Pleated filter material for smoking articles

Abstract

A filter material for producing a segment of a smoking article is described, the filter material comprising a hydroentangled nonwoven fabric, the nonwoven fabric comprising fibers selected from the group consisting of pulp fibers, regenerated cellulose fibers, and mixtures thereof, the fibers collectively comprising at least 50% and at most 100% of the weight of the hydroentangled nonwoven fabric, the nonwoven fabric being in the form of a web having a longitudinal direction in the direction of travel of the web, a transverse direction perpendicular to the longitudinal direction and extending within the plane of the web, and a thickness direction perpendicular to the longitudinal and transverse directions. The nonwoven fabric is shaped to have a wave-like structure in the plane formed by the transverse and thickness directions, with a wave height of at least 50 μm and at most 1000 μm, and a wave length of at least 150 μm and at most 5000 μm.

Description

[Technical Field]

[0001] The present invention relates to a filter material suitable for the manufacture of smoking article segments, the filter material being pleated, from which smoking article segments can be manufactured in an efficient manner, and also to smoking article segments manufactured from the filter material. [Background technology]

[0002] Smoking articles are typically rod-shaped articles consisting of at least two rod-shaped segments arranged adjacent to one another, one segment comprising a material capable of forming an aerosol when heated, and at least one further segment serving to influence the properties of the aerosol.

[0003] The smoking article may be a filtered cigarette, in which a first segment comprises an aerosol-forming material, in particular tobacco, and a further segment is designed as a filter and serves 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 defined draw resistance for the filtered cigarette.

[0004] However, the smoking article may also be known as a heated tobacco product, in which the aerosol-forming material is only heated and not burned. This means that the number and amount of substances in the aerosol that are harmful to health are reduced. Such smoking articles also consist of at least two, often more, and particularly four segments. One segment typically contains the aerosol-forming material, which includes tobacco, reconstituted tobacco, or tobacco prepared by other processes. Furthermore, optional segments of the smoking article may serve to transport the aerosol, cool the aerosol, or filter the aerosol.

[0005] The segments are usually wrapped in a packaging material, very often paper.

[0006] Unless expressly stated below or directly apparent from the context, "segment" should be understood to refer to a segment of a smoking article that does not include aerosol-forming material, but rather serves, for example, to transport, cool, or filter the aerosol.

[0007] In the prior art, it is known to form such segments from polymers such as cellulose acetate or polylactide. After consumption of a smoking article, it must be disposed of in an appropriate manner. However, in many cases, consumers simply discard the consumed smoking article into the environment, and attempts to restrict this behavior through summary prosecution or fines have met with little success.

[0008] Because cellulose acetate and polylactide biodegrade very slowly in the environment, paper and cellulosic nonwovens are becoming increasingly important. During segment production, a web of paper or cellulosic nonwoven is first pleated longitudinally, then formed into a continuous rod and wrapped in packaging material. The continuous rod is then cut into pieces suitable for further processing.

[0009] During pleating, the web passes over two rollers bearing a pattern that is embossed into the web under high pressure. Typically, the pattern is a line pattern oriented in the direction of web travel. The embossed lines weaken the web in the transverse direction, perpendicular to the direction of travel, so that the web can be more easily gathered laterally to form a continuous rod.

[0010] However, during pleating, due to the high pressure of the rollers, it can happen that the web is cut longitudinally, which can cause tears during further processing or other technical problems. Therefore, there is a need for a filter material that does not have this drawback, or to a lesser extent, but which is otherwise as identical as possible to other known filter materials.

[0011] German Patent Application Publication No. 102005017478 describes a tobacco smoke filter containing fibers derived from regenerated cellulose (e.g., lyocell) and containing an adsorbent. Two or more adsorbents are added to the fibers of the tobacco smoke filter, and / or the tobacco smoke filter contains an adsorbent between the fibers. This document describes that such a tobacco smoke filter can achieve a high adsorbent loading. In one embodiment, nonwoven fabrics were manufactured from loaded lyocell staple fibers. One nonwoven fabric was loaded with 50% by weight of "Siralox 40" (Sasol Ltd.) in the lyocell fibers used for its manufacture. The other nonwoven fabric was loaded with 50% by weight of HY-zeolite in the fibers. Activated carbon granules were added to one of the two nonwoven fabric layers, and then the two layers were connected to each other by needling. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] German Patent Application Publication No. 102005017478 Summary of the Invention

[0013] The object of the present invention is to provide a filter material for smoking articles which can be processed into segments of smoking articles with high productivity and which is otherwise as similar as possible to conventional filter materials in terms of its properties.

[0014] 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, as well as by a process for producing a filter material according to the invention according to claim 27. Advantageous embodiments are provided in the dependent claims.

[0015] The inventors have found that this object can be achieved by a filter material for producing segments of a smoking article, the filter material comprising a hydroentangled nonwoven fabric, the nonwoven fabric comprising fibers selected from the group consisting of pulp fibers, regenerated cellulose fibers, and mixtures thereof, which fibers are collectively contained in the nonwoven fabric in an amount of at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric, the nonwoven fabric being in the form of a web and having a longitudinal direction in the running direction of the web, a transverse direction extending within the plane of the web and perpendicular to the longitudinal direction, and a thickness direction perpendicular to the longitudinal and transverse directions, the nonwoven fabric being shaped so as to have a wave height in the plane formed by the transverse and thickness directions of at least 50 μm and at most 1000 μm, and a wave length of at least 150 μm and at most 5000 μm.

[0016] While the term "hydroentanglement" primarily denotes the underlying manufacturing process, hydroentangled nonwovens must be considered to have distinctive structural properties that distinguish them from other nonwovens and that, to the inventors' knowledge, cannot be obtained in the same way by other manufacturing processes. For example, except in the case of paper, where strength is primarily due to hydrogen bonding and the fibers are primarily oriented in the plane of the paper, the strength of hydroentangled nonwovens is obtained by entanglement of the fibers, and therefore a significant proportion of the fibers are also oriented through the thickness of the nonwoven.

