Aerosol-generating items

Abstract

The present invention relates to a wrapper paper suitable for use in an aerosol-generating article, the wrapper paper comprising pulp fibers and a char-forming agent, wherein the pulp fibers constitute at least 70% and at most 95% by weight of the wrapper paper, and the char-forming agent is present in a concentration of at least 5% and at most 20% by weight of the wrapper paper, and the wrapper paper has a tensile strength R0 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 and a tensile strength R1 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 after being exposed to a temperature of 230°C for 1 minute. T The quotient r=R T / R0 is present in the wrapper paper in a concentration such that it is at least 0.20 and at most 0.90.

Description

[Technical Field]

[0001] The present invention relates to a wrapper paper for aerosol-generating articles that is relatively heat resistant, and therefore still has sufficient mechanical strength to allow the article to be handled without problems after use, and that has a flame retardant effect so that the aerosol-generating article made from the wrapper paper cannot be smoked like a smoking article, which is achieved by the high content of specific char-forming agents in the wrapper paper. [Background technology]

[0002] In the prior art, aerosol-generating articles are known that include an aerosol-generating material and a paper that encases the aerosol-generating material, typically forming a cylindrical rod. In this regard, the aerosol-generating material is a material that releases an aerosol when heated, and the aerosol-generating material is only heated and does not burn. In many cases, the aerosol-generating article also includes a filter, which can filter components of the aerosol, and is encased in a filter wrapper paper and an additional wrapper paper that binds the filter and the encased rod together with the aerosol-generating material.

[0003] During the intended use of an aerosol-generating article, the aerosol-generating material typically heats but does not burn. This heating can be accomplished, for example, by an external device into which the aerosol-generating article is inserted, or by a heat source attached to one end of the aerosol-generating article that is activated by ignition to use the article. During heating of the aerosol-generating material, the wrapper paper also heats and thermally degrades. This can cause the wrapper paper to lose significant strength, resulting in tearing during removal of the aerosol-generating article from the heating device. This is undesirable because it requires additional cleanup by the consumer. Additionally, in aerosol-generating articles with an integrated heat source, the wrapper paper can lose its strength during heating, causing the heat source to fall and pose a fire hazard.

[0004] Furthermore, it is desirable to prevent consumers from inadvertently using the aerosol-generating article in the same manner as a cigarette and attempting to light the end of the aerosol-generating article so as to initiate the combustion or smoking process of the aerosol-generating material. Therefore, the wrapper paper of the aerosol-generating article should be flame-retardant.

[0005] Attempts to make wrappers for such aerosol-generating articles heat or flame resistant have been only partially successful.

[0006] For example, WO 2015 / 082648 describes a wrapper paper that is composed of relatively few pulp fibers and is coated with a calcium carbonate and binder composition such that at least 50% of the wrapper paper is formed by calcium carbonate. A disadvantage of this wrapper paper is that the thick coating makes it relatively fragile, generating a lot of dust during the production of aerosol-generating articles from the wrapper paper. Furthermore, due to the low fiber content, the tensile strength is not particularly high.

[0007] WO 2011 / 117750 describes a wrapper paper consisting of a laminate of aluminum foil and paper. The aluminum foil faces the aerosol-generating material and partially protects the paper from the effects of heat. The disadvantages of this wrapper paper are its complicated manufacturing process and its low biodegradability, since experience has shown that many aerosol-generating articles are simply discarded in the environment after use.

[0008] Therefore, there is an interest in having available a wrapper paper that still has sufficient tensile strength after heating, has flame retardant effect, and is nevertheless biodegradable. Furthermore, the design of a wrapper paper for an aerosol-generating article needs to take into account, among other things, the regulatory, toxicological, and taste impact of the wrapper paper on the aerosol-generating article. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2015 / 082648 [Patent Document 2] International Publication No. 2011 / 117750 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a wrapper paper for aerosol-generating articles that is inherently heat or flame resistant and has advantageous properties such as strength, processability, biodegradability, and taste impact.

[0011] An aerosol-generating article in the context of the present invention is a rod-shaped article comprising an aerosol-generating material and a wrapper paper enclosing the aerosol-generating material, wherein during intended use the aerosol-generating material is heated but not combusted, which occurs in any case with typical aerosol-generating materials, such as tobacco, when the aerosol-generating material is heated to temperatures of up to 400°C. [Means for solving the problem]

[0012] This object is achieved by a wrapper paper for an aerosol-generating article according to claim 1, an aerosol-generating article comprising this wrapper paper according to claim 24, the use of such a wrapper paper for an aerosol-generating article according to claim 26, and a method for producing a wrapper paper according to the invention according to claim 27. Further advantageous embodiments are provided in the dependent claims.

