DE102020119388A1 - PLEATED FILTER MATERIAL FOR SMOKING ARTICLES - Google Patents

Abstract

Shown is a filter material for manufacturing a segment for a smoking article, wherein the filter material comprises a hydroentangled nonwoven, and the nonwoven comprises fibers, wherein the fibers are selected from the group consisting of wood pulp fibers, fibers made of regenerated cellulose and mixtures thereof, and these fibers together are contained in the nonwoven in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven, and wherein the nonwoven is web-shaped, a longitudinal direction in the running direction of the web, a transverse direction orthogonal thereto in the plane of the web and a transverse direction orthogonal to the longitudinal direction and transverse direction Has thickness direction. The nonwoven fabric is shaped in such a way that it has a wave structure with a wave height of at least 50 µm and at most 1000 µm and a wavelength of at least 150 µm and at most 5000 µm in the plane spanned by the transverse direction and thickness direction.

Description

FIELD OF THE INVENTION

The invention relates to a filter material suitable for the manufacture of a segment in a smoking article which is pleated and from which segments for smoking articles can be manufactured in an efficient manner. The invention also relates to a segment for a smoking article made from this filter material.

BACKGROUND AND PRIOR ART

Smoking articles are typically rod-shaped articles consisting of at least two rod-shaped segments arranged one after the other. One segment contains a material that is capable of forming an aerosol when heated, and at least one other segment is used 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 a further segment is designed as a filter and is used to filter the aerosol. The aerosol is generated by burning the aerosol-forming material, and the filter primarily serves to filter the aerosol and to provide the filter cigarette with a defined draw resistance.

However, the smoking article can also be a so-called tobacco heater, in which the aerosol-forming material is only heated but not burned. This reduces the number and amount of harmful substances in the aerosol. Such a smoking article also consists of at least two, but more often more, in particular four segments. One segment contains the aerosol forming material, which typically comprises tobacco, reconstituted tobacco, or tobacco processed by other processes. Other segments in the smoking article, some of which are optional, are used to direct the aerosol, cool the aerosol or filter the aerosol.

The segments are mostly encased by an encasing material. Paper is very often used as a wrapping material.

In the following, unless explicitly stated otherwise or the context indicates otherwise, the term “segment” is understood to mean the segment of a smoking article that does not contain the aerosol-forming material but is used, for example, to convey, cool or filter the aerosol.

Forming such segments from polymers such as cellulose acetate or polylactides is known from the prior art. After consumption of the smoking article, the smoking article must be disposed of appropriately. In many cases, however, the consumer simply throws the consumed smoking article away in the environment and attempts to restrict this behavior through information or punishment have had little success.

Since cellulose acetate and polylactides only biodegrade very slowly in the environment, paper and cellulose-based nonwovens have gained in importance. In the manufacture of a segment, a web of paper or a cellulose-based fleece is first pleated in the longitudinal direction, then formed into an endless strand and wrapped with a wrapping material. Finally, the endless strand is cut into pieces suitable for further processing.

In pleating the web, the web is passed through two patterned rollers which, under high pressure, emboss that pattern onto the web. Typically, this pattern is a line pattern oriented in the machine direction of the web. The embossed lines weaken the web in the direction orthogonal to the running direction, the cross direction, so that an endless strand can then be formed more easily by pushing the web together in the cross direction.

When pleating, however, it happens that the web is cut lengthwise due to the considerable pressure of the rollers and tears off during further processing or causes other technical problems. There is therefore a need for a filter material which does not have this disadvantage or only has it to a lesser extent, but which is otherwise as identical as possible to the known filter materials.

SUMMARY OF THE INVENTION

The invention is based on the object of providing a filter material for a smoking article which can be processed with high productivity into a segment of a smoking article and which is otherwise as similar as possible to conventional filter materials in terms of its properties.

This object is achieved by a filter material according to claim 1, a segment of a smoking article according to claim 17, and a smoking article according to claim 24, and by a method for producing the filter material according to claim 27. Advantageous developments are specified in the dependent claims.

The inventors have found that this object can be achieved by a filter material for producing a segment for a smoking article, the filter material comprising a hydroentangled nonwoven, and the nonwoven comprising fibers, the fibers being selected from the group consisting of cellulose fibers, fibers from regenerated cellulose and mixtures thereof, and these fibers are contained together in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric in the nonwoven fabric, and wherein the nonwoven fabric is in the form of a web, one longitudinal direction in the running direction of the web, one orthogonal thereto in the has a transverse direction lying in the plane of the web and a thickness direction orthogonal to the longitudinal direction and transverse direction and is shaped in such a way that the nonwoven fabric has a corrugated structure in the plane defined by the transverse direction and thickness direction with a corrugation height of at least 50 µm and a maximum of 1000 µm, and a wavelength of at least at least 150 µm and at most 5000 µm.

Although the term "hydroentangled" initially refers to the underlying manufacturing process, it should be noted that a hydroentangled nonwoven fabric has characteristic structural properties that distinguish it from other nonwoven fabrics and which, to the inventors' knowledge, cannot be achieved in an identical manner by a different manufacturing process . In contrast to paper, for example, where the strength is mainly caused by hydrogen bonds and the fibers are mainly arranged in the plane of the paper, the strength of the hydroentangled nonwoven is achieved by the turbulence of the fibers and as a result the fibers are to a significant extent also aligned in the thickness direction of the non-woven fabric.

In the production of the hydroentangled nonwoven fabric of the present invention, fibers are placed on a water-permeable screen and entangled by turbulence with a plurality of transverse water jets directed at the fibers. Through the special selection of the arrangement and the properties of the water jets, according to the invention, a wavy structure can be produced in the transverse direction in the nonwoven fabric, which is similar to a structure that can also be obtained by pleating. The non-woven fabric and the filter material according to the invention comprising the non-woven fabric are therefore pre-pleated.