[0017] During the production of the hydroentangled nonwoven fabric according to the invention, the fibers are deposited on a water-permeable wire and consolidated by a number of water jets arranged transversely and directed onto the fibers. By specially selecting the arrangement and characteristics of the water jets, according to the invention, it is possible to produce a wave-like structure in the transverse direction, similar to that obtainable by pleating. Therefore, the nonwoven fabric and the filter material according to the invention comprising the nonwoven fabric are prepleated.

[0018] During the production of continuous rods from the filter material according to the invention, the filter material passes through two rollers provided with a pattern. Because the filter material according to the invention is already prepleated, substantially less pressure is required to obtain sufficient pleating of the filter material, or even pleating can be omitted altogether. This significantly reduces the possibility of accidentally cutting the filter material longitudinally. In this way, the number of interruptions during the production of continuous rods and segments can be reduced, increasing productivity, which represents a substantial advantage of the filter material according to the invention.

[0019] The nonwoven fabric is in the form of a web and has a longitudinal direction in the direction of web travel and a direction perpendicular to the longitudinal direction and extending within the web plane, referred to as the transverse direction. The direction perpendicular to the longitudinal and transverse directions is referred to as the thickness direction. The nonwoven fabric contained in the filter material of the present invention has a cross-sectional area that is a wave-like structure in a plane formed by the transverse and thickness directions, where the wavelength extends substantially in the transverse direction and the wave height extends substantially in the thickness direction. According to the present invention, the wave height is at least 50 μm and at most 1000 μm, preferably at least 100 μm and at most 900 μm, particularly preferably at least 150 μm and at most 800 μm. According to the present invention, the wavelength is at least 150 μm and at most 5000 μm, preferably at least 300 μm and at most 4000 μm, particularly preferably at least 500 μm and at most 2000 μm.

[0020] The shape of the wavy structure is not particularly important, but it must be strong and prominent enough to make the nonwoven fabric easier to collect laterally than the same nonwoven fabric without the wavy structure. Due to the manufacturing process, the wave height and wavelength may also vary substantially within the cross-sectional area. This is not important for the effectiveness of the present invention, as long as the wavelength and wave height are within the indicated ranges over most of the cross-sectional area, particularly over at least 60%, preferably at least 75% of the cross-sectional area.

[0021] The wavy structure also does not need to be prominent on the upper and lower sides of the nonwoven; it is sufficient if it is prominent on one side, as the thin areas created by this in the wave troughs facilitate lateral gathering of the nonwoven and therefore reduce the pressure required for pleating during the production of the segments.

[0022] Surface roughness alone is generally not sufficient to achieve the effects of the present invention.

[0023] The wavy structure of a nonwoven fabric can be determined by embedding a sample of the nonwoven fabric in a suitable epoxy resin. After the epoxy resin is cured, the sample can be milled or cut with a microtome at the cross-sectional plane of the nonwoven fabric, so that the cross-sectional area is visible under an optical microscope. The optical microscope allows the wavy structure to be visualized and the wave height and wavelength to be measured. A camera connected to the optical microscope can serve to record an image of a section of the cross-sectional area.

[0024] The conditions set forth for wave height and wavelength are fully met for the present invention when met on a representative section of the cross-sectional area. Because the manufacturing process generally results in the wave structure varying only slightly across the length of the nonwoven, it is not necessary to perform such measurements on several cross-sectional areas in the length direction to test the wave height and wavelength requirements.

[0025] As an alternative to an optical microscope, a scanning electron microscope can also be used.

[0026] For good tensile strength of the segments made from the filter material according to the invention and for adjusting the draw resistance or filtration efficiency, the hydroentangled nonwoven contains pulp fibers, fibers derived from regenerated cellulose, or a mixture thereof in an amount of at least 50% and at most 100% by weight of the hydroentangled nonwoven. Preferably, the amount of fibers is at least 60% and at most 95% by weight of the hydroentangled nonwoven, respectively.

[0027] The pulp fibers can be preferably sourced from coniferous or deciduous woods, or from other plants such as hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, cotton, or Esperanto grass. Mixtures of pulp fibers of different origins can also be used. Particularly preferably, the pulp fibers are sourced from coniferous woods, such as spruce, pine, or fir, because these fibers, due to their length, provide good strength in hydroentangled nonwoven fabrics. Pulps sourced from coniferous woods, known as reinforced pulps, which provide particularly high strength, and mercerized pulps, which provide particularly high thickness and low density, are more particularly preferred.

[0028] The pulp fibers can be bleached or unbleached. Bleached pulp fibers offer advantages for the appearance of segments made from the filter material according to the invention due to their white color, while unbleached pulp fibers, which have a resulting light to dark brown color, are more environmentally friendly since the bleaching process can be omitted. A mixture of bleached and unbleached pulp fibers can also be used to better adjust the color of the filter material according to the invention.

[0029] The regenerated cellulose-derived fibers are preferably viscose fibers, modal fibers, Lyocell®, Tencel®, or mixtures thereof, which have good biodegradability and can be used to optimize the strength, thickness, or density of the hydroentangled nonwoven fabric and to adapt the filtration efficiency of the segments produced therefrom to the smoking article.

[0030] In a more particularly preferred embodiment, the filter material according to the invention comprises a hydroentangled nonwoven fabric, which consists essentially exclusively, but at least 95% by weight of the hydroentangled nonwoven fabric, of pulp fibers, fibers derived from regenerated cellulose, or mixtures thereof. This more particularly preferred embodiment allows for very good biodegradability and rapid degradation upon contact with water, while at the same time allowing for a very low impact on the taste of smoking articles made from the filter material.