[0013] The inventors have discovered that this object can be achieved by providing a wrapper paper suitable for use in an aerosol-generating article, the wrapper paper comprising pulp fibers and a char-forming agent, wherein the pulp fibers constitute at least 70% and at most 95% by weight of the wrapper paper, and the char-forming agent is present in a concentration of at least 5% and at most 20% by weight of the wrapper paper, and the wrapper paper has a tensile strength R0 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 and a tensile strength R1 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 after being exposed to a temperature of 230°C for 1 minute. T The quotient r=R T It has been found that this can be achieved by the wrapper paper being contained in the wrapper paper at a concentration such that / R0 is at least 0.20 and at most 0.90.

[0014] According to the inventors' findings, a high pulp fiber content is necessary to obtain high initial strength in wrapper paper. Many char-forming agents that could potentially be used in paper are known to damage the pulp fibers in the paper, rapidly leading to substantial loss of strength when heated. However, they protect the pulp fibers further present in the paper structure from thermal degradation. Because paper is generally prone to combustion, it is generally assumed that a very high concentration of char-forming agents must be used in paper for effective flame retardancy. However, common assumptions and the inventors' experiments have shown that at this concentration, the pulp fibers are damaged so greatly that the strength is reduced so significantly that their use cannot be reasonably considered.

[0015] In contrast, the present inventors have found that for a few char-forming agents, there is in fact a suitable narrow range of concentrations within which there is good flame retardant effect and the paper strength is not significantly reduced.

[0016] Only the combination of a high pulp fiber content and a suitably selected concentration of char-forming agent allows the production of a wrapper paper that, due to its high initial strength and despite the loss of strength due to the char-forming agent, also has such high tensile strength after heating that an aerosol-generating article made from the wrapper paper can be removed from the heating device without any problems or risk of the heat source incorporated in the aerosol-generating article falling, and furthermore, the flame retardant effect is sufficient so that the aerosol-generating article cannot be smoked like a cigarette.

[0017] Additionally, the components of the wrapper paper provide excellent biodegradability and very good processability during the manufacture of the aerosol-generating article.

[0018] For its strength, the wrapper paper requires pulp fibers to constitute at least 70% and at most 95% of the mass of the wrapper paper. To obtain an even better ratio between pulp fibers and char-forming agent, the proportion of pulp fibers can be preferably at least 75% and at most 90%, particularly preferably at least 80% and at most 90%, respectively, based on the mass of the wrapper paper.

[0019] The pulp fibers are preferably sourced from one or more plants selected from the group consisting of conifers, deciduous trees, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, abaca, sisal, kenaf and cotton. The pulp fibers may also be formed wholly or partly by fibers from regenerated cellulose, such as Tencel® fibers, Lyocell® fibers, viscose fibers or Modal® fibers.

[0020] Preferably, the pulp fibers are formed from pulp fibers of softwood origin in a proportion of at least 40% and at most 100% by mass of the pulp fibers, since these pulp fibers provide the wrapper paper with high strength.

[0021] The wrapper paper contains a char-forming agent that constitutes at least 5% and at most 20% of the mass of the wrapper paper. According to the inventors' findings, the char-forming agent protects the pulp fibers within the paper structure from excessive oxidation, but also damages the pulp fibers itself, so the concentration of the char-forming agent must be within a narrow range and depends on the type of char-forming agent. As the concentration of the char-forming agent increases, the flame retardant effect becomes stronger, but the strength of the wrapper paper after heating decreases due to increased damage to the pulp fibers. Therefore, the proportion of the char-forming agent in the wrapper paper is preferably at least 9% and at most 16% of the mass of the wrapper paper.

[0022] Preferably, the char-forming agent is ammonium phosphate, particularly preferably monoammonium phosphate, diammonium phosphate, triammonium phosphate, or ammonium polyphosphate, or a mixture thereof. Less preferred char-forming agents are guanylurea phosphate, guanidine phosphate, phosphoric acid, phosphonates, melamine phosphate, dicyandiamide, boric acid, or borax. These less preferred compounds are more difficult to process or are not entirely toxicologically problem-free. Sodium polyphosphate is also a char-forming agent, but is not included in the present invention.

[0023] The choice of the concentration of the char-forming agent is not free within the range provided, but depends on the type of char-forming agent and must be selected so as not to cause too great a loss in the strength of the wrapper paper after heating.

[0024] For this purpose, the tensile strength of the wrapper paper in the machine direction is determined as a characteristic property of strength, first under the conditions of ISO 187:1990 and then after heating the wrapper paper. More precisely, it can be determined in the following way:

[0025] First, a paper sample of suitable shape, typically a 15 mm wide strip, is prepared according to ISO 187:1990 and tested in a tensile test according to ISO 1924-2:2008. The tensile strength depends on the direction in which the paper sample is taken. Here, the tensile strength should always be understood to be the tensile strength in the running direction of the wrapper paper during paper production, the so-called machine direction.