In the manufacture of a continuous strand from the filter material of the present invention, the filter material is passed through two patterned rollers. Due to the fact that the filter material according to the invention is already pre-pleated, however, only a considerably lower pressure is required to achieve sufficient pleating of the filter material, or pleating can even be dispensed with entirely. This also significantly reduces the likelihood of accidentally cutting the filter material lengthwise. In this way, the number of operational interruptions in the production of the endless strand and the segments can be reduced and productivity is increased, which represents the essential advantage of the filter material according to the invention.

The nonwoven fabric is in the form of a web and has a longitudinal direction in the running direction of the web and a direction orthogonal thereto in the plane of the web, which is referred to as the transverse direction. The direction orthogonal to the longitudinal and transverse directions is referred to as the thickness direction. The nonwoven fabric contained in the filter material according to the invention has a corrugated structure in the plane formed by the transverse direction and the thickness direction, the cross-sectional area, with the wavelength extending essentially in the transverse direction and the wave height essentially extending in the thickness direction. According to the invention, the wave height is at least 50 μm and at most 1000 μm, preferably at least 100 μm and at most 900 μm and particularly preferably at least 150 μm and at most 800 μm. According to the invention, the wavelength is at least 150 μm and at most 5000 μm, preferably at least 300 μm and at most 4000 μm and particularly preferably at least 500 μm and at most 2000 μm.

The shape of the corrugated structure is not particularly important, but it must be strong enough so that the non-woven fabric can be pushed together more easily in the transverse direction than with the same non-woven fabric without a corrugated structure. Due to the manufacturing process, the wave height and wavelength can also vary significantly within a cross-sectional area. This is not important for the inventive effect as long as the wavelength and the wave height are in the specified intervals over a large part of the cross-sectional area, in particular over at least 60%, preferably at least 75% of the cross-sectional area.

The corrugated structure does not have to be pronounced on the top and bottom of the non-woven fabric, it is sufficient if it is pronounced on one side, since the resulting thin areas in the troughs of the waves also make it easier to push the non-woven fabric together in the transverse direction and thus the necessary pressure reduce when pleating during manufacture of the segment.

The roughness of the surface alone is generally not sufficient to achieve the inventive effect.

The corrugated structure of the non-woven fabric can be determined by embedding a sample of the non-woven fabric in a suitable epoxy resin. After the epoxy has cured, the sample can be ground in the cross-sectional plane of the non-woven fabric or cut through a microtome so that the cross-sectional area is visible under a light microscope. With a light microscope, the wave structure can be made visible and the wave height and wavelength can be measured. A camera connected to the light microscope can be used to create images of sections of the cross-sectional area.

The specified conditions with regard to wave height and wavelength are sufficiently met for the invention if they are met in representative sections of a cross-sectional area. Due to the manufacturing process, the wave structure generally changes only insignificantly in the longitudinal direction of the nonwoven, so that it is not necessary to carry out such a measurement on several cross-sectional areas in the longitudinal direction to check the requirements for wave height and wavelength.

A scanning electron microscope can also be used as an alternative to a light microscope.

For a favorable tensile strength and to adjust the tensile strength or filtration efficiency of a segment made from the filter material according to the invention, the hydroentangled nonwoven contains cellulose fibers, fibers made from regenerated cellulose or a mixture thereof in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven. The amount of these fibers is preferably at least 60% and at most 95%, in each case based on the mass of the hydroentangled nonwoven.

The cellulose fibers can preferably be obtained from conifers, deciduous trees or other plants such as hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, cotton or esparto grass. Mixtures of cellulose fibers from different origins can also be used. The cellulose fibers are particularly preferably obtained from coniferous woods, for example from spruce, pine or fir, because these fibers lead to good strength of the hydroentangled nonwoven fabric due to their length. Pulp obtained from softwoods, which is referred to as reinforced pulp and achieves particularly high strength, and mercerized cellulose, which achieves particularly high thickness and low density, are very particularly preferred.

The pulp fibers can be bleached or unbleached. Bleached cellulose fibers offer advantages in the appearance of a segment made from the filter material according to the invention because of their white color, while unbleached cellulose fibers, which then have a light brown to dark brown color, are more environmentally friendly because the bleaching process can be omitted. Mixtures of bleached and unbleached cellulose fibers can also be used to better adjust the color of the filter material according to the invention.

The fibers made from regenerated cellulose are preferably viscose fibers, modal fibers, Lyocell®, Tencel® or mixtures thereof. These fibers have good biodegradability and can be used to optimize the strength, thickness or density of the hydroentangled nonwoven fabric and adjust the filtration efficiency of the resulting smoking article segment.

In a very particularly preferred embodiment, the filter material according to the invention comprises a hydroentangled nonwoven fabric which consists essentially exclusively, but at least to at least 95% of the mass of the hydroentangled nonwoven fabric of cellulose fibers, fibers of regenerated cellulose or a mixture thereof. This very particularly preferred embodiment permits very good biodegradability and rapid disintegration on contact with water, while at the same time having a very small impact on the taste of the smoking article made with the help of the filter material.

In a preferred embodiment of the filter material according to the invention, the hydroentangled nonwoven of the filter material contains at least 5% and less than 50%, more preferably less than 40% and very particularly preferably less than 30% staple fibers made of cellulose acetate, the percentages based on the mass of the hydroentangled nonwoven relate.

Additives such as alkyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA), fatty acids, starch, starch derivatives, carboxymethyl cellulose, alginates, or substances for adjusting the pH, such as organic or inorganic acids and salts thereof or alkalis can be used to adjust specific properties of the nonwoven to be added. The person skilled in the art is able to determine the type and amount of such additives from his experience.

The basis weight of the hydroentangled nonwoven is preferably at least 25 g/m ² and at most 150 g/m ² , more preferably at least 35 g/m ² and at most 120 g/m ² and most preferably at least 40 g/m ² and at most 100 g/m ² . The basis weight affects the tensile strength of the hydroentangled nonwoven fabric, with a higher basis weight leading to higher strength.

