Heat-resistant packaging paper for aerosol-generating products

Abstract

The present invention relates to a wrapping paper suitable for use on an aerosol generating article and comprising pulp fibers and a char-forming agent, wherein the pulp fibers account for at least 70% and at most 95% of the mass of the wrapping paper, and the char-forming agent is contained in a concentration of at least 5% and at most 20% relative to the mass of the wrapping paper and is present in the wrapping paper in such a concentration that the tensile strength R measured under the conditions of ISO 187:1990 according to ISO 1924-2:2008 is less than or equal to 10%. 0 The tensile strength R measured according to ISO 1924-2:2008 under the conditions of ISO 187:1990 after the wrapper has been exposed to a temperature of 230°C for a period of 1 minute T The quotient r = R T / R 0 is at least 0.20 and at most 0.90.

Description

Field of the Invention

[0001] The present invention relates to a wrapper for an aerosol-generating article, which has a high heat resistance and, therefore, after use of the article, still has sufficient mechanical strength to ensure problem-free handling of the article, and additionally has a flame retardant effect, so that an aerosol-generating article made from the wrapper cannot be smoked like a smoking article. This is achieved by a high content of a specific char-forming agent in the wrapper.

[0002] Background and Prior Art

[0003] In the prior art, aerosol-generating articles are known, which include an aerosol-generating material and a paper, which wraps the aerosol-generating material and thereby forms a rod that is generally cylindrical. In this regard, the aerosol-generating material is a material that releases an aerosol when heat is applied, wherein the aerosol-generating material is only heated but not burned. In many cases, the aerosol-generating article also includes a filter, which can filter components of the aerosol, and the filter is wrapped by a filter wrapper and by another wrapper that connects the filter and the wrapped rod with the aerosol-generating material to each other.

[0004] During the intended use of the aerosol-generating article, the aerosol-generating material is typically heated, but not burned. This heating can be performed, 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, which is operated, for example by ignition, in order to use the article. During the heating of the aerosol-generating material, the wrapping paper is also heated and thermally degraded. This can cause the wrapping paper to lose so much strength that it is torn during removal of the aerosol-generating article from the heating device. This requires additional cleaning work for the consumer and is therefore undesirable. In addition, for aerosol-generating articles with an integrated heat source, the wrapping paper can lose its strength during heating, causing the heat source to fall off and create a risk of fire.

[0005] In addition, it is desirable to prevent consumers from accidentally using the aerosol-generating article in the same manner as a cigarette and attempting to ignite the end of the aerosol-generating article, thereby initiating a combustion or smoldering process of the aerosol-generating material. Therefore, the packaging material of the aerosol-generating article needs to have flame retardant properties.

[0006] Attempts to make wrappers for such aerosol-generating articles heat-resistant or flame-retardant have been only partially successful.

[0007] For example, in WO 2015 / 082648, a wrapping paper is described which consists of relatively few pulp fibers and is coated with a composition of calcium carbonate and a binder such that at least 50% of the wrapping paper is formed by calcium carbonate. A disadvantage of this wrapping paper is that, due to the thick coating, it is relatively brittle and a large amount of dust is generated during the manufacture of an aerosol-generating article from the wrapping paper. Furthermore, due to the low pulp fiber content, the tensile strength is not particularly high.

[0008] In WO 2011 / 117750, a wrapping paper is described which consists 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. Disadvantages of this wrapping paper are the complex manufacturing process and the low biodegradability, since experience has shown that many aerosol-generating articles are simply disposed of in the environment after use.

[0009] It is therefore of interest to provide a wrapper which has sufficient tensile strength after heating, has a flame retardant effect and which is nonetheless biodegradable. Furthermore, the design of wrappers for aerosol-generating articles must take into account legal regulations, toxicology and the effect of the wrapper on the taste of the aerosol-generating article. Summary of the invention

[0010] It is an object of the present invention to provide a wrapper for an aerosol-generating article which is substantially heat-resistant or flame-retardant and has advantageous properties with respect to strength, processability, biodegradability and effect on taste.

[0011] In the context of the present invention, an aerosol-generating article is a rod-shaped article comprising an aerosol-generating material and a wrapper enclosing the aerosol-generating material, wherein during the intended use, the aerosol-generating material is only heated but not burned. If the aerosol-generating material is heated to a temperature of up to 400° C., in any case, heating will occur without burning for typical aerosol-generating materials (e.g., tobacco).

[0012] This object is achieved by a wrapper for an aerosol-generating article, an aerosol-generating article comprising such a wrapper, the use of such a wrapper for an aerosol-generating article and a method for producing a wrapper according to the invention. Further advantageous embodiments are provided.