[0031] In a preferred embodiment of the filter material according to the invention, the hydroentangled nonwoven comprises at least 5% and less than 50%, particularly preferably less than 40%, more particularly preferably less than 30% staple fibers of cellulose acetate, the percentages being based on the mass of the hydroentangled nonwoven.

[0032] Additives such as alkenyl ketene dimers (AKD), alkenyl succinic anhydrides (ASA), fatty acids, starches, starch derivatives, carboxymethyl cellulose, alginates, or substances for adjusting pH, such as organic or inorganic acids or their salts or bases, can be added to adjust specific properties of the nonwoven fabric. Those skilled in the art can determine the type and amount of such additives empirically.

[0033] The basis weight of the hydroentangled nonwoven fabric is preferably at least 25 g / m 2 and a maximum of 150 g / m 2 , particularly preferably at least 35 g / m 2 and a maximum of 120 g / m 2 , more particularly preferably at least 40 g / m 2 and a maximum of 100 g / m 2 Basis weight affects the tensile strength of the hydroentangled nonwoven fabric, with higher basis weights resulting in higher tensile strength.

[0034] The thickness of the hydroentangled nonwoven fabric is preferably at least 100 μm and at most 1000 μm, particularly preferably at least 120 μm and at most 800 μm, and more particularly preferably at least 150 μm and at most 750 μm. The thickness affects the amount of filter material that can be packed into a smoking article segment, and thus the segment's resistance to draw and filtration efficiency. It also affects the processability of the filter material, since a high thickness can make pleating the filter material more difficult. The filter material of the present invention allows for a high thickness due to the nonwoven's corrugated structure without causing problems during pleating. Therefore, the filter material of the present invention is particularly well suited for use when producing high-density, high-resistance filter segments. The measurement of thickness is affected by the corrugated structure of the material. However, for purposes of determining thickness, this fact is ignored, as the thickness measured in this way can also serve as a measure of how much filter material can be wound onto a reel of a given diameter. Thickness can be measured in accordance with EDANA Standard Procedure NWSP 120.6.R0(15).

[0035] The density of the hydroentangled nonwoven fabric can be determined by dividing the basis weight by the thickness. The density of the hydroentangled nonwoven fabric is preferably at least 50 kg / m 3 and a maximum of 300 kg / m 3 , particularly preferably at least 70 kg / m 3 and a maximum of 250 kg / m 2 , more particularly preferably at least 80 kg / m 3 and maximum 220 kg / m 3 These values ​​relate to the density before a segment of a smoking article is manufactured from the filter material according to the present invention comprising the hydroentangled nonwoven. The density of the hydroentangled nonwoven determines, inter alia, the resistance to draw and filtration efficiency of the segment of a smoking article manufactured therefrom. The preferred range allows for a good combination of resistance to draw and filtration efficiency.

[0036] The mechanical properties of the hydroentangled nonwoven are important for the processability of the filter material according to the invention into segments of smoking articles. The tensile strength across the width 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.

[0037] The breaking elongation of the hydroentangled nonwoven fabric is important when the filter material according to the present invention is processed to produce segments of smoking articles, since the filter material is pleated, where a particularly high breaking elongation is advantageous. In this regard, the wavy structure of the nonwoven fabric allows a particularly high breaking elongation in the cross direction, facilitating pleating during the production of the segments. The breaking elongation of the hydroentangled nonwoven fabric in the cross direction is preferably at least 1% and at most 50%, particularly preferably at least 3% and at most 40%.

[0038] The tensile strength and elongation at break may depend on the direction in which the sample for measurement is taken from the hydroentangled nonwoven. The requirements for tensile strength of a hydroentangled nonwoven are met if the tensile strength in at least one direction is within the indicated, preferred, or particularly preferred range. The elongation at break is shown and is measured in the cross direction.

[0039] The filter material according to the invention comprises a hydroentangled nonwoven fabric, however, preferably the hydroentangled nonwoven fabric according to the invention constitutes the overwhelming majority of the filter material, so that preferably at least 80% of the mass of the filter material is formed by the hydroentangled nonwoven fabric, and particularly preferably at least 90% of the mass of the filter material is formed by the hydroentangled nonwoven fabric.

[0040] Apart from the hydroentangled nonwoven, the filter material according to the invention can comprise further components that affect, for example, the processability of the filter material or the properties of segments made from the filter material or the taste of the smoking article, including, for example, flavorants, flavorant carriers, in particular impregnation of the nonwoven with flavorant-impregnated filaments, or substances that increase the stiffness of the filter material or the hardness of filters made from the filter material.

[0041] In a preferred embodiment of the filter material according to the present invention, the filter material comprises a hydroentangled nonwoven fabric 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, which may aid in improving the filtration efficiency to match that of cellulose acetate.

[0042] If at least 90% of the mass of the filter material is formed by hydroentangled nonwoven fabric, the achievement of the above-mentioned characteristics of the hydroentangled nonwoven fabric, for example with respect to the pulp fiber content, the content of fibers derived from regenerated cellulose, the density, thickness, basis weight, tensile strength, and elongation at break, can also be tested on the filter material itself, without the need to separate the hydroentangled nonwoven fabric from the filter material. Therefore, the above-mentioned ranges, and preferred, particularly preferred, and more particularly preferred ranges and properties according to the present invention are also valid for filter materials made from hydroentangled nonwoven fabric.

[0043] Segments for smoking articles according to the present invention can be manufactured from filter materials according to the present invention using processes known in the art. These processes include, for example, pleating the filter material, forming a continuous rod from the pleated filter material, wrapping the continuous rod in a wrapping material, and cutting the wrapped rod into individual rods of defined length. Often, the length of such rods will be an integer multiple of the length of the segments to be used in smoking articles according to the present invention, and therefore the rods are cut into segments of the desired length before or during the manufacture of the smoking articles.

[0044] A segment for a smoking article according to the present invention comprises a filter material according to the present invention and a wrapping material.

[0045] In a preferred embodiment of the segments according to the invention, the segments are 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 particularly advantageous for the use of the segments according to the invention in smoking articles.