The thickness of the hydroentangled nonwoven is preferably at least 100 μm and at most 1000 μm, particularly preferably at least 120 μm and at most 800 μm and very particularly preferably at least 150 μm and at most 750 μm. The thickness affects the amount of filter material that can be packed into the segment of the smoking article and thus the draw resistance and filtration efficiency of the segment, but also the processability of the filter material, since a high thickness makes it difficult to pleat the filter material. Due to the corrugated structure of the non-woven fabric, the filter material according to the invention allows a greater thickness without problems arising during pleating. A filter material according to the invention can therefore be used particularly well if segments with high density and high draw resistance are to be produced. The thickness measurement is influenced by the corrugated structure of the material. However, this fact is ignored when specifying the thickness, because the thickness measured in this way also serves as a measure of how much filter material can be rolled up on a roll with a given diameter. Thickness can be measured according to EDANA Standard Procedure NWSP 120.6.R0 (15).

The density of the hydroentangled nonwoven is obtained by dividing the basis weight by the thickness. The density of the hydroentangled nonwoven is preferably at least 50 kg/m ³ and at most 300 kg/m ³ , particularly preferably at least 70 kg/m ³ and at most 250 kg/m ³ and very particularly preferably at least 80 kg/m ³ and at most 220 kg / ^m3 . These values relate to the density before a segment of a smoking article is manufactured from the filter material according to the invention comprising this hydroentangled nonwoven fabric. The density of the hydroentangled nonwoven determines, among other things, the draw resistance and the filtration efficiency of the segment of a smoking article made from it. The preferred intervals allow for a favorable combination of draw resistance and filtration efficiency.

The mechanical properties of the hydroentangled nonwoven are important for the processing of the filter material according to the invention into a segment for a smoking article. The width-related tensile strength of the hydroentangled nonwoven 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 is important because the filter material is pleated during the processing of the filter material according to the invention to form a segment of a smoking article, and a particularly high elongation at break is favorable. The corrugated structure of the non-woven material allows a particularly high elongation at break in the transverse direction and facilitates pleating when manufacturing the segment. The elongation at break in the transverse direction of the hydroentangled nonwoven fabric is preferably at least 1% and at most 50% and particularly preferably at least 3% and at most 40%.

Tensile strength and elongation at break can depend on the direction in which the sample for measurement was taken from the hydroentangled nonwoven fabric. The requirements for the tensile strength of the hydroentangled nonwoven are met if the tensile strength in at least one direction is within the specified preferred or particularly preferred intervals. The elongation at break is given in the transverse direction and must be measured.

The filter material according to the invention comprises the hydroentangled nonwoven. Preferably, however, the hydroentangled nonwoven makes up the majority of the filter material, so that preferably at least 80% of the mass of the filter material is formed by the hydroentangled nonwoven and particularly preferably at least 90% of the mass of the filter material is formed by the hydroentangled nonwoven.

In addition to the hydroentangled nonwoven, the filter material according to the invention can also comprise other components which, for example, influence the processability of the filter material or the properties of a segment made from it or the taste of the smoking article. These include, for example, impregnation of the nonwoven with flavorings, carriers of flavorings, in particular threads impregnated with flavorings or substances to increase the rigidity of the filter material or materials that increase the hardness of the filter made from the filter material.

In a preferred embodiment of the filter material according to the invention, the filter material comprises the hydroentangled nonwoven and one or more substances selected from the group consisting of triacetin, glycol, propylene glycol, sorbitol, glycerol, polyethylene glycol, polyvinyl alcohol and triethyl citrate or mixtures thereof. These substances can help the Filtra tion efficiency to better adapt to that of cellulose acetate.

If at least 90% of the mass of the filter material is formed by the hydroentangled nonwoven, the fulfillment of the above-mentioned characteristics of the hydroentangled nonwoven, for example with regard to the content of cellulose fibers, the content of fibers from regenerated cellulose, the density, the thickness, the basis weight, the Tensile strength and elongation at break can also be tested on the filter material itself, without the hydroentangled nonwoven having to be isolated from the filter material. The above-mentioned preferred, particularly preferred and very particularly preferred intervals and properties according to the invention then also apply to the filter material made from the hydroentangled nonwoven.

Segments according to the invention for smoking articles can be produced from the filter material according to the invention by methods known from the prior art. These methods include, for example, pleating the filter material, forming a continuous strand from the pleated filter material, wrapping the continuous strand with a wrapping material, and cutting the wrapped strand 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 then to be used in the smoking article of the invention and therefore the rods are then cut into segments of the desired length before or during manufacture of the smoking article.

The segment for smoking articles according to the invention comprises the filter material according to the invention and a wrapping material.

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 very particularly preferably at least 5 mm and at most 8 mm. These diameters are favorable 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 very particularly preferably at least 10 mm and at most 28 mm.

The draw resistance of the segment determines, among other things, what pressure difference the smoker has to apply when consuming the smoking article in order to generate a specific volume flow through the smoking article, and it therefore significantly influences the smoker's acceptance of the smoking article. The draw resistance of the segment can be measured according to ISO 6565:2015 and is given in mm water column (mmWG). In a very good approximation, the tensile resistance of the segment is proportional to the length of the segment, so that the tensile resistance can also be measured on rods that differ from the segment only in length. From this, the drag resistance of the segment can be easily calculated.

The tensile resistance of the segment per 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 covering material of the segment according to the invention is preferably paper or foil.

The covering material of the segment according to the invention preferably has a basis weight of at least 20 g/m ² and at most 150 g/m ² , particularly preferably at least 30 g/m ² and at most 130 g/m ² . A covering material with this preferred or particularly preferred weight per unit area gives the segment according to the invention covered therewith a particularly advantageous hardness. This prevents the smoker from accidentally squeezing the segment located in the smoking article.

In a preferred embodiment, the segment according to the invention additionally contains at least one capsule containing flavorings. The capsule is often designed in such a way that the smoker can break it by applying pressure with his fingers, thereby releasing the flavorings so that they can change the taste of the smoking article.