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

[0014] According to the findings of the present inventors, in order to obtain a high initial strength of the wrapping paper, a high pulp fiber content is necessary. It is known that many char-forming agents that could potentially be used in paper damage the pulp fibers in the paper and therefore rapidly cause a significant loss of strength when heated. However, they protect the pulp fibers further within the paper structure from thermal degradation. Because paper is generally easy to burn, it is generally believed that char-forming agents need to be used in paper at very high concentrations to achieve an effective flame retardant effect. However, at such concentrations, the general assumption as well as the experiments of the present inventors show that the pulp fibers are so severely damaged and the strength is reduced so drastically that their use cannot be reasonably considered.

[0015] In contrast, the present inventors have found that for some char formers, there is actually a suitably narrow concentration range in which there is a good flame retardant effect and the strength reduction of the paper is not too great.

[0016] Only a combination of a high content of pulp fibers and a suitably selected concentration of a char-forming agent makes it possible to produce a wrapping paper which, due to its high initial strength and despite the loss of strength due to the char-forming agent, also has such a high tensile strength after heating that an aerosol-generating article produced therefrom can be removed from a heating device without any problems or the risk that a heat source integrated into the aerosol-generating article might fall off. Furthermore, the flame retardant effect is sufficient so that the aerosol-generating article cannot be smoked like a cigarette.

[0017] Additionally, the composition of the wrapper allows for excellent biodegradability and very good processability during the manufacture of the aerosol-generating article.

[0018] For its strength, the wrapping paper requires pulp fibers, wherein the pulp fibers account for at least 70% and at most 95% of the mass of the wrapping paper. In order to obtain an even better ratio between pulp fibers and char-forming agent, the proportion of pulp fibers may preferably be at least 75% and at most 90%, particularly preferably at least 80% and at most 90%, each relative to the mass of the wrapping paper.

[0019] The pulp fibers are preferably derived 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 in whole or in part from fibers derived from regenerated cellulose, such as Tencel. TM Fiber, Lyocell TM Fiber, Viscose or Modal TM fiber.

[0020] Preferably, the pulp fibers are formed of pulp fibers from coniferous trees in a proportion of at least 40% and at most 100% relative to the mass of the pulp fibers, since these pulp fibers provide high strength to the packaging paper.

[0021] The wrapping paper contains a char-forming agent, wherein the char-forming agent accounts for at least 5% and at most 20% of the mass of the wrapping paper. According to the findings of the inventors, the char-forming agent protects the pulp fibers located in the paper structure from strong oxidation, but it also damages the pulp fibers itself, so that the concentration of the char-forming agent must be within a narrow range and depends on the type of char-forming agent. When the concentration of the char-forming agent increases, the flame retardant effect is stronger, but due to the increased damage to the pulp fibers, the strength of the wrapping paper after heating decreases. Preferably, the proportion of the char-forming agent in the wrapping paper therefore accounts for at least 9% and at most 16% of the mass of the wrapping 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 preferably, the char-forming agent is guanidine phosphate, guanidine phosphate, phosphoric acid, phosphonate, melamine phosphate, dicyandiamide, boric acid or borax. These less preferred compounds are more difficult to process or are not completely unproblematic toxicologically. At the same time, sodium polyphosphate is a char-forming agent, but not a char-forming agent according to the invention.

[0023] The choice of the concentration of the char former is not free within the interval provided, but depends on the type of char former and must be chosen such that the reduction in the strength of the wrapping paper after heating is not too high.

[0024] For this purpose, the tensile strength of the wrapping paper in the longitudinal direction is determined as a characteristic of strength and is first determined under the conditions of ISO 187: 1990 and then after heating the wrapping paper. More precisely, the strength loss can be determined according to the following method.

[0025] First, paper samples of suitable geometry are adjusted according to ISO 187:1990, usually 15 mm wide strips, and tested in a tensile test according to ISO 1924-2:2008. The tensile strength depends on the sampling direction of the paper sample. In this context, tensile strength is always understood to be the tensile strength in the running direction of the packaging paper during paper production, the so-called longitudinal direction.

[0026] The initial tensile strength, denoted by R0, is determined according to the invention by conditioning the paper sample according to ISO 187:1990 without prior heat loading and testing according to ISO 1924-2:2008. T It is measured by exposing the sample to a temperature of 230°C for a period of one minute in air, where the air can reach substantially all sides of the paper sample and there is a low air flow. The paper sample is then conditioned according to ISO 187:1990 and the tensile strength is also measured according to ISO 1924-2:2008. The quotient r = R T / R0 describes the proportion of the tensile strength remaining after thermal loading of the wrapping paper and thus characterizes the thermal resistance of the wrapping paper. High values ​​of the quotient r describe a high thermal resistance. According to the invention, the concentration of the charring agent in the wrapping paper should be selected so that the tensile strength R after thermal loading (230° C., 1 minute) is T The quotient r with the initial tensile strength R0 is at least 0.20 and at most 0.90 and 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] This quotient can be affected by the amount of pulp fibers and the type and concentration of the char-forming agent, wherein more pulp fibers result in a higher initial tensile strength R0, and an increased concentration of the char-forming agent generally results in a higher tensile strength R0 after thermal loading. T Depending on the type of application of the aerosol generating product, the carbonizing agent has a significant effect on the tensile strength R T The negative effects of charring have to be balanced against a better flame retardant effect with increasing concentration. It has been found that within the interval of charring agent concentrations according to the invention and preferred, a very good compromise can be found for aerosol generating articles.