[0046] 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, more particularly preferably at least 10 mm and at most 28 mm.

[0047] The resistance to draw of a segment determines, among other things, the pressure differential that a smoker must apply during consumption of the smoking article to generate a certain volumetric flow rate through the smoking article, and thus substantially influences the smoker's acceptance of the smoking article. The resistance to draw of a segment can be measured according to ISO 6565:2015 and is given in mm water gauge (mmWG). To a very good approximation, the resistance to draw of a segment is proportional to the length of the segment, so measurements of the resistance to draw can also be performed on rods that differ from the segment only in terms of their length. This allows the resistance to draw of the segment to be easily calculated.

[0048] The resistance to attraction of the segment per unit length of the segment is preferably at least 1 mmWG / mm and at most 12 mmWG / mm, particularly preferably at least 2 mmWG / mm and at most 10 mmWG / mm.

[0049] The packaging material for the segments according to the invention is preferably paper or foil.

[0050] The packaging material for the segments according to the invention preferably has a mass of at least 20 g / m 2 and a maximum of 150 g / m 2 , particularly preferably at least 30 g / m 2 and a maximum of 130 g / m 2 Packaging materials with this preferred or particularly preferred basis weight provide a particularly advantageous hardness to the segments according to the invention wrapped therein, thereby avoiding the possibility that the smoker may accidentally crush the segments of the smoking article.

[0051] In a preferred embodiment, the segment according to the invention further comprises at least one capsule containing a flavoring agent, the capsule often being designed so that the smoker can break it with finger pressure, thereby releasing the flavoring agent and thereby altering the taste of the smoking article.

[0052] Smoking articles according to the present invention can be manufactured from segments according to the present invention according to processes known in the art.

[0053] A smoking article according to the present invention comprises a segment including an aerosol-forming material, a segment comprising a filter material according to the present invention, and a wrapping material.

[0054] In a preferred embodiment, the smoking article is a filtered cigarette and the aerosol-forming material is tobacco.

[0055] In a preferred embodiment, the smoking article is one in which the aerosol-forming material is only heated, not combusted, during intended use.

[0056] The hydroentangled nonwoven fabric for a filter material according to the present invention can be produced according to the following process according to the present invention, which includes the following steps A to D. A - providing a fiber web comprising fibers selected from the group consisting of pulp fibers, fibers derived from regenerated cellulose, and mixtures thereof; B - Hydroentangling the fibrous web by a plurality of water jets directed onto the fibrous web; generating a wave-like structure in the nonwoven fabric by a plurality of water jets directed onto the C-fiber web; and D- Drying the hydroentangled nonwoven fabric; The proportion of the fibers in the fibrous web in step A is selected so that these fibers collectively account for at least 50% and at most 100% of the mass of the dry hydroentangled nonwoven fabric from step D; the fibrous web provided in step A has a longitudinal direction in the running direction of the fibrous web, a transverse direction perpendicular to the longitudinal direction and extending within the plane of the fibrous web, and a thickness direction perpendicular to the longitudinal and transverse directions; the water jets directed onto the fibrous web in step C are arranged so that the water jets are spaced apart from each other at a lateral distance from the center point of the water jet to the center point of the water jet at the point of impingement on the fibrous web of at least 150 μm and at most 5000 μm; 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 has a wavy structure in the plane formed by the transverse and thickness directions 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 this specification and the remainder of this disclosure, the "waterjet pressure" is, as is customary, the pressure within the pressure chamber used to generate the waterjet.

[0057] According to the inventors' findings, a water jet with a sufficiently high pressure is suitable for creating depressions in the nonwoven fabric passing under the water jet, which can be recognized as wave troughs in the cross-sectional area. A pressure of at least 2 MPa is required for this purpose, but this pressure depends substantially on the speed at which the fibrous web passes through the machine. Higher speeds require higher pressures. At correspondingly high pressures, the fibers are not only entangled but also partially displaced, which substantially contributes to the formation of a wavy structure. During water jet processing, the fibrous web is typically supported by a wire, and since the fibers are primarily displaced where the wire is permeable, the wire structure should preferably be selected to suit the intended wavy structure.

[0058] In the prior art, during hydroentangling of nonwoven fabrics, the water jets are not positioned at defined positions relative to the fibrous web, but rather are positioned so that uniform entanglement can be achieved by the water jets over the entire area of ​​the running fibrous web, however this does not result in the wavy structure characteristic of the filter material according to the invention, even when the water jet pressure exceeds 2 MPa.

[0059] Therefore, according to the present invention, the water jets serving to generate the wavy structure must be positioned accordingly, in particular so that the high-pressure water jets are not directed onto the areas of the fiber web where wave crests are to be created. Therefore, the water jets serving to generate the wavy structure in step C are laterally offset and spaced apart from one another by a distance from the center of the water jets at the point of their impingement on the fiber web of at least 150 μm and at most 5000 μm. The water jets can be positioned arbitrarily in the longitudinal direction.

[0060] It is also possible to direct water jets onto both sides of the fibrous web to carry out step B or C. Preferably, the water jets in step C are positioned so that they hit those areas from each side where wave troughs should be formed.

[0061] The pressure of the water jets which serve to entangle the nonwoven in step B can also exceed 2 MPa and can be chosen to be substantially higher, especially for faster fibrous web speeds. According to the invention, the only important factor is that the effect of all the water jets over the area of ​​the fibrous web is not so uniformly distributed that it is not possible to generate a wavy structure.

[0062] According to the present invention, the water jet for generating the wavy structure in step C requires a pressure of at least 2 MPa and at most 70 MPa. According to the inventors' findings, a pressure below 2 MPa does not generate a significant wavy structure, and a pressure above 70 MPa risks cutting the fibrous web even at higher speeds. Preferably, the water jet pressure in step C is at least 3 MPa and at most 40 MPa. The pressure for generating the wavy structure may depend on the speed of the fibrous web, whereby the ratio p / v of the pressure p (MPa) to the speed v (m / s) of the fibrous web is preferably selected so that 2.5≦p / v≦20, preferably 3≦p / v≦15.