Smoking articles according to the invention can be produced from the segment according to the invention by methods known in the prior art.

The smoking article of the present invention comprises a segment containing an aerosol forming material and a segment comprising the filter material of the present invention and a wrapper material.

In a preferred embodiment, the smoking article is a filter cigarette and the aerosol forming material is tobacco.

In a preferred embodiment, the smoking article is a smoking article in which certain intended use, the aerosol-forming material is only heated but not burned.

1. A - Bereitstellen einer Faserbahn umfassend Fasern, ausgewählt aus der Gruppe bestehend aus Zellstofffasern, Fasern aus regenerierter Cellulose und Mischungen daraus,
2. B - Wasserstrahlverfestigen der Faserbahn durch eine Vielzahl von auf die Faserbahn gerichteten Wasserstrahlen,
3. C - Erzeugen einer Wellenstruktur im Vliesstoff durch eine Vielzahl von auf die Faserbahn gerichteten Wasserstrahlen,
4. D - Trocknen des wasserstrahlverfestigten Vliesstoffs,

wobei der Anteil der genannten Fasern in der Faserbahn von Schritt A so gewählt ist, dass diese Fasern insgesamt in einer Menge von mindestens 50% und höchstens 100% der Masse des wasserstrahlverfestigten Vliesstoffs im getrockneten Zustand von Schritt D enthalten sind, wobei die in Schritt A bereitgestellte Faserbahn eine Längsrichtung in Laufrichtung der Faserbahn, eine dazu orthogonale in der Faserbahnebene liegende Querrichtung und eine zu Längsrichtung und Querrichtung orthogonale Dickenrichtung aufweist, und die auf die Faserbahn gerichteten Wasserstrahlen in Schritt C so angeordnet sind, dass sie in Querrichtung jeweils von Mittelpunkt zu Mittelpunkt des Wasserstrahls beim Auftritt auf die Faserbahn einen Abstand voneinander von mindestens 150 µm und höchstens 5000 µm aufweisen und der Druck jedes Wasserstrahls in Schritt C mindestens 2 MPa und höchstens 70 MPa beträgt, und der in Schritt D erhaltene Vliesstoff in der aus Querrichtung und Dickenrichtung aufgespannten Ebene eine Wellenstruktur mit einer Wellenhöhe von mindestens 50 µm und höchstens 1000 µm, sowie eine Wellenlänge von mindestens 150 µm und höchstens 5000 µm aufweist. Hierbei und im Rest der vorliegenden Offenbarung bezeichnet der „Druck eines Wasserstrahls“ in üblicher Weise den Druck in einer Druckkammer, der zur Erzeugung des Wasserstrahls aufgewendet wird.The hydroentangled nonwoven fabric for the filter material according to the invention can be produced by the following method according to the invention, which comprises the following steps A to D.

1. A - providing a fibrous web comprising fibers selected from the group consisting of cellulose fibers, regenerated cellulose fibers and mixtures thereof,
2. B - hydroentanglement of the fibrous web by a plurality of water jets directed at the fibrous web,
3. C - creating a wavy structure in the non-woven fabric by means of a large number of water jets directed at the fibrous web,
4. D - drying the hydroentangled nonwoven fabric,

wherein the proportion of said fibers in the fibrous web of step A is selected such that these fibers are contained in total in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric in the dried state of step D, wherein the in step A provided fibrous web has a longitudinal direction in the running direction of the fibrous web, a transverse direction orthogonal thereto in the plane of the fibrous web, and a thickness direction orthogonal to the longitudinal direction and transverse direction, and the water jets directed onto the fibrous web are arranged in step C such that they are in the transverse direction from center to center of the water jets having a distance from each other of at least 150 µm and at most 5000 µm when hitting the fibrous web, and the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven fabric obtained in step D in the stretched from the transverse direction and the thickness direction level one Wave structure with a wave height of at least 50 µm and at most 1000 µm, and a wavelength of at least 150 µm and at most 5000 µm. As used herein and throughout the rest of this disclosure, “water jet pressure” commonly refers to the pressure in a pressure chamber used to generate the water jet.

According to the findings of the inventors, a water jet at a correspondingly high pressure is suitable for producing a depression in the nonwoven fabric passing under the water jet, which depression can be perceived as a wave trough in the cross-sectional area. A pressure of at least 2 MPa is required for this, although the pressure depends very significantly on the speed at which the fiber web runs through the device. At higher speeds, higher pressure is required. Due to this correspondingly high pressure, the fibers are not only swirled, but also partially displaced, which contributes significantly to the formation of the wave structure. During treatment with water jets, the fibrous web is typically supported by a wire and the structure of the wire should also preferably be chosen to be suitable for the intended corrugated structure, since the fibers are mainly displaced to where the wire is permeable.

In the prior art, the water jets are not arranged in defined positions with respect to the fiber web when water-jet bonding a nonwoven fabric, but in such a way that uniform bonding by the water jets can be achieved over the entire surface of the fiber web passing through. However, even if the pressure of the water jets exceeds 2 MPa, this does not lead to a wave structure as is characteristic of the filter material according to the invention.

According to the invention, the water jets used to generate the wave structure must therefore be arranged accordingly, in particular in such a way that high-pressure water jets are not directed at locations on the fiber web where a wave crest is to be generated. The water jets, which are intended to produce the corrugated structure in step C, are therefore offset in the transverse direction and have a distance from one another in the transverse direction from center to center of the water jets at the point where they occur on the fibrous web of at least 150 µm and at most 5000 µm. These water jets may be arranged in any longitudinal direction.

It is also possible to direct water jets to both sides of the fibrous web to carry out step B or C. The water jets in step C are preferably arranged in such a way that they hit points that are intended to form wave troughs when viewed from the respective side.

The pressure of the water jets, which serve to strengthen the nonwoven fabric in step B, can also exceed 2 MPa and can also be selected to be significantly higher, particularly at higher speeds of the fiber web. According to the invention, it is only important that the effect of all the water jets together is not distributed so evenly over the surface of the fibrous web that no wavy structure can arise.