[0028] Preferably, after thermal loading, the tensile strength R T should not fall below a certain value so that the aerosol-generating article can be handled without trouble during and after use. Preferably, after thermal loading, the tensile strength R of the wrapper in the longitudinal direction is T It 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 findings of the present inventors, it is important to know how the char-forming agent is distributed over the thickness of the wrapping paper. Generally, if the char-forming agent is substantially evenly distributed in the wrapping paper, a good flame retardant effect can actually be obtained. However, in a preferred embodiment, the wrapping paper is designed so that the side of the wrapping paper facing the aerosol generating material contains a higher proportion of char-forming agent than the other side of the wrapping paper. The side facing the aerosol generating material is usually exposed to a higher heat load. Therefore, a higher content of char-forming agent on this side of the wrapping paper can make a particularly good contribution to the flame retardant effect. In this way, the proportion of char-forming agent in the wrapping paper can be reduced without losing the flame retardant effect, and therefore for the same basis weight, the proportion of pulp fibers in the wrapping paper can be increased, thereby increasing the strength of the wrapping paper as a whole. Alternatively, under this preferred distribution of the char-forming agent in the wrapping paper, the basis weight can also be reduced without losing the flame retardant effect, which reduces the material requirements.

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

[0031] Preferably, the char-forming agent is substantially uniformly distributed over at least 70% of the surface area of ​​the wrapper, particularly preferably over at least 95% of the surface area, wherein variations in the proportion of the char-forming agent within these surface areas are caused only by manufacturing and are not intended.

[0032] A disadvantage of a char-forming agent may be that it discolors the wrapping paper so that it darkens under thermal stress. This disadvantage can be overcome by combining the wrapping paper according to the invention with a further paper layer, for example by gluing, so that the wrapping paper according to the invention faces the aerosol-generating material and the further paper layer is on the side facing away from the aerosol-generating material. Under thermal stress, the further paper layer covers the wrapping paper so that the color visible from the outside does not change or only changes insignificantly.

[0033] Preferably, the wrapping paper is thus combined with a paper layer. Particularly preferably, the paper layer contains pulp fibers and calcium carbonate particles, wherein the calcium carbonate particles account for at least 15% and at most 40% of the mass of the paper layer. The calcium carbonate particles provide the paper layer with a white color and a high opacity, so that discoloration of the wrapping paper according to the invention is not visible or is only slightly visible. It should be noted that the wrapping paper with the other paper layer as a whole can also be described as a "two-layer wrapping paper", but this designation is avoided here. On the contrary, in the language of the present disclosure, such a two-layer structure is referred to as a "wrapping paper with another paper layer", because only the part of the two-layer structure referred to as "wrapping paper" needs to meet the above requirements regarding the quotient of pulp fibers, char-forming agent and tensile strength.

[0034] In addition to pulp fibers and char-forming agents, the wrapping paper according to the present invention may also contain other components. This includes, for example, filler materials, sizing agents, wet strength agents, additives, processing aids, wetting agents and flavoring agents. The skilled person can select these components based on experience. In particular, wet strength agents can contribute to the application of aerosol-generating articles, because the aerosols formed during the use of aerosol-generating articles have a high moisture content. The wrapping paper can absorb water from the aerosol, so its strength is reduced. This can be prevented by using a wet strength agent.

[0035] Filling materials in the wrapping paper can help reduce discoloration of the wrapping paper. However, filling materials also reduce the tensile strength of the wrapping paper, so their proportion should not be too high. Preferably, the proportion of filling materials in the wrapping paper is therefore 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%, each relative to the mass of the wrapping paper.

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

[0037] In a preferred embodiment, the wrapper additionally contains starch or a starch derivative, or is coated with starch or a starch derivative. In this preferred embodiment, the proportion of starch or starch derivatives is at least 2% and at most 10% of the mass of the wrapper. This preferred embodiment provides resistance to oil penetration as an additional advantage. The aerosol-generating material may contain oils, such as flavorings, which penetrate the wrapper and cause stains during storage or use of the aerosol-generating article. The 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 wrapping paper can vary, wherein a higher basis weight generally also means a higher tensile strength. However, with a higher basis weight, the wrapping paper becomes harder and more difficult to process, and the material requirement increases. Preferably, the basis weight of the wrapping paper according to the invention is therefore at least 15 g / m2 and at most 80 g / m2, particularly preferably at least 20 g / m2 and at most 60 g / m2. The basis weight of the wrapping paper can be determined according to ISO 536:2019.