[0063] Preferably, the water jet in step C has a diameter of at least 450 μm 2 and a maximum of 50,000 μm 2 and exits through an opening which is preferably a circular opening.

[0064] The pressure of the water jet in step B is preferably at least 0.5 MPa and at most 60 MPa, particularly preferably at least 1 MPa and at most 50 MPa, and the high pressure should be mainly combined with the high speed of the fiber web to avoid cutting the fiber web. The pressure for entangling the fiber web can depend on the speed of the fiber web, whereby the ratio p / v of the pressure p (MPa) to the speed v (m / s) is preferably selected so that 2≦p / v≦10, preferably 4≦p / v≦8.

[0065] The wavy structure is characterized by a wave height and wavelength that can be detected in the cross-sectional area of ​​the nonwoven fabric. According to the present 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, particularly preferably at least 150 μm and at most 800 μm. According to the present 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, particularly preferably at least 500 μm and at most 2000 μm.

[0066] The hydroentangled nonwoven fabric produced according to this process should be suitable for use in the above-mentioned filter material, which means in particular that the hydroentangled nonwoven fabric can have all the features described above, individually or in combination, in relation to the hydroentangled nonwoven fabric as a component of the filter material and as defined in the claims directed to the filter material.

[0067] The fibrous web of step A can be provided using a variety of processes, for example, by a wet-laid process or an air-laid process.

[0068] In a preferred variant A1 of the process according to the invention, the fibrous web in step A is provided by a wet-laid process comprising the substeps A1.1 to A1.3: A1.1 - preparing an aqueous suspension comprising fibers selected from the group consisting of pulp fibers, regenerated cellulose fibers, and mixtures thereof, the amount of fibers being selected so that these fibers together comprise at least 50% and at most 100% of the mass of the dry hydroentangled nonwoven fabric from step D; A1.2 - applying the suspension from step A1.1 to the running wire; and A1.3 - a substep of dewatering the suspension by means of a traveling wire to form a fiber web, The process preferably comprises a further sub-step A1.4: A1.4—Substep of adjusting the moisture content of the fibrous web by drying or wetting.

[0069] In a preferred embodiment of variant A1 of the process 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%, preferably at least 0.005% and at most 1.0%, particularly preferably at least 0.01% and at most 0.2%, more particularly preferably at least 0.01% and at most 0.05%. A suspension with a particularly low solids content makes it possible to form an even lower density fibrous web in step A1.3.

[0070] In a preferred embodiment of process variant A1 according to the invention, the running wires of steps A1.2 and A1.3 are inclined upwards in the longitudinal direction of the fibrous web relative to the horizontal by an angle of at least 3° and at most 40°, preferably at least 5° and at most 30°, particularly preferably at least 15° and at most 25°.

[0071] In a preferred embodiment of variant A1 of the process according to the invention, the dewatering in step A1.3 is assisted by creating a pressure difference between the two sides of the running wire, which pressure difference is preferably created by a vacuum box or by a suitably shaped vane.

[0072] In a preferred embodiment of process variant A1 according to the invention, drying in step A1.4 is carried out by means of heated drying cylinders or hot air, and wetting is carried out by means of spray bars. The drying process or wetting serves to optimally adjust the moisture content of the fibrous web for hydroentanglement in step B. In particular, in step A1.4, the fibrous web can first be dried to approximately the equilibrium moisture content at normal room temperature and relative humidity, and then the fibrous web is rolled up and conveyed to a separate device that carries out hydroentanglement, where it is unrolled and the moisture content is adjusted by means of spray bars for the next step B.

[0073] In a preferred variant A2 of the process according to the invention, the fibrous web in step A is provided by an airlaid process comprising steps A2.1 and A2.2: A2.1 - Producing a fibrous web by an airlaid process, the fibrous web comprising fibers selected from the group consisting of pulp fibers, regenerated cellulose fibers, and mixtures thereof, the amount of these fibers being selected so that they together comprise at least 50% and at most 100% by weight of the dry hydroentangled nonwoven fabric from step D; and A2.2 - Wetting the fibrous web.

[0074] Such an airlaid process of Variant A2 may be advantageous because it may eliminate the energy-intensive drying in step A1.4 of Variant A1, for example.

[0075] In a preferred embodiment of the process according to the invention, drying in step D is carried out at least partially by contact with hot air, infrared radiation or microwave radiation. In a more particularly preferred embodiment of the process according to the invention, drying in step D is carried out by through-air drying. By through-air drying, also known in the technical field as TAD, the fibrous material is dried by forcing a warm gas flow, in particular an air flow, through the fibrous material. This through-air drying allows obtaining hydroentangled nonwovens of the best quality. Drying by direct contact with a heated surface is also possible, but is less preferred, as this can destroy the wave structure of the hydroentangled nonwoven. [Brief explanation of the drawings]

[0076] [Figure 1] 1 shows an apparatus capable of carrying out the process according to the invention for producing hydroentangled nonwoven fabrics. [Figure 2] An example is the determination of the wave height and wavelength of a wavy structure in a nonwoven fabric. [Figure 3] 1 shows a cross-sectional area of ​​a nonwoven fabric for a filter material according to the present invention. [Figure 4] 3 shows a cross-sectional area of ​​a filter material not according to the invention after pleating. DETAILED DESCRIPTION OF THE INVENTION

[0077] Several preferred embodiments of the filter material and the process for producing the hydroentangled nonwoven are described below.

[0078] To produce the hydroentangled nonwoven fabric contained in the filter material according to the present invention, the process described below was used, using the apparatus shown schematically in FIG.

