Wrapping paper with improved flame retardancy

Abstract

The present invention relates to a wrapping paper suitable for use in an aerosol generating article and comprising pulp fibres and one or more polyphosphates, wherein the pulp fibres constitute at least 55% and at most 95% by mass of the wrapping paper and the polyphosphates are contained together in a concentration of at least 5% and at most 30% relative to the mass of the wrapping paper. In this regard, the polyphosphate is a polyphosphate having the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ] wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH4 + ).

Description

Field of the Invention

[0001] The present invention relates to a wrapping paper for an aerosol-generating article, which has a relatively high heat resistance and, therefore, after use of the article, still has sufficient mechanical strength to ensure problem-free handling of the article and, in addition, has a flame retardant effect, so that an aerosol-generating article made from the wrapping paper does not smoke like a smoking article. The wrapping paper according to the invention has improved flame retardancy compared to known heat-resistant wrapping papers. This is achieved by a high content of specific polyphosphates in the wrapping paper.

[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, which is biodegradable, and which functions as a particularly effective flame retardant. 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 aerosol-generating articles which is substantially heat-resistant and strongly flame-retardant and has advantageous properties with regard 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 materials).

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

[0013] The inventors have found that this object can be achieved by a wrapping paper which is suitable for use in an aerosol generating article and comprises pulp fibers and one or more polyphosphates, wherein the pulp fibers account for at least 55% and at most 95% of the mass of the wrapping paper, and the polyphosphates are contained together in a concentration of at least 5% and at most 30% relative to the mass of the wrapping paper.

[0014] According to the findings of the inventors, in order to obtain a high strength of the wrapping paper, a high pulp fiber content is necessary. Additives such as polyphosphates according to the invention can prevent the formation of hydrogen bonds between pulp fibers, thereby reducing the strength of the wrapping paper. However, in order to obtain a good flame retardant effect, high concentrations of polyphosphates are sometimes required, so that the proportion of pulp fibers in the wrapping paper must be high. Therefore, only small amounts of additional components can be included in the wrapping paper; in particular, components that further reduce the strength are not desired.

[0015] Only a combination of a high content of pulp fibers and a properly selected concentration of polyphosphate makes it possible to produce a wrapping paper which, due to its high initial strength, 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 so good that the aerosol-generating article cannot be smoked like a cigarette.

[0016] The composition of the wrapper additionally allows for excellent biodegradability and very good processability during the manufacture of the aerosol-generating article.

[0017] For its strength, the wrapping paper requires pulp fibers, wherein the pulp fibers account for at least 55% and at most 95% of the mass of the wrapping paper. In order to obtain an even better ratio between pulp fibers and polyphosphate, the proportion of pulp fibers may preferably be at least 70% and at most 90%, more particularly preferably at least 75% and at most 90%, each relative to the mass of the wrapping paper.

[0018] The pulp fibers are preferably derived from one or more plants selected from the group consisting of conifers, deciduous trees, annual plants, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, bamboo, 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.

[0019] Preferably, the pulp fibers are formed from pulp fibers from coniferous trees in a proportion of at least 25% and at most 100% relative to the mass of the pulp fibers, since these pulp fibers provide high strength to the packaging paper.

[0020] The wrapping paper contains one or more polyphosphates, wherein the polyphosphates together account for at least 5% and at most 30% of the mass of the wrapping paper. According to the findings of the inventors, the polyphosphates protect the pulp fibers within the paper structure from strong oxidation. In addition, according to the findings of the inventors, the polyphosphates are strongly hygroscopic and therefore allow water to be stored in the paper. When the paper is heated, water is first removed from the polyphosphates, thereby limiting the temperature of the pulp fibers. Since the heating process during normal use of the aerosol generating article is limited in time and does not exceed a few minutes, in particular when trying to ignite the aerosol generating article, the heating process only lasts for a few seconds, the water stored in the polyphosphates makes a substantial contribution to providing a flame retardant effect. This leads to advantages over the wrapping papers known in the prior art.

[0021] The flame retardant effect will increase with increasing polyphosphate concentration, but the strength of the wrapper will decrease, especially after heating. Preferably, the proportion of polyphosphate combined in the wrapper is therefore at least 8% and at most 27% by mass of the wrapper, in particular at least 9% and at most 25% by mass of the wrapper.

[0022] In the context of the present invention, a polyphosphate is a salt having the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ] wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH4 + ).