[0039] The thickness of the wrapping paper primarily influences the bending stiffness and the heat transfer within the wrapping paper. A high bending stiffness is advantageous because an aerosol-generating article made from the wrapping paper deforms less, but on the other hand a high bending stiffness may cause problems due to restoring forces when an aerosol-generating material is to be wrapped with the wrapping paper. A high thickness slows down the heat transfer through the wrapping paper and is also advantageous for this purpose. Preferably, the wrapping paper according to the invention has a thickness of 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 on a single layer according to ISO 534:2011.

[0040] The initial tensile strength R0 of the wrapping paper measured in the longitudinal 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. High tensile strengths can be achieved by a high proportion of pulp fibers. However, this also means higher material requirements, so that particularly high tensile strengths cannot be felt to be desirable. The preferred interval allows a particularly advantageous combination of trouble-free processability and material requirements. The tensile strength can be determined according to ISO 1924-2:2008.

[0041] The aerosol generating material usually contains a humectant so that during heating, the generated aerosol has a relatively high moisture content. This moisture can reduce the strength of the wrapping paper, so it is advantageous if the wrapping paper also has a suitable wet strength. Therefore, the wet tensile strength in the longitudinal direction 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. The wet tensile strength in the longitudinal direction can be determined according to ISO 12625-5:2016.

[0042] The air permeability of the wrapping paper may be low. Low air permeability can usually be obtained by more intensive refining of the pulp fibers. This also contributes to the increase in strength, so that preferably the air permeability is at least 0 cm3 / (cm2·min·kPa) and at most 50 cm3 / (cm2·min·kPa), particularly preferably at least 0 cm3 / (cm2·min·kPa) and at most 20 cm3 / (cm2·min·kPa). The air permeability can be measured according to ISO 2965:2019.

[0043] Optical properties may be important if the wrapper according to the invention is visible from the outside on the aerosol-generating article. Typically, high opacity and high brightness are desired. The type and amount of filler material in the wrapper can significantly influence both properties. 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] An aerosol-generating article may be manufactured from the wrapper 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 according to one of the preceding embodiments, wherein the wrapper packages the aerosol-generating material.

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

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

[0047] The packaging paper according to the invention can be manufactured according to the following method according to the invention, comprising steps A to G.

[0048] A – Suspending pulp fibers in an aqueous suspension,

[0049] B – Refining of suspended pulp fibers in a refining unit,

[0050] C—applying said suspension to a running web,

[0051] D – Forming a fiber web by dewatering the suspension,

[0052] E – pressed fiber web,

[0053] F – Drying fiber web,

[0054] G – Roll up the wrapping paper,

[0055] Between steps F and G, at least one composition comprising a char-forming agent is applied to the fiber web and the fiber web is dried to form a wrapper, and wherein the wrapper from step G comprises pulp fibers and a char-forming agent, and the pulp fibers account for at least 70% and at most 95% of the mass of the wrapper, and the char-forming agent accounts for at least 5% and at most 20% of the mass of the wrapper, and wherein the char-forming agent is contained in the wrapper in a concentration such that the tensile strength R0 measured under the conditions of ISO 187:1990 according to ISO 1924-2:2008 is less than the tensile strength R0 measured under the conditions of ISO 187:1990 according to ISO 1924-2:2008 after the wrapper has been exposed to a temperature of 230°C for a period of 1 minute. T The quotient r = R T / R0 is at least 0.20 and at most 0.90.

[0056] Preferably, the step of applying the composition comprising the char-forming agent to the fiber web is performed by one or a combination of two or more of the following steps:

[0057] F.1 applying a composition comprising a char-forming agent to a fiber web in a size press of a paper machine,

[0058] F.2 applying a composition comprising a char-forming agent to a fiber web on one side in a film press or in a coating unit of a paper machine, and

[0059] F.3 A composition comprising a char-forming agent is applied to the fiber web on one side by printing, in particular rotogravure printing or spraying.

[0060] In this regard, step F.1 is carried out in a size press, so that the fiber web is impregnated with a composition comprising a char-forming agent. This variant offers advantages that can be easily realized. It usually results in a substantially uniform distribution of the char-forming agent over the thickness of the wrapping paper, so that relatively more char-forming agent is required to obtain the desired effect. However, it is also possible in fact to adjust the settings of the size press in this step so that the char-forming agent is unevenly distributed over the thickness of the fiber web and thus unevenly distributed over the thickness of the wrapping paper.

