to A3.
In this regard, the steps A1 and A2 can be carried out such that the cellulose fibers in the finished hydroentangled nonwoven tend to be more oriented in the machine direction than in the cross direction.
The water jets directed onto the fiber web in step A2 cause an entanglement of the cellulose fibers, whereupon the structure conducive to the advantageous plastic behavior in the cross direction can be generated. Under “pressure of the water jet”, the skilled person will understand here the pressure which is applied to generate the water jet, for example, in a pressure chamber. According to the findings of the inventors, it is important for achieving an advantageous plastic behavior of the hydroentangled nonwoven that the proportion of the fibers oriented in the cross direction in the hydroentangled nonwoven is low and the fibers are oriented more in the machine direction and the thickness direction. In order to create this structure according to the invention in the hydroentangled nonwoven, the water jets should be arranged close to each other in the cross direction. Due to the proximity of the water jets hitting the fiber web simultaneously, the water spreads in the machine direction rather than in the cross direction and orients the fibers corresponding to this direction.
The pressure of the water jets can thereby be reduced compared to the commonly used pressure. The distance and the pressure of the water jets also substantially depends on the size of the openings, from which the water jets exit, and above all also on the speed of the fiber web, so that the skilled person can select the specific value according to experience, in consideration of the specific embodiments and by simple experiments.
In a preferred embodiment of the process according to the invention, a plurality of water jets is used to carry out the hydroentangling in step A2, wherein the water jets are arranged in at least one row transverse to the machine direction of the fiber web.
In a preferred embodiment of the process according to the invention, the hydroentangling in step A2 is carried out by at least two rows of water jets directed onto the fiber web, wherein particularly preferably, at least one row of water jets acts on each of the two sides of the fiber web.
In a preferred embodiment of the process according to the invention, the drying in step A3 is at least partially carried out by contact with hot air, by infra-red radiation or by microwave radiation. Drying by direct contact with a heated surface is also possible, but less preferred, because the thickness of the hydroentangled nonwoven could be reduced thereby.
The hydroentangled nonwoven manufactured according to this process should be suitable for use in segments for smoking articles. This means that it can in particular have all features, individually or in combination, that were described above in connection with the hydroentangled nonwoven and are defined in the dependent claims directed to the hydroentangled nonwoven.
In an advantageous embodiment said step A1 of providing the fiber web comprises the following steps B1 to B3:
In this embodiment of the process, the fiber web at least partially obtains the desired structure in that the speed at which the suspension in step B2 flows onto the running wire, and the speed of the running wire in step B2 are suitably adjusted relative to each other. In particular, according to the findings of the inventors, the speed at which the suspension in step B2 flows onto the running wire should be lower than the speed of the running wire. Due to the speed difference, the suspension is carried along with the wire and shearing forces are generated in the suspension which orient the cellulose fibers in the machine direction and thus contribute to a structure of the hydroentangled nonwoven that leads to the plastic deformability in the cross direction according to the invention. The skilled person can select the magnitude of the speed difference according to his experience and in consideration of the exemplary embodiments or by simple experiments. According to the experience of the inventors, a structure with the desired plastic deformability in the cross direction can be obtained in many cases if in step B2, the suspension is applied to the running wire at a speed that is only about 90% of the speed of the running wire, for example between 88% and 93% of the speed of the running wire. This value just serves as a reference point; a suitable numerical value for the speed difference will at least partially depend on the remaining process parameters and thus in practice, the skilled person will determine it experimentally, wherein the guiding principle and ultimately decisive criterion is the resulting characteristic plastic deformability in the cross direction of the hydroentangled nonwoven manufactured thereby, which, as described above, is characterized with reference to the tensile test in the cross direction in accordance with ISO 1924-2:2008.
In a preferred embodiment, the aqueous suspension in step B1 has a solids content of at most 3.0%, particularly preferably at most 1.0%, more particularly preferably at most 0.2% and in particular at most 0.05%. The particularly low solids content of the suspension enables a fiber web with a low density to be formed in step B3, which is advantageous for the filtration efficiency of a segment manufactured therefrom.
In a preferred embodiment, the running wire in steps B2 and B3 is inclined in the machine direction of the fiber web upwardly against the horizontal by an angle of at least 3º and at most 40°, particularly preferably by an angle of at least 5° and at most 30° and more particularly preferably by an angle of at least 15° and at most 25°.
In a preferred embodiment, the process comprises a step in which a pressure difference is applied between the two sides of the running wire to support the de-watering of the suspension in step B3, wherein particularly preferably, the pressure difference is generated by vacuum boxes or suitably shaped foils.