[0026] The initial tensile strength, denoted by R0, is determined according to the present invention by conditioning a paper sample according to ISO 187:1990 without any preceding heat load and testing it according to ISO 1924-2:2008. The tensile strength after heat load R T is determined by exposing the sample to a temperature of 230°C in air for 1 minute, allowing air to reach essentially all sides of the paper sample and with low airflow. The paper sample is then conditioned according to ISO 187:1990 and the tensile strength is determined according to ISO 1924-2:2008. The quotient r = R T The quotient r / R0 represents the percentage of tensile strength remaining after the wrapper paper is thermally loaded and therefore characterizes the thermal resistance of the wrapper paper. A high value of the quotient r indicates a high thermal resistance. According to the present invention, the concentration of the char-forming agent in the wrapper paper determines the tensile strength R after the thermal load. T The quotient r between the initial tensile strength R0 and the tensile strength (at 230°C for 1 minute) should be selected to be at least 0.20 and at most 0.90, particularly preferably at least 0.25 and at most 0.80. This means that the tensile strength does not decrease by more than 80%.

[0027] The quotient can be affected by the amount of pulp fiber and the type and concentration of char-forming agent, with more pulp fiber leading to a higher initial tensile strength R0, and an increase in the concentration of char-forming agent generally leading to a lower heat load R0. T This leads to a decrease in the tensile strength after the test. TThe negative effect of the char-forming agent on the flame retardancy must be balanced with the better flame retardancy effect that accompanies increasing concentrations, based on the type of use of the aerosol-generating article. It has been found that within the ranges according to the present invention and the preferred ranges of char-forming agent concentrations, a very good compromise can be found for aerosol-generating articles.

[0028] Preferably, the tensile strength R T should not fall below a certain value after the thermal load to ensure that the aerosol-generating article can be handled without problems during and after use. Preferably, the tensile strength R of the wrapper paper in the machine direction after the thermal load T is at least 8 N / 15 mm and at most 50 N / 15 mm, particularly preferably at least 10 N / 15 mm and at most 40 N / 15 mm.

[0029] According to the inventors' findings, it is important to know how the char-forming agent is distributed throughout the thickness of the wrapper paper. Generally, a good flame retardant effect can be achieved when the char-forming agent is distributed essentially uniformly throughout the wrapper paper. However, in a preferred embodiment, the wrapper paper is designed so that the side of the wrapper paper facing the aerosol-generating material contains a higher proportion of char-forming agent than the other side of the wrapper paper. The side facing the aerosol-generating material is typically exposed to a higher thermal load. Therefore, a higher content of char-forming agent on this side of the wrapper paper can contribute particularly well to the flame retardant effect. In this way, the proportion of char-forming agent in the wrapper paper can be reduced without loss of flame retardant effect, allowing the proportion of pulp fiber in the wrapper paper to be increased at the same basis weight, resulting in an overall increase in the strength of the wrapper paper. Alternatively, with this favorable distribution of the char-forming agent in the wrapper paper, the basis weight can also be reduced without loss of flame retardant effect, thereby reducing material requirements.

[0030] The distribution of the char-forming agent in the wrapper paper can be affected by the manufacturing method, as further explained below.

[0031] Preferably, the char-forming agent is distributed essentially uniformly over at least 70% of the surface area of ​​the wrapper paper, and particularly preferably over at least 95% of the surface area, with variations in the proportion of char-forming agent within these surface areas occurring only through manufacturing and not intended.

[0032] A drawback of char-forming agents can be that they discolor the wrapper paper, darkening it under thermal stress. This drawback can be overcome by combining the wrapper paper according to the invention with an additional paper layer, for example by gluing, so that the wrapper paper according to the invention faces the aerosol-generating material and the additional paper layer is located on the side opposite the aerosol-generating material. Under thermal stress, this additional paper layer covers the wrapper paper, so that the color visible from the outside does not change, or changes only slightly.

[0033] Therefore, preferably, the wrapper paper is combined with a paper layer. Particularly preferably, this paper layer comprises pulp fibers and calcium carbonate particles, the calcium carbonate particles constituting at least 15% and at most 40% of the paper layer's mass. The calcium carbonate particles impart a white color and high opacity to the paper layer, so that discoloration of the underlying wrapper paper according to the present invention is not visible or only slightly visible. It should be noted that a wrapper paper comprising an additional paper layer as a whole could also be described as a "two-ply wrapper paper," but this designation will be avoided here. Instead, in the language of this disclosure, such a two-ply structure will be referred to as a "wrapper paper comprising an additional paper layer," since only the part of the two-ply structure referred to as "wrapper paper" needs to meet the above requirements regarding pulp fibers, char-forming agent, and tensile strength quotient.