According to the invention, a water jet to produce the corrugated structure in step C requires a pressure of at least 2 MPa and at most 70 MPa. According to the inventors' knowledge, at a pressure of less than 2 MPa, no embossed corrugated structure can be generated and at a pressure of over 70 MPa there is a risk of cutting the fiber web even at higher speeds. The pressure of the water jets in step C is preferably at least 3 MPa and at most 40 MPa. The pressure for generating the corrugated structure can be selected as a function of the running speed of the fibrous web, so that the ratio p/v of the pressure p in MPa and the running speed v of the fibrous web in m/s is preferably selected such that 2.5≦ p/v ≤ 20 and more preferably 3 ≤ p/v ≤ 15.

The water jets in step C preferably emerge from an opening which has an area of at least 450 μm ² and at most 50,000 μm ² and is particularly preferably a circular opening.

The pressure of the water jets in step B is preferably at least 0.5 MPa and at most 60 MPa, more preferably at least 1 MPa and at most 50 MPa, with high pressure being combined above all with high speeds of the fibrous web in order to prevent the fibrous web from being cut up . The pressure for solidifying the fibrous web can be selected as a function of the running speed of the fibrous web, so that the ratio p/v from the pressure p in MPa and the running speed v of the fibrous web in m/s is preferably selected such that 2≦p/ v ≤ 10 and more preferably 4 ≤ p/v ≤ 8.

The wave structure is characterized by the wave height and wavelength that can be seen in the cross-sectional area of the nonwoven. According to the invention, the wave height after step D is at least 50 μm and at most 1000 μm, preferably at least 100 μm and at most 900 μm and particularly preferably at least 150 μm and at most 800 μm. According to the invention, the wavelength after step D is at least 150 μm and at most 5000 μm, preferably at least 300 μm and at most 4000 μm and particularly preferably at least 500 μm and at most 2000 μm.

The hydroentangled nonwoven produced by this process is said to be suitable for use in the filter material described above. This means that it can in particular have all the features, individually or in combination, which have been described above in connection with the hydroentangled nonwoven fabric as a component of the filter material and are defined in the claims directed to the filter material.

The fibrous web can be provided in step A by various methods, for example by a wet-laid method or a dry-laid method (airlaid).

• A1.1 - Herstellen einer wässrigen Suspension umfassend Fasern, ausgewählt aus der Gruppe bestehend aus Zellstofffasern, Fasern aus regenerierter Cellulose und Mischungen daraus, wobei die Menge an diesen Fasern so gewählt ist, dass diese Fasern insgesamt in einer Menge von mindestens 50% und höchstens 100% der Masse des wasserstrahlverfestigten Vliesstoffs im getrockneten Zustand von Schritt D enthalten sind,
• A1.2 - Aufbringen der Suspension aus Schritt A1.1 auf ein umlaufendes Sieb,
• A1.3 - Entwässern der Suspension durch das umlaufende Sieb, um eine Faserbahn zu bilden, und besonders bevorzugt umfassend einen weiteren Teilschritt A1.4,
• A1.4 - Einstellen des Feuchtegehalts der Faserbahn durch Trocknen oder Befeuchten.

In a preferred variant A1 of the method according to the invention, the fibrous web is provided in step A by a wet-laid method comprising the sub-steps A1.1 to A1.3,

• A1.1 - Preparation of an aqueous suspension comprising fibers selected from the group consisting of cellulose fibers, regenerated cellulose fibers and mixtures thereof, the amount of these fibers being selected such that these fibers in total are present in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric are contained in the dried state of step D,
• A1.2 - applying the suspension from step A1.1 to a rotating screen,
• A1.3 - dewatering of the suspension through the circulating wire to form a fibrous web, and particularly preferably comprising a further sub-step A1.4,
• A1.4 - Adjusting the moisture content of the fibrous web by drying or moistening.

In a preferred embodiment of variant A1 of the method according to the invention, the aqueous suspension in step A1.1 has a solids content of at least 0.005% and at most 3.0%, particularly preferably at least 0.005% and at most 1.0%, very particularly preferably at least 0. 01% and at most 0.2% and in particular at least 0.01% and at most 0.05%. The particularly low solids content of the suspension makes it possible to form an even less dense fibrous web in step A1.3.

In a preferred embodiment of variant A1 of the method according to the invention, the circulating screen of steps A1.2 and A1.3 is at an angle of at least 3° and at most 40° to the horizontal in the direction of travel of the fibrous web, particularly preferably at an angle of at least 5 ° and at most 30° and most preferably at an angle of at least 15° and at most 25° upwards.

In a preferred embodiment of variant A1 of the method according to the invention, dewatering is supported in step A1.3 by generating a pressure difference between the two sides of the rotating screen, with the pressure difference being particularly preferably generated by vacuum boxes or suitably shaped blades.

In a preferred embodiment of variant A1 of the method according to the invention, the drying in step A1.4 is carried out by heated Drying cylinder or by hot air and moistening by a spray bar. The drying process and the subsequent moistening serve to optimally adjust the moisture content of the fibrous web for the hydroentanglement in step B. In particular, in step A1.4, the fibrous web can first be dried approximately to the equilibrium moisture content at normal room temperature and humidity, after which the fibrous web is rolled up, transported to a separate device that carries out the hydroentanglement, unrolled there and the moisture content for the following step B.

• A2.1 - Herstellen einer Faserbahn durch ein Trockenlegeverfahren („air-laid“), wobei die Faserbahn Fasern umfasst, die ausgewählt sind aus der Gruppe bestehend aus Zellstofffasern, Fasern aus regenerierter Cellulose und Mischungen daraus, wobei die Menge an diesen Fasern so gewählt ist, dass diese Fasern insgesamt in einer Menge von mindestens 50% und höchstens 100% der Masse des wasserstrahlverfestigten Vliesstoffs im getrockneten Zustand von Schritt D enthalten sind, und
• A2.2 - Befeuchten der Faserbahn.