In a preferred embodiment, the process comprises a further step in which one or more additives are applied to the fiber web. The additives are preferably selected from the group consisting of alkyl ketene dimers (AKD), acid anhydrides such as alkenyl succinic acid anhydrides (ASA), polyvinyl alcohol, waxes, fatty acids, starch, starch derivative, carboxy methyl cellulose, alginates, chitosan, wet strength agents or substances for adjusting the pH such as, for example, organic or inorganic acids or bases and mixtures thereof. Alternatively or additionally, one or more additives can be applied which are selected from the group consisting of citrates such as trisodium citrate or tripotassium citrate, malates, tartrates, acetates such as sodium acetate or potassium acetate, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxalates, salicylates, α-hydroxy caprylates, phosphates, polyphosphates, chlorides and hydrogen carbonates, and mixtures thereof.
In a preferred embodiment, the application of the one additive or the additives is carried out between the steps A2 and A3 of the process according to the invention or after step A3, followed by a further step for drying the fiber web.
Some preferred embodiments of the hydroentangled nonwoven, of the process for manufacturing the hydroentangled nonwoven, of the segment for smoking articles and of the smoking article are described below. Further, a comparative example not according to the invention is described.
The device shown in
A suspension 31 from pulp fibers and fibers from regenerated cellulose was provided in a storage tank 32, step B1, and from there was pumped to a running wire 33, inclined upwards relative to the horizontal, step B2, and was de-watered by vacuum boxes 39, step B3, so that a fiber web 34 was formed on the wire, the general direction of movement of which is indicated by arrow 310. It should be noted that the steps B1 to B3 are specific sub-steps of the general process step A1 (providing a fiber web comprising cellulose fibers). In this regard, the speed at which the wire 33 moved was selected to be about 10% higher than the speed of the suspension 31 flowing from the storage tank 32, in order to orient the fibers primarily in the machine direction. The fiber web 34 was taken off the wire 33 and transferred to a support wire 35 which was also running, step C4. There, from devices 36, water jets 311 arranged in several rows transverse to the machine direction of the fiber web 34 were directed onto the fiber web 34 to entangle the fibers and to consolidate the fiber web 34 into a nonwoven, step A2. In continuation of step A2, water jets 312 were also directed onto the other side of the fiber web 34 by additional devices 37. Then, the still-moist nonwoven ran through a drying unit 38 and was dried there, step A3, to obtain the hydroentangled nonwoven.
To manufacture the hydroentangled nonwoven, a mixture of pulp fibers from coniferous woods and Lyocell® fibers was used, wherein the amount of fibers was selected such that the finished hydroentangled nonwoven consisted of 65% pulp fibers and 35% Lyocell® fibers. The finished hydroentangled nonwoven had a basis weight, in accordance with ISO 536:2019, of 55 g/m2.
In step A2 of the manufacturing process, firstly, water jets in three rows, 311 in
Samples were taken from these hydroentangled nonwovens in the cross direction and the force-elongation-diagram was recorded in a tensile test in accordance with ISO 1924-2:2008. The result is shown in
At the half elongation at break 8b/2, the corresponding force F(εb/2) is determined and the linear portion of the deformation energy Elin can be calculated therefrom by
The total deformation energy absorbed up to half the elongation at break corresponds to the area spanned by the x-axis 40 and curve C from ε=0 to ε=εb/2 and can be determined with sufficient accuracy without problems by methods of numerical integration. If the linear portion of the deformation energy Elin is subtracted therefrom, the hatched area remains, which corresponds to the nonlinear portion of the deformation energy Enl.
The determination of the deformation energies up to half the elongation at break was carried out for all three hydroentangled nonwovens A, B and C and the results are shown in Table 1, wherein E is the total deformation energy, Elin is the linear portion of the deformation energy, and Enl is the nonlinear portion of the deformation energy, each in the cross direction up to half the elongation at break. The deformation energies were determined numerically from the force-elongation-curves and thus formally have the unit N.%. In order to obtain the usual unit of J/m2, the sample geometry still needs to be considered. Since only the proportions relative to each other are important here and since the sample geometries are identical, this was not done. The elongation at break εb and the force at half the elongation at break F(εb/2) are also shown.
The values from Table 1 show that for the embodiments according to the invention A, B and C, the nonlinear portion of the deformation energy is about 20% to about 30%. It is also noticeable that with increasing pressure of the water jets, the elongation at break decreases. For this reason, it can be of advantage to select a lower pressure for the water jets, because apart from the good plastic elongation behavior, then larger permanent deformations are also possible during crimping.
Comparative example D related to the manufacture of a filter material in a process that only comprises the steps B1 to B3 and A3, but not the step for hydroentangling the fiber web. The filter material from Comparative Example D is therefore not according to the invention as it is not a hydroentangled nonwoven. Comparative Example D essentially serves to prove that the execution of steps B1 to B3 (as sub-steps of a preferred embodiment of the step A1) are in fact suitable for contributing to a structure that leads to a desired characteristic plastic deformability in the cross direction, if in step B2, the suspension is applied to the running wire at a reduced speed.