[0034] In addition to the pulp fibers and char-forming agents, the wrapper paper according to the present invention may contain further ingredients, such as fillers, sizing agents, wet strength agents, additives, processing aids, humectants, and flavoring agents. Those skilled in the art can select these ingredients based on their experience. In particular, wet strength agents may be useful for use in aerosol-generating articles because the aerosol formed during use of the aerosol-generating article has a high moisture content. The wrapper paper can absorb water from the aerosol, resulting in a loss of its strength. This can be prevented by using a wet strength agent.

[0035] The filler material in the wrapper paper can contribute to reducing discoloration of the wrapper paper.However, the filler material also reduces the tensile strength of the wrapper paper, so its proportion should not be too high.Therefore, the proportion of the filler material in the wrapper paper is preferably at least 0% and at most 20%, particularly preferably at least 0% and at most 10%, in particular at least 0% and at most 5%, based on the mass of the wrapper paper.

[0036] The filler material is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talcum, and mixtures thereof. Less preferably, the filler material is a carbonate.

[0037] In a preferred embodiment, the wrapper paper further comprises starch or a starch derivative or is coated with starch or a starch derivative. The proportion of starch or starch derivative in this preferred embodiment is at least 2% and at most 10% by mass of the wrapper paper. This preferred embodiment offers an additional advantage of resistance to oil penetration. The aerosol-generating material may contain oils, such as flavorings, that penetrate the wrapper paper and cause staining during storage or use of the aerosol-generating article. Resistance to oil penetration can be determined according to TAPPI T559 cm-12 and is given as a KIT level. In this preferred embodiment, the KIT level is at least 4 and at most 8.

[0038] The basis weight of the wrapper paper can vary, with higher basis weight generally also meaning higher tensile strength. However, at higher basis weights the wrapper paper becomes stiffer, more difficult to process and increases material requirements. Therefore, preferably the basis weight of the wrapper paper according to the present invention is at least 15 g / m 2 and up to 80 g / m 2 , particularly preferably at least 20 g / m 2 and up to 60 g / m 2 The basis weight of the wrapper paper can be determined according to ISO 536:2019.

[0039] The thickness of the wrapper paper mainly affects the bending stiffness and heat transfer within the wrapper paper. A high bending stiffness is advantageous because the aerosol-generating article made from the wrapper paper will then be less deformed, but on the other hand, a high bending stiffness may cause problems due to the restoring forces when the aerosol-generating material is wrapped in the wrapper paper. A high thickness slows down the heat transfer through the wrapper paper and is also advantageous for this reason. Preferably, the thickness of the wrapper paper according to the present invention is at least 25 μm and at most 100 μm, particularly preferably at least 40 μm and at most 80 μm. The thickness can be determined for a single layer according to ISO 534:2011.

[0040] The initial tensile strength R0 of the wrapper paper measured in the machine direction is preferably at least 10 N / 15 mm and at most 100 N / 15 mm, particularly preferably at least 20 N / 15 mm and at most 80 N / 15 mm. A high proportion of pulp fibers results in a high tensile strength. However, this also means higher material requirements, for which reason it is unwise to aim for a particularly high tensile strength. The preferred range allows for a particularly advantageous combination of problem-free processability and material requirements. Tensile strength can be determined in accordance with ISO 1924-2:2008.

[0041] Because aerosol-generating materials often contain humectants, the aerosol generated during heating has a relatively high moisture content. This moisture can reduce the strength of the wrapper paper, and for that reason, it is advantageous for the wrapper paper to also have a suitable wet strength. Therefore, the longitudinal wet strength is preferably at least 1 N / 15 mm and at most 10 N / 15 mm, particularly preferably at least 2 N / 15 mm and at most 8 N / 15 mm. Wet strength can be determined in accordance with ISO 12625-5:2016.

[0042] The air permeability of the wrapper paper can be reduced. Low air permeability is often achieved by more highly refined pulp fibers. This also contributes to improved strength, so the air permeability is preferably at least 0 cm 3 / (cm 2 ·min·kPa) and up to 50cm 3 / (cm 2 ·min ·kPa), particularly preferably at least 0 cm 3 / (cm 2 ·min·kPa) and up to 20cm 3 / (cm 2 ·min·kPa). Air permeability can be measured according to ISO 2965:2019.

[0043] When the wrapper paper according to the present invention is visible from the outside of the aerosol-generating article, optical properties can be important. Generally, high opacity and high brightness are desired. Both properties can be substantially affected by the type and amount of filler material in the wrapper paper. Preferably, the opacity is at least 40% and at most 90%, particularly preferably at least 45% and at most 80%. Preferably, the brightness is at least 80% and at most 95%, particularly preferably at least 83% and at most 90%.