[0079] An aqueous suspension 1 of pulp and regenerated cellulose fibers was pumped from a storage tank 2 onto a traveling wire 3, inclined upward relative to the horizontal, and dewatered by a vacuum box 9, forming a fibrous web 4 on the wire; its general direction of movement is indicated by arrow 10. The fibrous web 4 was removed from the wire 3 and transferred to a supporting wire 5, which was also traveling. If necessary, this transfer could be facilitated by a pickup roll or by entangling the fibrous web with water jets before transfer. On the supporting wire 5, water jets 11 from a device 6 arranged in three rows transversely to the fibrous web 4 were directed onto the fibrous web 4 to entangle the fibers and consolidate the fibrous web 4 to form a nonwoven fabric. In a further step, higher-pressure water jets 12 were also directed onto the fibrous web 4 by an additional device 7 to generate the aforementioned wave-like structure. In contrast to device 6, device 7 was configured so that the water jets 12 of both longitudinally consecutive rows were directed as close as possible to the same position in the transverse direction. Thus, viewed longitudinally, the second row of water jets 12 was directed into the troughs of the waves created by the first row of water jets 12, thus reinforcing the wavy structure created by the first row. Optional device 6a may direct additional water jets 11a onto the fibrous web, which, depending on their placement and pressure, may serve not only to entangle the nonwoven but also to create or reinforce the wavy structure. In contrast to the representation in Figure 1, the water jets of device 6a may be directed onto the fibrous web 4 from the same side as water jets 11 or 12. The still-wet nonwoven then passed through a through-air dryer 8, where it was dried.

[0080] To produce the hydroentangled nonwoven fabric, a mixture of 80% by weight pulp fibers and 20% by weight Lyocell® fibers was used. Fiber entanglement was performed by three rows of water jets 11, generated at pressures of 3 MPa, 5 MPa, and 6 MPa in the machine direction. The wavy structure of the nonwoven fabric was created by two rows of water jets 12, which were generated at a pressure of 8.5 MPa in both rows. The devices 7 for generating both rows of water jets 12 were laterally spaced 2000 μm apart and had a diameter of 100 μm. The speed of the fiber web was a relatively low 50 m / min. At higher speeds, the pressure of the water jets 11 and 12 had to be increased accordingly. The ratio p / v of the water jet pressure p (MPa) for entangling the fiber web to the fiber web speed v (m / s) was obtained as 3 / (50 / 60) = 3.6 to 6 / (50 / 60) = 7.2. The ratio p / v of the water jet pressure p to the fiber web velocity (m / s) to generate the wavy structure was 8.5 / (50 / 60)) = 10.2.

[0081] The nonwoven fabric produced by this method has a basis weight of 49.6 g / m 2 The thickness according to NWSP 120.6.R0(15) is 522 μm and the density is 95 kg / m 3 The tensile strength in the longitudinal direction was 8.6 N / 15 mm, and the elongation at break in the transverse direction was 31%.

[0082] The nonwoven samples were embedded in epoxy resin, and after the epoxy resin was cured, the samples were cut with a microtome, so that the cross sections formed in the transverse and thickness directions were visible under an optical microscope, where images of the cross sections were recorded and the wavy structure was measured in terms of wave height and wavelength.

[0083] FIG. 2 illustrates, by way of example, the determination of the wave height and wavelength of a wavy structure in a nonwoven fabric. When a nonwoven fabric 20 has pronounced wavy structures on both sides, the wave height 21 is determined by the distance in the thickness direction 41 between the highest point of a wave crest 23 and the lowest point of an adjacent wave trough 23 on the same side. The wavelength 22 is the distance in the lateral direction 40 between two points of equal phase angle in the wavy structure, shown here as the distance between two adjacent wave crests 24 and 25 by way of example. When a nonwoven fabric 30 has pronounced wavy structures on only one side, the wave height 31 is determined in the same way as the distance in the thickness direction 41 between the highest point of a wave crest 34 and the lowest point of an adjacent wave trough 33 on the same side. The wavelength 32 is the distance in the lateral direction 40 between two points of equal phase angle in the wavy structure, shown here as the distance between two adjacent wave crests 34 and 35 by way of example. The wave height or wavelength can be determined as a single value or as the average of several measurements, for example, three measurements.

[0084] Figure 3 shows an image taken of a cross-sectional area of ​​the produced nonwoven fabric under an optical microscope. The wavy structure was clearly discernible, with a wave height 41 determined to be 220 μm and a wavelength 42 of 2030 μm.

[0085] The nonwoven fabric was used as a filter material according to the invention without the addition of further components, from which 78 g / m 2 Segments of smoking articles were produced that were wrapped in a wrapper having a basis weight of 1000g. The production of the segments was possible without any problems, and in particular, pleating could be carried out at a substantially reduced pressure. Further experiments showed that pleating could also be omitted entirely without the need to reduce the production speed or substantially changing the properties of the segments.

[0086] For comparison, Figure 4 shows a filter material not according to the invention, consisting of paper made from 100% pulp fibers, i.e., not a hydroentangled material, after it has been pleated by mechanical pressure between two rolls during the production of segments for smoking articles, but before segments have been produced therefrom. Cross-sectional samples were also analyzed under an optical microscope, and wave height and wavelength were measured using this filter material.

[0087] A similar wave structure can be seen in Figure 4, where again the wave height 51 was determined to be 390 µm and the wavelength 52 was 2000 µm. It can be seen that the wave structure of the filter material according to the invention is similar to the wave structure of the filter material not according to the invention after pleating, and therefore that pleating of the filter material according to the invention can be carried out with substantially less pressure or can be omitted altogether.

[0088] These experiments show that the filter material according to the invention can facilitate or completely avoid the pleating step during the manufacture of segments for smoking articles compared to filter materials known from the prior art, thus simplifying the manufacturing process and reducing its susceptibility to errors.