To manufacture the filter material, a mixture of pulp fibers from coniferous woods and Lyocell® fibers was used, wherein the amount of fibers was selected such that the finished filter material consisted of 80% pulp fibers and 20% Lyocell® fibers. The finished filter material had a basis weight, in accordance with ISO 536:2019, of 15 g/m2.
In step B2 of the process, the speed of the outflowing suspension was selected to be 10% lower than the speed of the running wire.
Four samples in the cross direction were taken from the filter material D obtained thereby and the force-elongation-diagram was recorded in a tensile test in accordance with ISO 1924-2:2008. The evaluation of the force-elongation-diagrams was carried out analogously to the embodiments A, B and C. The results of the four measurements are shown in Table 2.
The values from Table 2 show that the filter material D produced thereby has a nonlinear portion of the deformation energy of about 30% and that repeated measurements on the same sample material have a low variance. This proves that the steps B1 to B3 of the process indeed contribute to the desired plastic deformability in the cross direction, if the suspension in step B2 is applied to the running wire at reduced speed.
On the other hand, the special execution of step A1 (with reduced speed of application of the suspension in step B2) used in embodiments A, B and C is not needed in order to obtain the characteristic plastic deformability in the cross direction according to the invention in the hydroentangled nonwoven. This can be seen from embodiment E described below.
To manufacture the hydroentangled nonwoven in exemplary embodiment E, a mixture of pulp fibers from coniferous woods and Lyocell® fibers was used, wherein the amount of fibers was selected such that the finished hydroentangled nonwoven consisted of 80% pulp fibers and 20% Lyocell® fibers. Step A1 was carried out without firstly providing the pulp fibers in the fiber web with a preferred direction transverse to the machine direction by execution of step B2. The finished hydroentangled nonwoven had a basis weight, in accordance with ISO 536:2019, of 15 g/m2.
Step A2 for hydroentangling was carried out as in step A2 of exemplary embodiment B.
Two samples in the cross direction were taken from the hydroentangled nonwoven E obtained thereby and the force-elongation-diagram was recorded in a tensile test in accordance with ISO 1924-2:2008. The evaluation of the force-elongation-diagrams was carried out analogously to the embodiments A to C. The results of the two measurements are shown in Table 3.
The values from Table 3 show that the hydroentangled nonwoven E manufactured thereby has a proportion of the nonlinear deformation energy of about 17%. A comparison with exemplary embodiments A to C, which were manufactured by means of a combination of suitable execution of the hydroentangling in step A2 and pre-structuring the fiber web by reduced application speed in step B2 shows that this combination allows for higher portions of the nonlinear deformation energy of about 22% to about 28% and can therefore lead to a better performance during crimping. The outlay for the combined process is, of course, slightly higher than if, as in exemplary embodiment E, the characteristic plastic deformability in the cross direction according to the invention is only obtained by suitable execution of the hydroentangling in step A2. The exemplary embodiment E demonstrates that this is indeed possible.
To manufacture a filter material not according to the invention, the same mixture of fibers was used as in exemplary embodiment D. The basis weight was still 15 g/m2, but only machine settings that are common for manufacturing filter papers were used.
Three samples in the cross direction were taken from the filter material of comparative example Z and the force-elongation-diagram was recorded in a tensile test in accordance with ISO 1924-2:2008. The evaluation of the force-elongation-diagrams was carried out analogously to the embodiments A to C. The results of the three measurements are shown in Table 4.
The force-elongation-curves of comparative example Z are shown in
Filter rods wrapped with paper with a length of 100 mm and a diameter of 7.85 mm were manufactured from each hydroentangled nonwoven of exemplary embodiments A to E and the filter material of comparative example Z. The width of the hydroentangled nonwoven and the machine settings during filter manufacturing were selected such that a draw resistance of 450±10 mmWG resulted.
Filter rods could be manufactured from the hydroentangled nonwovens of exemplary embodiments A to C and E and the filter material of comparative example Z. However, during manufacture, it was found that for the hydroentangled nonwovens of exemplary embodiments A to C and E, the process of crimping reacted substantially less sensitively to changes in the machine settings and in particular to the setting of the distance between the rolls during crimping than for comparative example Z.
Filter cigarettes were manufactured from the segments of the exemplary embodiments A to C and E and the comparative example Z according to a common process from the prior art. This manufacturing process was without any problems.
Thus, it can be seen that segments and smoking articles can be manufactured from the hydroentangled nonwoven according to the invention more reliably and more easily than from common hydroentangled nonwovens or papers, and that better results can be achieved during crimping due to the advantageous plastic elongation behavior.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/066102 | 6/15/2021 | WO |