[0044] Aerosol-generating articles can be produced from the wrapper paper according to the invention according to methods known in the art. Thus, an aerosol-generating article according to the invention comprises an aerosol-generating material and a wrapper paper according to one of the above-described embodiments, the wrapper paper enclosing the aerosol-generating material.

[0045] In a preferred embodiment of the aerosol-generating article, the proportion of the char-forming agent is higher on one side of the wrapper paper than on the other side, the side with the higher proportion of char-forming agent facing the aerosol-generating material.

[0046] The wrapper paper according to the invention can be advantageously used in aerosol-generating articles, and for that reason the use of the wrapper paper according to the invention in aerosol-generating articles is also an object of the present invention.

[0047] The wrapper paper according to the present invention can be produced according to the following method according to the present invention, the method comprising steps A to G: A - suspending pulp fibers in an aqueous suspension; B—purifying the suspended pulp fibers in a refining unit; C—applying the suspension to the running wire; D—forming a fibrous web by dewatering the suspension; E—pressing the fiber web; F—Drying the fiber web; G - Rolling up the wrapper paper; and between step F and step G, applying at least one composition containing a char-forming agent to the fibrous web and drying the fibrous web to form said wrapper paper, wherein the wrapper paper from step G comprises pulp fibers and the char-forming agent, the pulp fibers comprising at least 70% and at most 95% by weight of the wrapper paper, the char-forming agent comprising at least 5% and at most 20% by weight of the wrapper paper, and the char-forming agent has a tensile strength R0 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 and a tensile strength R1 measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 after exposing the wrapper paper to a temperature of 230°C for 1 minute. T The quotient r=R T The wrapper paper is contained in a concentration such that / R0 is at least 0.20 and at most 0.90.

[0048] Preferably, the step of applying the composition containing the char-forming agent to the fibrous web is carried out by one or a combination of two or more of the following steps:

[0049] F.1 Application of a composition containing a char-forming agent to a fibrous web in the size press of a paper machine; F.2 Single-sided application of a composition containing a char-forming agent to a fibrous web in the film press or coating unit of a paper machine; and F.3 Single-sided application of a composition containing a char-forming agent to a fibrous web by printing, especially rotogravure printing or spraying.

[0050] In this respect, step F.1 is carried out in a size press, so that the fibrous web is impregnated with the composition containing the char-forming agent. This variant offers the advantage that it is easy to carry out. This advantage generally leads to a substantially uniform distribution of the char-forming agent throughout the thickness of the wrapper paper, so that a relatively large amount of char-forming agent is required to achieve the desired effect. However, in practice, it is also possible to adjust the settings of the size press in this step, so that the char-forming agent is distributed unevenly throughout the thickness of the fibrous web, and thus the wrapper paper.

[0051] According to step F.2, a composition containing a char-forming agent is applied to one side of the fibrous web in a film press or coating unit, which results in a non-uniform distribution of the char-forming agent throughout the thickness of the wrapper paper, allowing for a lower proportion of char-forming agent in the wrapper paper to achieve a high flame retardant effect.

[0052] According to step F.3, the composition containing the char-forming agent is applied to one side of the fibrous web by printing or spraying; in a particularly preferred embodiment, the composition is printed on one side of the fibrous web by a rotary gravure printing unit. In this regard, the fibrous web is preferably dried, wound up, and unwound again before step F.3. The fibrous web can then be transported in the wound state to a further device, where the composition can be applied by printing or spraying. Steps F.1 and F.2 can in principle be carried out on the same paper machine as the wrapper paper is produced, while the application according to step F.3 is usually carried out on a separate device.

[0053] In a very particularly preferred embodiment, steps F.1 and F.3 are combined, so that first in step F.1 the fibrous web is impregnated with a composition containing a char-forming agent in a size press, and in step F.3 a further composition containing a char-forming agent is printed on one side of the fibrous web in a rotogravure printing unit. In this very particularly preferred embodiment, the char-forming agent is distributed in the wrapper paper and is present in a higher concentration on one side of the wrapper paper, so that the flame retardant effect can be significantly further enhanced.

[0054] In a further very particularly preferred embodiment, steps F.1 and F.2 are combined, with step F.1 taking place in a size press and step F.2 taking place in a coating unit. In this very particularly preferred embodiment, the wrapper paper can be produced particularly efficiently, since for example all coating devices can be integrated into one paper machine.

[0055] Regardless of whether one or more of steps F.1, F.2 or F.3 are used, the composition containing the char-forming agent is preferably applied to at least 70% of the surface area of ​​the wrapper paper, particularly preferably to at least 95% of the surface area of ​​the wrapper paper.

[0056] The composition used in steps F.1, F.2, or F.3 contains a char-forming agent and a solvent, preferably water. The amount of char-forming agent in the composition can vary and depends on the type of application method, the amount applied, and the desired amount of char-forming agent in the wrapper paper. Those skilled in the art can determine a suitable composition with these considerations in mind and design their application method accordingly.