[0061] According to step F.2, the composition containing the char-forming agent is applied to one side of the fiber web in a film press or in a coating unit. This results in an uneven distribution of the char-forming agent over the thickness of the packaging paper, and a high flame retardant effect can be achieved with a smaller proportion of the char-forming agent in the packaging paper.

[0062] According to step F.3, a composition comprising a char-forming agent is applied to one side of the web by printing or spraying, wherein in a particularly preferred embodiment, the composition is printed on one side of the web by a rotary gravure printing unit. In this regard, the web is preferably dried, rolled up and unrolled before step F.3. In the rolled-up state, the web can then be transported to another device, where the application of the composition can be carried out by printing or spraying. Although steps F.1 and F.2 can usually be carried out on the same paper machine on which the packaging paper is manufactured, the application according to step F.3 is usually carried out in a separate device.

[0063] In a highly particularly preferred embodiment, steps F.1 and F.3 are combined so that first in step F.1 the fiber web is impregnated with a composition comprising a char former in a size press, and in step F.3 a further composition comprising a char former is printed on one side of the fiber web in a rotogravure printing unit. In this highly particularly preferred embodiment, the char former is both distributed in the packaging paper and present in a higher concentration on one side of the packaging paper, so that the flame retardant effect can be significantly further increased.

[0064] In a further highly preferred embodiment, steps F.1 and F.2 are combined, wherein step F.1 is carried out in a size press and step F.2 is carried out in a coating unit. In this highly preferred embodiment, the packaging paper can be produced particularly efficiently, since, for example, all application devices can be integrated into one paper machine.

[0065] Independently of using one or more of steps F.1, F.2 or F.3, the composition comprising the char-forming agent is preferably applied to at least 70% of the surface area of ​​the wrapper, particularly preferably to at least 95% of the surface area of ​​the wrapper.

[0066] The composition used in step F.1, F.2 or F.3 comprises a char-forming agent and a solvent, wherein the solvent is preferably water. The amount of char-forming agent in the composition may vary and depends on the type of application process, the amount of char-forming agent to be applied in the wrapping paper and the amount required. A person skilled in the art will be able to determine a suitable composition taking these factors into account and will be able to design the application process accordingly.

[0067] In a highly particularly preferred embodiment, one of steps F.1 and F.2 is carried out, and then the fiber web is dried, rolled up and unfolded again, and then step F.3 is carried out, wherein the fiber web in the dry, rolled-up state before step F.3 contains a carbon-forming agent, and the amount of carbon-forming agent is preferably at least 5% and at most 10% of the mass of the fiber web in the dry and rolled-up state.

[0068] If steps F.1 , F.2 and / or F.3 are combined in any form, the compositions comprising the char-forming agent applied in steps F.1 , F.2 and / or F.3 may be different.

[0069] In the wrapper after step G, pulp fibers account for at least 70% and at most 95% of the mass of the wrapper. In order to obtain an even better ratio between pulp fibers and char-forming agent, the proportion of pulp fibers may preferably be at least 75% and at most 90%, and particularly preferably at least 80% and at most 90%, each relative to the mass of the wrapper after step G.

[0070] The pulp fibers in step A are preferably derived 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 in whole or in part from fibers produced from regenerated cellulose, such as Tencel. TM Fiber, Lyocell TM Fiber, Viscose or Modal TM fiber.

[0071] Preferably, the pulp fibers in step A are formed of pulp fibers from coniferous trees in a proportion of at least 40% and at most 100% relative to the mass of the pulp fibers, since these pulp fibers provide high initial strength to the packaging paper in step G.

[0072] The wrapper after step G contains the char-forming agent, wherein the char-forming agent accounts for at least 5% and at most 20% of the mass of the wrapper. Preferably, after step G, the proportion of the char-forming agent in the wrapper is at least 9% and at most 16% of the mass of the wrapper.

[0073] Preferably, the char-forming agent is ammonium phosphate, particularly preferably monoammonium phosphate, diammonium phosphate, triammonium phosphate or ammonium polyphosphate or a mixture thereof. Less preferably, the char-forming agent is guanidine phosphate, guanidine phosphate, phosphoric acid, phosphonate, melamine phosphate, dicyandiamide, boric acid or borax. These less preferred compounds are more difficult to process or are not completely toxicologically unproblematic. At the same time, sodium polyphosphate is a char-forming agent, but not according to the invention.

[0074] In a preferred embodiment, after step G, the wrapper is a wrapper according to one of the preceding embodiments. DETAILED DESCRIPTION

[0075] Some preferred embodiments of the wrapping paper according to the invention will now be described.