In a preferred variant A2 of the method according to the invention, the fibrous web is provided in step A by means of a dry laying method (“air-laid”) comprising the sub-steps A2.1 and A2.2,

• A2.1 - Manufacture of a fibrous web by an air-laid process, the fibrous web comprising fibers selected from the group consisting of wood pulp fibers, regenerated cellulose fibers and mixtures thereof, the amount of these fibers being so selected is that these fibers are contained in total in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric in the dried state of step D, and
• A2.2 - Moistening the fibrous web.

Such a dry laying method of variant A2 can bring advantages because, for example, the energy-intensive drying in step A1.4 of variant A1 can be omitted.

In a preferred embodiment of the method according to the invention, the drying in step D is effected at least partially by contact with hot air, by infrared radiation or by microwave radiation. In a very particularly preferred embodiment of the process according to the invention, the drying in step D is carried out by through-flow drying. With this through-air drying, which is also referred to in the technical field as “through-air drying” (TAD), the fiber material is dried by forcing a warm gas stream, in particular an air stream, through the fiber material. With through-air drying, the best quality of the hydroentangled nonwoven can be achieved. Drying by direct contact with a heated surface is also possible, but less preferred because the corrugated structure of the hydroentangled nonwoven can be destroyed.

character list

• 1 shows a device by means of which the method according to the invention for the production of the hydroentangled nonwoven can be carried out.
• 2 shows an example of the determination of the wave height and wavelength of the wave structure of the nonwoven
• 3 shows the cross-sectional area of the nonwoven for a filter material according to the invention
• 4 shows the cross-sectional area of a filter material not according to the invention after pleating

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some preferred embodiments of the filter material and the method for the production of the hydroentangled nonwoven fabric are described below.

The method described below was used to produce the hydroentangled nonwoven fabric, which is contained in the filter material according to the invention, in which the 1 device shown schematically was used.

An aqueous suspension 1 of pulp fibers and fibers from regenerated cellulose was pumped from a storage tank 2 onto a revolving screen 3 inclined upwards to the horizontal and dewatered by vacuum boxes 9 so that a fibrous web 4 formed on the screen, the general direction of movement of which is indicated by the arrow 10 is indicated. The fiber web 4 was removed from the screen 3 and transferred to a supporting screen 5 which is also rotating. If necessary, this transfer can be simplified by a suction roll (so-called "pick up roll") or by solidifying the fiber web using water jets before transfer. Water jets 11 arranged in three rows in the transverse direction to the fibrous web 4 were directed onto the fibrous web 4 from devices 6 on the supporting wire 5 in order to entangle the fibers and solidify the fibrous web 4 into a nonwoven fabric. In a further step, water jets 12 with a higher pressure were directed onto the fiber web 4 by additional devices 7 in order to produce the wave structure explained above. Unlike the devices 6, the devices 7 were adjusted in such a way that the water jets 12 of the two longitudinally consecutive rows were directed as far as possible to the same position in the transverse direction. As a result, the water jets 12 seen in the running direction of the second row were directed to the wave troughs generated by the water jets 12 of the first row and thus reinforced those of wave structure generated in the first row. Optional devices 6a can direct further water jets 11a onto the fibrous web, whereby these water jets, depending on the arrangement and pressure, can serve both to solidify the nonwoven fabric and to produce or reinforce the corrugated structure. Deviating from the representation in 1 the water jets of the devices 6a can also be directed onto the fibrous web 4 from the same side as the water jets 11 or 12. The nonwoven fabric, which was still moist, then passed through a through-air drying 8 and was dried there.

A mixture of 80% by weight cellulose fibers and 20% by weight Lyocell® fibers was used to produce the hydroentangled nonwoven fabric. The fibers were consolidated by three series of water jets 11 generated at a pressure of 3 MPa, 5 MPa and 6 MPa, relative to the running direction. The corrugated structure of the non-woven fabric was effected by two rows of water jets 12 generated in both rows with a pressure of 8.5 MPa. The devices 7 for generating the water jets 12 were arranged in both rows in the transverse direction at a distance of 2000 μm and had a diameter of 100 μm. The speed of the fibrous web was 50 m/min, which is relatively low. At higher speeds, the pressures of the water jets 11 and 12 must be increased accordingly. Values of 3/(50/60) = 3.6 to 6/(50/ 60) = 7.2. To produce the wave structure, the ratio p/v from the pressure p of the water jets in MPa and the running speed of the fiber web in m/s is 8.5/(50/60)=10.2.

The weight per unit area of the nonwoven produced in this way was determined as 49.6 g/m ² , the thickness according to NWSP 120.6.R0 (15) as 522 μm and the density as 95 kg/m ³ . The tensile strength in the longitudinal direction was 8.6 N/15 mm, the elongation at break in the transverse direction was 31%.

A sample of the non-woven fabric was embedded in epoxy resin, and after the epoxy resin had hardened, the sample was cut with a microtome so that the cross-sectional plane formed by the transverse direction and the thickness direction was visible with an optical microscope. An image of the cross section was taken under the light microscope and the wave structure was measured with regard to wave height and wavelength.

2 shows an example of the determination of the wave height and wavelength of the wave structure of the nonwoven. If the nonwoven fabric 20 has a pronounced wave structure on both sides, then the wave height 21 is determined by the distance in the thickness direction 41 between the highest point of the wave crest 24 and the lowest point of the adjacent wave trough 23 on the same side. The wavelength 22 is the distance in the transverse direction 40 between two points of the same phase of the wave structure, shown here as the distance between two adjacent wave crests 24 and 25 by way of example. If the nonwoven fabric 30 has a pronounced wave structure on only one side, then the wave height 31 is determined in the same way by the distance in the thickness direction 41 between the highest point of the wave crest 34 and the lowest point of the adjacent wave trough 33 on the same side. The wavelength 32 is the distance in the transverse direction 40 between two points of the same phase of the wave structure, shown here as the distance between two adjacent wave crests 34 and 35 by way of example. The wave height or the wavelength can be determined as a single value or as an average of several measurements, for example three measurements.