[0057] In a very particularly preferred embodiment, one of steps F.1 and F.2 is carried out, then the fibrous web is dried, rolled up and unrolled again, and then step F.3 is carried out, the dried rolled-up fibrous web before step F.3 preferably containing a char-forming agent in an amount of at least 5% and at most 10% by weight of this dried rolled-up fibrous web.

[0058] When steps F.1, F.2 and / or F.3 are combined in any manner, the compositions containing the char-forming agent applied in steps F.1, F.2 and / or F.3 can be different.

[0059] In the wrapper paper after step G, the pulp fibers constitute at least 70% and at most 95% of the mass of the wrapper paper. To obtain an even better ratio between pulp fibers and char-forming agent, the proportion of pulp fibers can be preferably at least 75% and at most 90%, particularly preferably at least 80% and at most 90%, respectively, relative to the mass of the wrapper paper after step G.

[0060] The pulp fibers of step A are preferably sourced from one or more plants selected from the group consisting of conifers, deciduous trees, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, abaca, sisal, kenaf and cotton. The pulp fibers may also be formed wholly or partly by fibers made from regenerated cellulose, such as Tencel® fibers, Lyocell® fibers, viscose fibers or Modal® fibers.

[0061] Preferably, the pulp fibers in step A are formed by pulp fibers of softwood origin in a proportion of at least 40% and up to 100% by mass of the pulp fibers, since these pulp fibers provide a wrapper paper in step G with high initial strength.

[0062] The wrapper paper after step G comprises a char-forming agent that constitutes at least 5% and at most 20% of the mass of the wrapper paper. Preferably, the proportion of char-forming agent in the wrapper paper after step G is at least 9% and at most 16% of the mass of the wrapper paper.

[0063] Preferably, the char-forming agent is ammonium phosphate, particularly preferably monoammonium phosphate, diammonium phosphate, triammonium phosphate, or ammonium polyphosphate, or a mixture thereof. Less preferred char-forming agents are guanylurea phosphate, guanidine phosphate, phosphoric acid, phosphonates, melamine phosphate, dicyandiamide, boric acid, or borax. These less preferred compounds are more difficult to process or are not entirely toxicologically problem-free. Sodium polyphosphate is also a char-forming agent, but is not included in the present invention.

[0064] In a preferred embodiment, after step G the wrapper paper is a wrapper paper according to one of the previous embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0065] Some preferred embodiments of the wrapper paper according to the present invention will now be described.

[0066] The wrapper paper P1 according to the invention was produced on a Fourdrinier paper machine. For this purpose, pulp fibers were suspended in water (step A) and refined in a refining unit (step B). The suspension was then applied to a running wire (step C) where it was dewatered to form a fibrous web (step D). The fibrous web was pressed for further dewatering (step E) and dried by contact with heated drying cylinders (step F). In the size press of the paper machine, the entire surface of the fibrous web was impregnated with a composition comprising water and monoammonium phosphate (step F.1), and the fibrous web was then dried by contact with heated drying cylinders. Finally, the fibrous web was rolled up (step G), yielding the wrapper paper P1 according to the invention.

[0067] The amount of pulp fiber was selected so that wrapper paper P1 comprised about 87% pulp fiber by mass. The composition of step F.1 comprised water and monoammonium phosphate and was selected together with the size press settings so that the amount of monoammonium phosphate in the wrapper paper after step G was about 7%. It can be assumed that the distribution of monoammonium phosphate in wrapper paper P1 through its thickness was essentially uniform.

[0068] The wrapper paper P2 according to the invention was produced from the wrapper paper P1 according to the invention by unwinding the wrapper paper P1 from a reel and printing a composition comprising water and monoammonium phosphate all over one side of the wrapper paper in a rotogravure printing unit (step F.3). The wrapper paper was then dried by hot air drying and rewound (step G). The composition of step F.3 was selected together with the settings of the rotogravure printing unit, and in particular the geometry of the printing cylinder, so that in the finished wrapper paper P2 a total of 12.5% ​​of the wrapper paper mass was formed by monoammonium phosphate. In this way, a non-uniform distribution of monoammonium phosphate in the wrapper paper was obtained, with a higher monoammonium phosphate content on the printed side than on the other side.

[0069] In wrapper paper P2, 82% of the mass was formed by pulp fibers.

[0070] A wrapper paper Z1 not according to the invention, containing 70% pulp fibre and 29% precipitated calcium carbonate but no char-forming agent, was used as a comparison.

[0071] In addition, it contains 90% pulp fiber and 10% sodium polyphosphate (NaPO3) n A wrapper paper Z2 not according to the invention, containing as a char-forming agent, was used as a comparison example.