[0076] The packaging paper P1 according to the invention is manufactured on a Fourdrinier paper machine. To this end, pulp fibers are suspended in water (step A) and refined in a refining unit (step B). The suspension is then applied to a running web (step C) and dewatered there to form a fiber web (step D). The fiber web is squeezed (step E) for further dewatering and dried by contact with a heated drying cylinder (step F). In the size press of the paper machine, the fiber web is impregnated over the entire surface of both sides with a composition comprising water and monoammonium phosphate (step F.1) and then dried by contact with a heated drying cylinder. Finally, the fiber web is rolled up (step G) and the packaging paper P1 according to the invention is obtained.

[0077] The amount of pulp fibers is selected such that about 87% of the mass contained in the wrapper P1 is pulp fibers. The composition in step F.1 comprises water and monoammonium phosphate and is selected together with the settings of the size press such that the amount of monoammonium phosphate in the wrapper after step G is about 7%. The distribution of the monoammonium phosphate in the wrapper P1 through the thickness can be considered to be substantially uniform.

[0078] The wrapping paper P2 according to the invention is manufactured from the wrapping paper P1 according to the invention by unwinding a reel of the wrapping paper P1 and printing a composition comprising water and monoammonium phosphate in a rotogravure printing unit over the entire surface of one side of the wrapping paper (step F.3). The wrapping paper is then dried by hot air drying and rolled up again (step G). The composition in step F.3 is selected together with the settings of the rotogravure printing unit and in particular with the geometry of the printing cylinder so that in the finished wrapping paper P2, a total of 12.5% ​​of the mass of the wrapping paper is formed by monoammonium phosphate. In this way, an inhomogeneous distribution of the monoammonium phosphate in the wrapping paper is obtained, so that the content of monoammonium phosphate is higher on the printed side than on the other side.

[0079] In the wrapping paper P2, 82% by mass was formed from pulp fibers.

[0080] A packaging paper Z1 not according to the invention comprising 70% pulp fibers and 29% precipitated calcium carbonate but without a carbon-forming agent was used as a comparative example.

[0081] In addition, the carbon-forming agent containing 90% pulp fiber and 10% sodium polyphosphate (NaPO3) n A wrapping paper Z2 which is not according to the invention was used as a comparative example.

[0082] To obtain a further wrapper P3, a wrapper Z1 not according to the invention was glued to a wrapper P2 according to the invention to form a two-layer structure in such a way that the side of the wrapper P2 with the higher content of monoammonium phosphate faced away from the wrapper Z1.

[0083] The data for the packaging papers P1 and P2 according to the invention, the two-layer structure P3 and the comparative examples Z1 and Z2 not according to the invention were determined according to conventional standards.

[0084] To determine the tensile strength R after thermal loading T The packaging papers P1, P2, P3 and Z1, Z2 were stored for 1 minute in a drying cabinet 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.

[0085] From the initial tensile strength R0 and the tensile strength after heat load R T Determine the quotient r = R T / R0 is used to characterize heat resistance.

[0086] All data for packaging papers P1, P2, P3 and Z1, Z2 can be found in Table 1.

[0087] Table 1

[0088] P1 P2 P3 Z1 Z2 Basis Weight g / m2 28.8 31.9 72.2 29 30.3 thickness μm 46.4 46.4 79.2 45.3 47.3 <![CDATA[Tensile strength R0]]> N / 15mm 30.4 36.0 65.7 15.2 32.7 <![CDATA[Tensile strength R T > N / 15mm 16.7 12.1 27.2 14.3 6.3 <![CDATA[r=R T / R0]]> 0.55 0.34 0.41 0.94 0.19 Wet tensile strength N / 15mm 3.0 3.0 10.1 2.5 3.1 Breathability cm3 / (cm2·min·kPa) <20 <20 <20 60 <20 Opacity ％ 44.8 41.8 41.2 brightness ％ 87.4 88.6 88.6

[0089] Table 1 shows that for the wrappers P1 and P2 according to the invention, and for the two-layer structure P3 comprising the wrapper P2 according to the invention, the heat load reduces the tensile strength to 34% to 55%. For the comparative example Z1 not according to the invention, which does not contain a char-forming agent, the tensile strength is hardly reduced by the heat load and remains about 94% of the initial tensile strength. For the comparative example Z2 not according to the invention, which contains sodium polyphosphate as a char-forming agent, the tensile strength after the heat load is only about 19% of the initial tensile strength, and the absolute value of 6.3 N / 15 mm is too low to allow the aerosol-generating article produced therefrom to be removed from the heating device without problems after use.

[0090] The wrappers P1 and P2 according to the invention and the double-layer structure P3 all show an acceptable reduction in tensile strength. However, it is worth noting that the higher the content of monoammonium phosphate in the wrapper P2, the greater the damage to the fibers and the greater the reduction in tensile strength after thermal loading compared to the wrappers P1 and P2 according to the invention.