3 Fig. 12 shows the optical microscopic image of the cross-sectional area of the non-woven fabric produced. A wave structure is clearly visible and the wave height 41 was determined to be 220 μm and the wavelength 42 to be 2030 μm.

The non-woven fabric was used as the filter material according to the invention without adding further components, and a segment of a smoking article, wrapped with a wrapping paper with a ^{basis weight of 78 g/m 2} , was produced from it. The segment could be produced without any problems, in particular the pleating could be carried out with considerably reduced pressure. Further experiments showed that pleating could be dispensed with entirely without the production speed having to be reduced or the properties of the segment changing significantly.

For comparison is in 4 a filter material made of 100% cellulose fibers made of paper, i.e. made of a non-hydroentangled material, after it has been pleated by mechanical pressure between two rollers in the manufacture of a segment for a smoking article, but before a segment has been made from it. A cross-sectional sample of this filter material was also analyzed with the light microscope and the wave height and wavelength were measured.

Out 4 a similar wave structure can be seen and here too the wave height 51 was determined to be 390 µm and the wavelength 52 to be 2000 µm. It can be seen that the corrugated structure of the filter material according to the invention is not that of a filter material according to the invention is very similar after pleating, so that the pleating of the filter material according to the invention can take place with significantly less pressure or can be omitted entirely.

These experiments show that the filter material of the present invention can make the pleating step easier or even superfluous compared to filter materials known from the prior art when manufacturing a segment for smoking articles, thus simplifying the manufacturing process and making it less error-prone.

Claims (42)