[0072] To obtain a further wrapper paper P3, a wrapper paper Z1 not according to the invention was glued to a wrapper paper P2 according to the invention, with the side of wrapper paper P2 having a higher monoammonium phosphate content facing away from wrapper paper Z1 to form a two-layer structure.

[0073] The data for the wrappers P1 and P2 according to the invention, the two-ply structure P3 and the comparative examples Z1 and Z2 not according to the invention were determined according to the usual criteria.

[0074] Heat load R TTo determine the subsequent tensile strength, wrapper papers P1, P2, P3 and Z1, Z2 were placed for 1 minute in a drying oven heated to 230° C. They were then conditioned according to ISO 187:1990 and the tensile strength was measured according to ISO 1924-2:2008.

[0075] To characterize the thermal resistance, the initial tensile strength R0 and the tensile strength R after thermal loading are T quotient r=R T / R0 was calculated.

[0076] All data for wrappers P1, P2, P3 and Z1, Z2 can be found in Table 1.

[0077] [Table 1]

[0078] Table 1 shows that for wrapper papers P1 and P2 according to the invention, and for two-ply structure P3 comprising wrapper paper P2 according to the invention, heat stress reduces the tensile strength by 34% to 55%. For comparative example Z1, which does not contain a char-forming agent, the tensile strength is barely reduced by heat stress and is still about 94% of the initial tensile strength. For comparative example Z2, which does not contain sodium polyphosphate as a char-forming agent, the tensile strength after heat stress is only about 19% of the initial tensile strength, and the absolute value of 6.3 N / 15 mm is too low to allow aerosol-generating articles made from the wrapper papers to be safely removed from the heating appliance after use.

[0079] The wrappers P1 and P2 according to the invention and the two-ply structure P3 all show an acceptable decrease in tensile strength, but it is noteworthy that the higher content of monoammonium phosphate in wrapper paper P2 compared to wrappers P1 and P2 according to the invention damages the fibers more and causes a more severe decrease in tensile strength after thermal loading.

[0080] In addition to an insufficient decrease in tensile strength, flame-retardant effectiveness is also important. To test for flame-retardant effectiveness, aerosol-generating articles intended for use in heating appliances were produced from wrapper papers P1 / P2 according to the present invention, two-layer structure P3, and comparative examples Z1 and Z2 not according to the present invention. The production of the aerosol-generating articles was problem-free for all wrapper papers. When attempting to light the aerosol-generating articles, such as cigarettes, with a lighter, it was immediately apparent that comparative example Z1 not according to the present invention had no flame-retardant effect. The aerosol-generating articles produced from the wrapper papers could be ignited without any problems. Despite the longer application of the lighter flame, the aerosol-generating articles with wrapper papers P1 / P2 according to the present invention, two-layer structure P3, and comparative example Z2 not according to the present invention could not be ignited to initiate a combustion or stable smoking process. It was also impossible to smoke these aerosol-generating articles according to a standardized process. In terms of flame retardant effect, the wrapper paper P2 according to the invention was found to be slightly better than P1, indicating that the non-uniform distribution of the char-forming agent throughout the thickness of the wrapper paper may contribute to the improved flame retardant effect.

[0081] The two-layer structure P3 is a laminate of a wrapper paper P2 according to the invention and a comparative example Z1 not according to the invention, and after use, the aerosol-generating article made from the wrapper paper showed significantly less discoloration than the aerosol-generating article made from P1 and P2, whereby the wrapper paper Z1 serves to hide the discoloration of the wrapper paper P2.

[0082] No effect on the taste of the aerosol-generating product was observed.

[0083] Thus, the wrapper paper according to the present invention is very well suited for use in aerosol-generating articles, having a better combination of strength and flame retardant effectiveness after heating than comparable wrapper papers of the prior art, along with good biodegradability.

Claims

1. An aerosol-generating article comprising a wrapper paper and an aerosol-generating material, wherein the aerosol-generating material is heated but not combusted during intended use of the aerosol-generating article, and the wrapper paper encases the aerosol-generating material; The wrapper paper comprises pulp fibers and a char-forming agent, the pulp fibers constituting at least 70% and at most 95% by mass of the wrapper paper, and the char-forming agent is contained in a concentration of at least 5% and at most 20% by mass of the wrapper paper, and has a tensile strength R of at least 70% and at most 95% by mass of the wrapper paper, the char-forming agent being an initial tensile strength measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990. ０ and the tensile strength R, which is the tensile strength after heat load measured according to ISO 1924-2:2008 under the conditions of ISO 187:1990 after the wrapper paper has been exposed to a temperature of 230°C for 1 minute. Ｔ The quotient r = R Ｔ / R ０ is present in said wrapper paper at a concentration such that is at least 0.20 and at most 0.

90.