[0091] In addition to the fact that the reduction in tensile strength is not too strong, the flame retardant effect is also important. In order to test the flame retardant effect, aerosol-generating articles for heating devices were manufactured from wrapping papers P1 / P2 according to the invention, the double-layer structure P3 and the comparative examples Z1 and Z2 not according to the invention. The manufacture of aerosol-generating articles was without any problems for all wrapping papers. When trying to ignite an aerosol-generating article such as a cigarette with a lighter, it was immediately clear that the comparative example Z1 not according to the invention had no flame retardant effect. The aerosol-generating articles thus manufactured can be ignited without problems. Despite the longer action of the flame of the lighter, the aerosol-generating articles with the wrapping papers P1 / P2 according to the invention, the double-layer structure P3 and the comparative example Z2 not according to the invention cannot be ignited so that combustion or a stable smoldering process can be initiated. These aerosol-generating articles cannot be smoked according to standardized methods either. With regard to the flame retardant effect, the wrapping paper P2 according to the invention proved to be slightly better than P1, which shows that the uneven distribution of the charring agent over the thickness of the wrapping paper can help to enhance the flame retardant effect.

[0092] The two-layer structure P3 is a laminate of a wrapper P2 according to the invention and a comparative example Z1 not according to the invention, and after use of an aerosol-generating article made therefrom, shows significantly less discoloration than aerosol-generating articles having P1 and P2. Thus, the wrapper Z1 fulfills its function of concealing the discoloration of the wrapper P2.

[0093] No effect on the taste of the aerosol generating preparation was found.

[0094] The wrapping paper according to the invention is therefore very well suited for use in aerosol generating articles and has good biodegradability, a better combination of strength and flame retardant effect after heating than comparable wrapping papers of the prior art.

Claims

1. An aerosol-generating article comprising a wrapper and an aerosol-generating material, wherein the aerosol-generating article is heated but not burned during intended use, wherein the wrapper encloses the aerosol-generating material, wherein the wrapper comprises pulp fibers and a char-forming agent, wherein the pulp fibers account for at least 70% and at most 95% of the mass of the wrapper, and the char-forming agent is contained in a concentration of at least 5% and at most 20% relative to the mass of the wrapper, and is present in the wrapper in such a concentration that the tensile strength R0 measured under the conditions of ISO 187:1990 according to ISO 1924-2:2008 is equal to the tensile strength R0 measured under the conditions of ISO 187:1990 according to ISO 1924-2:2008 after the wrapper has been exposed to a temperature of 230°C for a period of 1 minute. T The quotient r = R T / R0 is at least 0.20 and at most 0.90, wherein the char-forming agent is ammonium phosphate, or wherein the char-forming agent is at least partially formed from guanidine phosphate, guanidine phosphate, phosphoric acid, phosphonate, melamine phosphate, dicyandiamide, boric acid or borax.

2. An aerosol-generating article according to claim 1, wherein the proportion of pulp fibres in the wrapper is at least 75% and at most 90% relative to the mass of the wrapper.

3. An aerosol-generating article according to claim 2, wherein the proportion of pulp fibres in the wrapper is at least 80% and at most 90% relative to the mass of the wrapper.

4. An aerosol-generating article according to claim 1 or 2, wherein the pulp fibers are derived in whole or in part from one or more plants selected from coniferous trees, deciduous trees, flax, hemp, jute, ramie, abaca, sisal, kenaf and cotton.

5. An aerosol-generating article according to claim 4, wherein the conifer is one or more of spruce, pine and fir.

6. An aerosol-generating article according to claim 4, wherein the deciduous tree is one or more of beech, birch and eucalyptus.

7. An aerosol-generating article according to claim 1 or 2, wherein the pulp fibers are formed in whole or in part from fibers derived from regenerated cellulose.

8. An aerosol-generating article according to claim 7, wherein the fibers are made of Tencel TM Fiber, Lyocell TM Fiber, Viscose or Modal TM Fiber formation.

9. An aerosol-generating article according to claim 1 or 2, wherein the pulp fibres originate from coniferous trees in a proportion of at least 40% and at most 100% relative to the mass of the pulp fibres.

10. An aerosol-generating article according to claim 1 or 2, wherein the proportion of the char-forming agent in the wrapper is at least 9% and at most 16% by mass of the wrapper.

11. An aerosol-generating article according to claim 1 or 2, wherein the char-forming agent is monoammonium phosphate, diammonium phosphate, triammonium phosphate, ammonium polyphosphate or a mixture thereof.

12. An aerosol-generating article according to claim 1 or 2, wherein after the wrapper has been exposed to a temperature of 230°C for a period of 1 minute, the tensile strength R T It is at least 8 N / 15 mm and at most 50 N / 15 mm.