Claims

1. A filter material for manufacturing a segment of a smoking article, the filter material comprising a hydroentangled nonwoven fabric (20, 30, 40), the nonwoven fabric (20, 30, 40) comprising fibers, the fibers being selected from the group consisting of pulp fibers, regenerated cellulose fibers, and mixtures thereof, the fibers being collectively contained in the nonwoven fabric (20, 30, 40) in an amount of at least 50% and at most 100% by mass of the hydroentangled nonwoven fabric (20, 30, 40), the nonwoven fabric (20, 30, 40) comprising a web a longitudinal direction in the running direction of the web, a transverse direction perpendicular to the longitudinal direction and extending within the plane of the web, and a thickness direction perpendicular to the longitudinal direction and the transverse direction, and the nonwoven fabric (20, 30, 40) is shaped to have a wave-like structure in the plane formed by the transverse direction and the thickness direction, the wave height (21, 31, 41) being at least 50 μm and at most 1000 μm, and a wavelength (22, 32, 42) being at least 150 μm and at most 5000 μm.

2. 2. The filter material according to claim 1, wherein the wave height (21, 31, 41) is at least 100 μm and at most 900 μm, preferably at least 150 μm and at most 800 μm.

3. 3. The filter material according to claim 1 or 2, wherein the wavelengths (22, 32, 42) are at least 300 μm and at most 4000 μm, preferably at least 500 μm and at most 2000 μm.

4. 4. The filter material according to claim 1, wherein the amount of pulp fibers, regenerated cellulose fibers, or the mixture thereof is at least 60% and at most 95% of the mass of the hydroentangled nonwoven fabric (20, 30, 40), respectively.

5. 5. The filter material according to claim 1, wherein the pulp fibres are sourced from softwood, in particular spruce, pine or fir, deciduous wood, hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, cotton or escarpment, or are formed by a mixture of two or more different pulp fibres from these sources.

6. 6. The filter material according to any one of claims 1 to 5, wherein the pulp fibers are at least partially formed by reinforced pulp or mercerized pulp.

7. 7. The filter material according to any one of claims 1 to 6, wherein the fibers of regenerated cellulose are formed by viscose fibers, modal fibers, Lyocell®, Tencel®, or mixtures thereof.

8. 8. The filter material of any one of claims 1 to 7, wherein the hydroentangled nonwoven fabric (20, 30, 40) consists substantially exclusively, but at least 95% by weight of the hydroentangled nonwoven fabric (20, 30, 40) of pulp fibers, regenerated cellulose fibers, or a mixture thereof.

9. 8. The filter material according to claim 1, wherein the hydroentangled nonwoven fabrics (20, 30, 40) of the filter material each comprise at least 5% and less than 50%, preferably less than 40%, particularly preferably less than 30% of staple fibers derived from cellulose acetate, based on the mass of the hydroentangled nonwoven fabric (20, 30, 30).

10. The basis weight of the hydroentangled nonwoven fabric (20, 30, 40) is at least 25 g / m ２ and a maximum of 150 g / m ２ , preferably at least 35 g / m ２ and a maximum of 120 g / m ２ , particularly preferably at least 40 g / m ２ and a maximum of 100 g / m ２ 10. The filter material of claim 1, wherein

11. 11. The filter material according to claim 1, wherein the thickness of the hydroentangled nonwoven fabric (20, 30, 40) is at least 100 μm and at most 1000 μm, preferably at least 120 μm and at most 800 μm, particularly preferably at least 150 μm and at most 750 μm.

12. The density of the hydroentangled nonwoven fabric (20, 30, 40) is at least 50 kg / m ３ and a maximum of 300 kg / m ３ , preferably at least 70 kg / m ３ and maximum 250 kg / m ３ , particularly preferably at least 80 kg / m ３ and maximum 220 kg / m ３ 12. The filter material of claim 1, wherein:

13. 13. The filter material according to any one of claims 1 to 12, wherein the hydroentangled nonwoven (20, 30, 40) has a tensile strength over width of 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.

14. 14. The filter material according to any one of claims 1 to 13, wherein the hydroentangled nonwoven (20, 30, 40) has a crosswise elongation at break of at least 1% and at most 50%, preferably at least 3% and at most 40%.

15. 15. The filter material according to any one of claims 1 to 14, wherein at least 80%, preferably at least 90% of the mass of the filter material is formed by the hydroentangled nonwoven fabric (20, 30, 40).

16. 16. The filter material of any one of claims 1 to 15, comprising 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.

17. A segment comprising a filter material according to any one of claims 1 to 16 and a packaging material.

18. 18. The segment according to 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, particularly preferably at least 5 mm and at most 8 mm.

19. 19. The segment according to claim 17 or 18, having a length of at least 4 mm and at most 40 mm, preferably at least 6 mm and at most 35 mm, particularly preferably at least 10 mm and at most 28 mm.

20. 20. A segment according to any one of claims 17 to 19, having a resistance to attraction according to ISO 6565:2015 of at least 1 mm WG / mm and at most 12 mm WG / mm, preferably at least 2 mm WG / mm and at most 10 mm WG / mm.

21. 21. A segment according to any one of claims 17 to 20, having a packaging material formed from paper or foil.

22. At least 20 g / m ２ and a maximum of 150 g / m ２ , preferably at least 30 g / m ２ and a maximum of 130 g / m ２ 22. The segment of claim 17, having a packaging material with a basis weight of

23. 23. A segment according to any one of claims 17 to 22, comprising at least one capsule containing a fragrance.

24. A smoking article comprising a segment including an aerosol-forming material and a segment according to any one of claims 17 to 23.

25. 25. The smoking article of claim 24, wherein the smoking article is a filtered cigarette and the aerosol-forming material is formed from tobacco.

26. 25. The smoking article of claim 24, wherein the aerosol-forming material is only heated and not combusted during intended use.