2. 2. The aerosol-generating article of claim 1, wherein the proportion of pulp fibers in the wrapper paper is at least 75% and at most 90%, respectively, based on the mass of the wrapper paper.

3. 3. The aerosol-generating article of claim 1 or 2, wherein the pulp fibers are supplied in whole or in part from one or more plants selected from the group consisting of conifers, deciduous trees, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, abaca, sisal, kenaf, and cotton.

4. 4. An aerosol-generating article according to claim 1 , wherein the pulp fibres are formed wholly or partly by fibres from regenerated cellulose, in particular Tencel® fibres, Lyocell® fibres, Viscose fibres or Modal® fibres.

5. 5. The aerosol-generating article according to claim 1, wherein the pulp fibres are sourced from softwood in a proportion of at least 40% and at most 100% by mass of the pulp fibres.

6. 6. An aerosol-generating article according to any one of claims 1 to 5, wherein the proportion of char-forming agent in the wrapper paper constitutes at least 9% and at most 16% by mass of the wrapper paper.

7. 7. The aerosol-generating article of claim 1, wherein the char-forming agent is ammonium phosphate, or the char-forming agent is at least partially formed by guanylurea phosphate, guanidine phosphate, phosphoric acid, phosphonate, melamine phosphate, dicyandiamide, boric acid, or borax.

8. The tensile strength R of the wrapper paper after the wrapper paper is exposed to a temperature of 230°C for 1 minute Ｔ 8. An aerosol-generating article according to any one of claims 1 to 7, wherein the elastic modulus is at least 8 N / 15 mm and at most 50 N / 15 mm.

9. 9. The aerosol-generating article of claim 1, wherein the side of the wrapper paper that faces the aerosol-generating material during intended use contains a higher proportion of char-forming agent than the other side of the wrapper paper.

10. 10. The aerosol-generating article of any one of claims 1 to 9, wherein the char-forming agent is at least substantially uniformly distributed over at least 70% of the surface area of ​​the wrapper paper.

11. 11. An aerosol-generating article according to any one of claims 1 to 10, wherein the wrapper paper is combined with a further paper layer, in particular by gluing, such that the wrapper paper according to the invention faces the aerosol-generating material during the intended use, and the further paper layer is arranged on a side facing away from the aerosol-generating material.

12. 12. The aerosol-generating article of claim 11, wherein the further paper layer comprises pulp fibers and calcium carbonate particles, the calcium carbonate particles comprising at least 15% and at most 40% by mass of the further paper layer.

13. 13. The aerosol-generating article of any one of claims 1 to 12, wherein the wrapper paper further comprises at least one additional ingredient selected from the group consisting of filler materials, sizing agents, wet strength agents, additives, processing aids, humectants, and flavoring agents.

14. 14. The aerosol-generating article of claim 13, wherein the proportion of the filler material is at least 0% and at most 20% by weight of the wrapper paper, respectively.

15. 15. The aerosol-generating article of claim 13 or 14, wherein the filler material is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium dioxide, magnesium hydroxide, aluminum hydroxide, kaolin, talcum, and mixtures thereof.

16. 16. An aerosol-generating article according to any one of claims 1 to 15, wherein the wrapper paper contains or is coated with starch or a starch derivative, the proportion of the starch or starch derivative being at least 2% and at most 10% by mass of the wrapper paper.

17. 17. An aerosol-generating article according to any one of claims 1 to 16, wherein the wrapper paper has a KIT level, determined according to TAPPI T559cm-12, of at least 4 and at most 8.

18. The wrapper paper has a thickness of at least 15 g / m ２ and a basis weight of up to 80 g / m 2 .

19. 19. An aerosol-generating article according to any one of claims 1 to 18, wherein the wrapper paper has a thickness of at least 25 μm and at most 100 μm.

20. The wrapper paper has a tensile strength R before thermal loading measured in the machine direction of at least 10 N / 15 mm and at most 100 N / 15 mm. ０ The aerosol-generating article according to any one of claims 1 to 19, comprising:

21. An aerosol-generating article described in any one of claims 1 to 20, having a wet strength in the longitudinal direction according to ISO 12625-5:2016 of at least 1 N / 15 mm and at most 10 N / 15 mm.

22. The wrapper paper is at least 0 cm ３ / (cm ２ min kPa) and up to 50 cm ３ / (cm ２ 22. The aerosol-generating article according to any one of claims 1 to 21, having an air permeability of 0.05 psi (0.05 psi).

23. 23. An aerosol-generating article according to any one of claims 1 to 22, wherein the wrapper paper has an opacity of at least 40% and at most 80% and / or a brightness of at least 80% and at most 95%.

24. 24. The aerosol-generating article of any one of claims 1 to 23, wherein the proportion of char-forming agent is higher on one side of the wrapper paper than on the other side, the side with the higher proportion of char-forming agent facing the aerosol-generating material.

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