13. An aerosol-generating article according to claim 12, wherein after the wrapper has been exposed to a temperature of 230°C for a period of 1 minute, the tensile strength R T At least 10 N / 15 mm and at most 40 N / 15 mm.

14. An aerosol-generating article according to claim 1 or 2, wherein the side of the wrapper that faces the aerosol-generating material during intended use comprises a higher proportion of char-forming agent than the other side of the wrapper.

15. An aerosol-generating article according to claim 1 or 2, wherein the char-forming agent is at least uniformly distributed over at least 70% of the surface area of ​​the wrapper.

16. An aerosol-generating article according to claim 15, wherein the char-forming agent is at least uniformly distributed over at least 90% of the surface area of ​​the wrapper.

17. An aerosol-generating article according to claim 1 or 2, wherein the wrapper is combined with another paper layer so that the wrapper faces the aerosol-generating material during intended use and the other paper layer is arranged on the side facing away from the aerosol-generating material.

18. An aerosol-generating article according to claim 17, wherein the further paper layer comprises pulp fibres and calcium carbonate particles, wherein the calcium carbonate particles comprise at least 15% and at most 40% of the mass of the further paper layer.

19. An aerosol-generating article according to claim 1 or 2, wherein the wrapper further comprises at least one additional component selected from the group consisting of filler materials, sizing agents, wet strength agents, humectants and flavouring agents.

20. An aerosol-generating article according to claim 1 or 2, wherein the wrapper further comprises at least one additional component selected from additives.

21. An aerosol-generating article according to claim 1 or 2, wherein the wrapper further comprises at least one additional component selected from processing aids.

22. An aerosol-generating article according to claim 19, wherein the proportion of filler material relative to the mass of the wrapper is at least 0% and at most 20%.

23. An aerosol-generating article according to claim 19, wherein the proportion of filler material relative to the mass of the wrapper is at least 0% and at most 10%.

24. An aerosol-generating article according to claim 19, wherein the proportion of filler material relative to the mass of the wrapper is at least 0% and at most 5%.

25. An aerosol-generating article according to claim 19, wherein the filler material is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talc, and mixtures thereof.

26. An aerosol-generating article according to claim 1 or 2, wherein the wrapper contains starch or a starch derivative, or is coated with starch or a starch derivative.

27. An aerosol-generating article according to claim 26, wherein the proportion of starch or starch derivative is at least 2% and at most 10% by mass of the wrapper.

28. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a KIT level of at least 4 and at most 8 as measured according to TAPP T559cm-12.

29. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a basis weight of at least 15 g / m2 and at most 80 g / m2.

30. An aerosol-generating article according to claim 29, wherein the wrapper has a basis weight of at least 20 g / m2 and at most 60 g / m2.

31. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a thickness of at least 25 μm and at most 100 μm.

32. An aerosol-generating article according to claim 31 , wherein the wrapper has a thickness of at least 40 μm and at most 80 μm.

33. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a tensile strength R0 before heat loading measured in the longitudinal direction of at least 10 N / 15 mm and at most 100 N / 15 mm.

34. An aerosol-generating article according to claim 33, wherein the wrapper has a tensile strength R0 before heat loading measured in the longitudinal direction of at least 20 N / 15 mm and at most 80 N / 15 mm.

35. An aerosol-generating article according to claim 1 or 2, wherein its wet tensile strength in the longitudinal direction according to ISO 12625-5:2016 is at least 1 N / 15 mm and at most 10 N / 15 mm.

36. An aerosol-generating article according to claim 35, wherein its wet tensile strength in the longitudinal direction according to ISO 12625-5:2016 is at least 2 N / 15 mm and at most 8 N / 15 mm.

37. An aerosol-generating article according to claim 1 or 2, wherein the air permeability of the wrapper is at least 0 cm3 / (cm2·min·kPa) and at most 50 cm3 / (cm2·min·kPa).

38. An aerosol-generating article according to claim 37, wherein the air permeability of the wrapper is at least 0 cm3 / (cm2·min·kPa) and at most 20 cm3 / (cm2·min·kPa).

39. An aerosol-generating article according to claim 1 or 2, wherein the opacity of the wrapper is at least 40% and at most 80%, and / or the brightness of the wrapper is at least 80% and at most 95%.

40. An aerosol-generating article according to claim 1 or 2, wherein the opacity of the wrapper is at least 45% and at most 80%, and / or the brightness of the wrapper is at least 83% and at most 90%.

41. An aerosol-generating article according to claim 1 or 2, wherein the proportion of the char-forming agent on one side of the wrapper is higher than that on the other side, and the side with the higher proportion of the char-forming agent faces the aerosol-generating material.