27. 1. A process for producing a filter material for a smoking article, comprising the steps of: A - Providing a fiber web (4) comprising fibers selected from the group consisting of pulp fibers, fibers derived from regenerated cellulose, and mixtures thereof; B - Hydroentangling said fibrous web (4) by means of a plurality of water jets (11) directed onto said fibrous web; C - creating a wave-like structure in the nonwoven fabric (20, 30, 40) by means of a plurality of water jets (12) directed onto said fibrous web; D - Drying the hydroentangled nonwoven fabric (20, 30, 40); The proportion of the fibers in the fiber web in step A is selected so that these fibers together account for at least 50% and at most 100% of the mass of the hydroentangled nonwoven fabric (20, 30, 40) in a dry state from step D, the fiber web (4) provided in step A has a longitudinal direction which is the running direction of the fiber web, a transverse direction which is perpendicular to the longitudinal direction and extends within the plane of the fiber web, and a thickness direction which is perpendicular to the longitudinal direction and the transverse direction, and the water jets (12) directed onto the fiber web in step C are arranged so that the water jets (12) are spaced at least between each other. and the water jets are arranged such that the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven fabric (20, 30, 40) obtained in step D has a wave-like structure in the plane formed by the cross direction and the thickness direction, with a wave height (21, 31, 41) of at least 50 μm and at most 1000 μm, and a wavelength (22, 32, 42) of at least 150 μm and at most 5000 μm. process.

28. 28. Process according to claim 27, wherein the water jets (11, 11a, 12) for carrying out step B and / or step C are directed on both sides of the fibrous web.

29. 29. The process according to claim 27 or 28, wherein the water jets (12) in step C are positioned so that they strike areas forming wave troughs as viewed from each side.

30. In step C, the water jet (12) is at least 450 μm ２ and a maximum of 50,000 μm ２ 30. The process of any one of claims 27 to 29, wherein the fluid exits through an opening having an area of ​​0.05 .mu.m and which is preferably a circular opening.

31. 31. The process according to any one of claims 27 to 30, wherein the pressure of the water jets (12) in step C is at least 3 MPa and at most 40 MPa, and the pressure for generating the wavy structure is preferably selected depending on the speed of the fibrous web (4) such that the ratio p / v of the pressure p (MPa) to the speed v (m / s) of the fibrous web is 2.5≦p / v≦20, preferably 3≦p / v≦15.

32. 32. The process according to any one of claims 27 to 31, wherein the pressure of the water jet (11) in step B is at least 0.5 MPa and at most 60 MPa, preferably at least 1 MPa and at most 50 MPa, and wherein the pressure in step B is preferably selected depending on the velocity of the fibrous web (4) such that the ratio p / v between the pressure p (MPa) and the velocity v (m / s) of the fibrous web is 2≦p / v≦20, preferably 4≦p / v≦8.

33. 33. The process according to any one of claims 27 to 32, wherein the wave height (21, 31, 41) after step D is at least 100 μm and at most 900 μm, preferably at least 150 μm and at most 800 μm.

34. 34. The process according to any one of claims 27 to 33, wherein the wavelength (22, 32, 42) after step D is at least 300 μm and at most 4000 μm, preferably at least 500 μm and at most 2000 μm.

35. 35. The process according to any one of claims 27 to 34, wherein the hydroentangled nonwoven fabric (20, 30, 40) obtained in step D has any or any combination of the features defined in claims 1 to 16 for the hydroentangled nonwoven fabric (20, 30, 40) as a component of the claimed filter material.

36. In variant A1 of the process, the fibrous web (4) in step A is provided by a wet-laid process comprising the following substeps A1.1 to A1.3: A1.1 - Substep of preparing an aqueous suspension (1) comprising fibers selected from the group consisting of pulp fibers, fibers derived from regenerated cellulose, and mixtures thereof, the amount of fibers being selected so that these fibers together comprise at least 50% and at most 100% by mass of the hydroentangled nonwoven fabric (20, 30, 40) in the dry state from step D, A1.2 - the sub-step of applying said suspension (1) from step A1.1 to a running wire (3), and A1.3 - sub-step of dewatering said suspension (1) by means of a traveling wire (3) to form a fibrous web (4), The process preferably comprises a further sub-step A1.4: A1.4 - Substep of adjusting the moisture content of said fibrous web (4) by drying or wetting, 36. The process of any one of claims 27 to 35.

37. 37. The process according to claim 36, wherein the aqueous suspension (1) 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%, more particularly preferably at least 0.01% and at most 0.05%.

38. 38. The process according to claim 36 or 37, wherein the running wire (3) in steps A1.2 and A1.3 is inclined upward from the horizontal in the running direction of the fiber web (4) by an angle of at least 3° and at most 40°, preferably at least 5° and at most 30°, particularly preferably at least 15° and at most 25°.

39. 39. A process according to any one of claims 36 to 38, wherein in step A1.3 dewatering is assisted by creating a pressure difference between the two sides of the running wire (3), said pressure difference preferably being created by a vacuum box or by suitably shaped vanes.

40. 40. The process of any one of claims 36 to 39, wherein the drying in step A1.4 is performed by a heated drying cylinder or hot air and the wetting is performed by a spray bar.

41. In variant A2 of the process according to the invention, the fibrous web (4) in step A is provided by an airlaid process comprising the following substeps A2.1 and A2.2: A2.1 - Substep of producing a fibrous web by an airlaid process, wherein the fibrous web (4) comprises fibers selected from the group consisting of pulp fibers, fibers derived from regenerated cellulose, and mixtures thereof, the amount of these fibers being selected so that they together constitute at least 50% and at most 100% by mass of the hydroentangled nonwoven fabric (20, 30, 40) in the dry state from step D; and A2.2 - sub-step of wetting the fibrous web, 36. The process of any one of claims 27 to 35.

42. 42. The process of any one of claims 27 to 41, wherein the drying in step D is carried out at least in part by contact with hot air, by infrared radiation, or by microwave radiation, and wherein the drying in step D is preferably carried out by through-air drying.

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