Filter material for making a segment for a smoking article, wherein the filter material comprises a hydroentangled nonwoven, and the nonwoven comprises fibers, wherein the fibers are selected from the group consisting of wood pulp fibers, fibers of regenerated cellulose and mixtures thereof, and these fibers together in an amount at least 50% and at most 100% of the mass of the hydroentangled nonwoven is contained in the nonwoven, and wherein the nonwoven is web-shaped, has a longitudinal direction in the running direction of the web, a transverse direction orthogonal thereto in the plane of the web and a thickness direction orthogonal to the longitudinal direction and transverse direction and is formed in such a way that the non-woven fabric has a wavy structure with a wave height of at least 50 µm and no more than 1000 µm and a wavelength of at least 150 µm and no more than 5000 µm in the plane spanned by the transverse and thickness directions. filter material claim 1 , in which the wave height is at least 100 µm and at most 900 µm, preferably at least 150 µm and at most 800 µm. filter material claim 1 or 2 , in which the wavelength is at least 300 µm and at most 4000 µm, preferably at least 500 µm and at most 2000 µm. Filter material according to one of the preceding claims, in which the amount of cellulose fibres, regenerated cellulose fibers or said mixture thereof is at least 60% and at most 95%, in each case based on the mass of the hydroentangled nonwoven fabric. Filter material according to one of the preceding claims, in which the cellulose fibers are obtained from coniferous woods, in particular spruce, pine or fir, deciduous trees, hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, cotton or esparto grass, or by a Mixture of two or more pulp fibers of different origins are formed. Filter material according to one of the preceding claims, in which the cellulose fibers are formed at least partially by reinforced pulp or mercerized cellulose. Filter material according to one of the preceding claims, in which the fibers of regenerated cellulose are formed by viscose fibers, modal fibers, Lyocell®, Tencel® or mixtures thereof. Filter material according to one of the preceding claims, in which the hydroentangled nonwoven consists essentially exclusively, but at least to at least 95%, based on the mass of the hydroentangled nonwoven of cellulose fibers, fibers of regenerated cellulose or a mixture thereof. Filter material according to one of Claims 1 until 7 , in which the hydroentangled nonwoven fabric of the filter material contains at least 5% and less than 50%, preferably less than 40% and particularly preferably less than 30% staple fibers of cellulose acetate, based in each case on the mass of the hydroentangled nonwoven fabric. Filter material according to one of the preceding claims, in which the basis weight of the hydroentangled nonwoven fabric is at least 25 g/m ² and at most 150 g/m ² , preferably at least 35 g/m ² and at most 120 g/m ² and particularly preferably at least 40 g/m ² and not more than 100 g/m ² . Filter material according to one of the preceding claims, in which the thickness of the hydroentangled nonwoven fabric is at least 100 µm and at most 1000 µm, preferably at least 120 µm and at most 800 µm and particularly preferably at least 150 µm and at most 750 µm. Filter material according to one of the preceding claims, in which the density of the hydroentangled nonwoven fabric is at least 50 kg/m ³ and at most 300 kg/m ³ , preferably at least 70 kg/m ³ and at most 250 kg/m ³ and particularly preferably at least 80 kg/m ³ and not more than 220 kg/m ³ . Filter material according to one of the preceding claims, in which the width-related tensile strength of the hydroentangled nonwoven fabric is at least 0.05 kN/m and at most 5 kN/m, preferably at least 0.07 kN/m and at most 4 kN/m. Filter material according to one of the preceding claims, in which the elongation at break in the transverse direction of the hydroentangled nonwoven fabric is at least 1% and at most 50%, preferably at least 3% and at most 40%. Filter material according to one of the preceding claims, in which at least 80%, preferably at least 90%, of the mass of the filter material is formed by the hydroentangled nonwoven. Filter material according to one of the preceding claims, which comprises one or more substances selected from the group consisting of triacetin, glycol, propylene glycol, sorbitol, glycerol, polyethylene glycol, polyvinyl alcohol and triethyl citrate or mixtures thereof. A segment comprising a filter material according to any one of the preceding claims and a wrapping material. segment after Claim 17 , wherein the segment is cylindrical with a diameter of 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 Claim 17 or 18 , with 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 claims 17 until 19 whose tensile strength according to ISO 6565:2015 is at least 1 mmWG/mm and at most 12 mmWG/mm and preferably at least 2 mmWG/mm and at most 10 mmWG/mm. segment after one of claims 17 until 20 , whose wrapping material is formed by a paper or a film. segment after one of claims 17 until 21 , whose wrapping material has a weight per unit area 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 after one of claims 17 until 22 , which comprises at least one capsule containing flavorings. Smoking article comprising a segment containing an aerosol generating material and a segment according to any one of claims 17 until 23 . smoking articles after Claim 24 wherein the smoking article is a filter cigarette and the aerosol forming material is tobacco. smoking articles after Claim 24 , when used as intended, the aerosol-forming material is only heated but not burned. Method for producing a filter material for smoking articles, comprising the following steps A to D, A - providing a fibrous web comprising fibers selected from the group consisting of cellulose fibers, regenerated cellulose fibers and mixtures thereof, B - hydroentanglement of the fibrous web by a plurality of water jets directed at the fibrous web, C - creating a wavy structure in the non-woven fabric by means of a large number of water jets directed at the fibrous web, D - drying the hydroentangled nonwoven fabric, wherein the proportion of said fibers in the fibrous web of step A is selected such that these fibers are contained in total in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric in the dried state of step D, wherein the in step A provided fibrous web has a longitudinal direction in the running direction of the fibrous web, a transverse direction orthogonal thereto in the plane of the fibrous web, and a thickness direction orthogonal to the longitudinal direction and transverse direction, and the water jets directed onto the fibrous web are arranged in step C such that they are in the transverse direction from center to center of the water jets having a distance from each other of at least 150 µm and at most 5000 µm when hitting the fibrous web, and the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven fabric obtained in step D in the stretched from the transverse direction and the thickness direction level one Wave structure with a wave height of at least 50 µm and at most 1000 µm, and a wavelength of at least 150 µm and at most 5000 µm. procedure after Claim 27 , in which the water jets for carrying out step B and/or C are directed onto both sides of the fibrous web. procedure after Claim 27 or 28 , in which the water jets in step C are arranged in such a way that they strike points which are intended to form wave troughs when viewed from the respective side. Procedure according to one of claims 27 until 29 , in which the water jets emerge in step from an opening which has an area of at least 450 µm ² and at most 50000 µm ² and is preferably a circular opening. Procedure according to one of claims 27 until 30 , in which the pressure of the water jets in step C is at least 3 MPa and at most 40 MPa, with the pressure for generating the corrugated structure preferably being selected as a function of the running speed of the fibrous web such that the ratio p/v from the pressure p in MPa and the running speed v of the fiber web in m/s: 2.5≦p/v≦20, preferably 3≦p/v≦15. Procedure according to one of claims 27 until 31 , in which the pressure of the water jets in step B is at least 0.5 MPa and at most 60 MPa, preferably at least 1 MPa and at most 50 MPa, the pressure in step B preferably being selected as a function of the running speed of the fibrous web such that for the ratio p/v of the pressure p in MPa and the running speed v of the fiber web in m/s applies: 2≦p/v≦20, preferably 4≦p/v≦8. Procedure according to one of claims 27 until 32 , in which the wave height after step D is at least 100 µm and at most 900 µm, preferably at least 150 µm and at most 800 µm. Procedure according to one of claims 27 until 33 , in which the wavelength after step D is at least 300 μm and at most 4000 μm, preferably at least 500 μm and at most 2000 μm. Procedure according to one of claims 27 until 34 , wherein the hydroentangled nonwoven fabric obtained in step D has any one or any combination of the features that are in claims 1 until 16 is or are defined in connection with the hydroentangled nonwoven fabric as a component of the claimed filter material. Procedure according to one of claims 27 until 35 , in which, in a variant A1 of the method, the fibrous web is provided in step A by a wet-laying method which comprises the following partial steps A1.1 to A1.3: A1.1 - producing an aqueous suspension comprising fibers selected from the group consisting of cellulose fibers, fibers of regenerated cellulose and mixtures thereof, the amount of these fibers being selected such that these fibers are contained in total in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric in the dried state from step D, A1.2 - applying the suspension from step A1.1 to a rotating wire, and A1.3 - dewatering the suspension through the rotating wire to form a fibrous web, the method preferably comprising a further sub-step A1.4: A1. 4 - Adjusting the moisture content of the fibrous web by drying or moistening. procedure after Claim 36 , wherein the aqueous suspension in step A1.1 has a solids content of at least 0.005% and at most 3.0%, preferably at least 0.005% and at most 1.0%, particularly preferably at least 0.01% and at most 0.2% and very particularly preferably at least 0.01% and at most 0.05%. procedure after Claim 36 or 37 , in which the circulating screen of steps A1.2 and A1.3 in the running direction of the fibrous web is at an angle of at least 3° and at most 40° to the horizontal, preferably at an angle of at least 5° and at most 30° and particularly preferably inclined upwards at an angle of not less than 15° and not more than 25°. Procedure according to one of Claims 36 until 38 , in which in step A1.3 the dewatering is supported by creating a pressure difference between the two sides of the revolving wire, the pressure difference preferably being created by vacuum boxes or suitably shaped vanes. Procedure according to one of Claims 36 until 39 , in which drying in step A1.4 is carried out by heated drying cylinders or by hot air and moistening by a spray bar. Procedure according to one of claims 27 until 35 , in which, in a variant A2 of the method according to the invention, the fibrous web is provided in step A by a dry-laying process which comprises the following sub-steps A2.1 and A2.2: A2.1 - producing a fibrous web by a dry-laying process, the fibrous web fibers which are selected from the group consisting of wood pulp fibers, regenerated cellulosic fibers and mixtures thereof, the amount of these fibers being selected such that these fibers are in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric contained in the dried state of step D, and A2.2 - moistening the fibrous web. Procedure according to one of claims 27 until 41 , in which the drying in step D at least partially effected by contact with hot air, by infrared radiation or by microwave radiation, the drying in step D preferably being effected by through-air drying.

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