[0023] Thus, this definition also includes compounds known as oligophosphates, which have the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ], and wherein the value of n is generally at least 2 and at most 10. In addition, the definition also includes mixtures of polyphosphates with different n values ​​or with different monovalent metals M or ammonium in the intervals or preferred intervals according to the invention, or mixtures of linear and cyclic polyphosphates. It is contemplated and also within the scope of the present invention that in the case of polyphosphates with higher n values, for example greater than 10, there are mixtures of polyphosphates with different n values. In this context, mixtures of polyphosphates with different n values ​​fall within the definition, provided that the average value of n is within the intervals or preferred intervals according to the invention, wherein n is not necessarily an integer.

[0024] Polyphosphates having an n value of at least 3 and at most 80 are preferred, and n values ​​of at least 10 and at most 35 are particularly preferred.

[0025] Preferably, and independently of the choice of n, M is a monovalent metal selected from lithium, sodium and potassium or ammonium, and particularly preferably, the monovalent metal is sodium.

[0026] More particularly preferably, the polyphosphate has an n value of at least 15 and at most 30, and the monovalent metal M is sodium. In particular, the polyphosphate comprises sodium hexametaphosphate.

[0027] According to the discovery of the inventors, it is important to know how polyphosphate is distributed on the thickness of the wrapping paper. Generally, if polyphosphate 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 or away from the aerosol generating material contains a higher proportion of polyphosphate than the other side of the wrapping paper. Preferably, the polyphosphate content is higher on the side of the wrapping paper where the aerosol generating article manufactured by it is heated, because this side is exposed to a higher heat load. Therefore, a higher polyphosphate content on this side of the wrapping paper can make a particularly good contribution to the flame retardant effect. In this way, the proportion of polyphosphate 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 polyphosphate in the wrapping paper, the basis weight can be reduced without losing the flame retardant effect, which reduces the material requirements.

[0028] The distribution of polyphosphate in the wrapper can be influenced by the manufacturing process, as will be explained further below.

[0029] Preferably, the polyphosphate 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 polyphosphate within these areas are caused only by production and are not intentional. In this context, such uniform distribution refers to the distribution relative to the surface, not to the distribution in the thickness direction.

[0030] For various reasons, it is preferred if the wrapper is connected to another material layer, in particular a paper layer. The connection is preferably formed by an adhesive connection, but any type of connection is possible; in particular, it is sufficient to place the wrapper and the other layer on top of each other and roll them together, so that during the manufacture of the aerosol-generating article, the wrapper and the other layer will be on top of each other and together enclose the aerosol-generating material. The additional layer may be applied to either of the two sides of the wrapper, so that it can face or face away from the aerosol-generating material on the aerosol-generating article manufactured therefrom according to the desired effect.

[0031] The wrapper is connected to one or more paper layers or is also connected to a regenerated cellulose (e.g. cellulose hydrate) ), the above requirements regarding the proportions of pulp fibers and polyphosphates and all other properties mentioned below apply only to the wrapping paper itself and, unless expressly mentioned, not to other layers connected to it.

[0032] One reason for connecting the wrapping paper to another layer can be, for example, that polyphosphates cause the wrapping paper to change to a dark color under thermal load. This disadvantage can be overcome by connecting the wrapping paper according to the invention to another material layer so that the wrapping paper according to the invention faces the aerosol generating material and the other paper layer is on the side facing away from the aerosol generating material. Under thermal load, the other layer covers the wrapping paper so that the color visible from the outside does not change or only changes insignificantly.

[0033] In this particularly preferred embodiment, the wrapping paper is thus connected to a further paper layer, wherein the further paper layer comprises pulp fibers and white filler particles, and the white filler particles account for at least 15% and at most 45% of the mass of the paper layer. Particularly preferably, the white filler particles are calcium carbonate particles. The white filler particles provide the paper layer with a white color and a high opacity, so that discoloration of the wrapping paper according to the invention located thereunder is not visible or only slightly visible.

[0034] Another reason to connect the wrapper to another material layer is, for example, to prevent stains from forming on the wrapper. The aerosol generating material may contain oils, such as flavorings, which penetrate the wrapper during storage or when heated and cause stains. This problem can be overcome by connecting the wrapper to another material layer.

[0035] In this particularly preferred embodiment, the wrapping paper is thus connected to a further paper layer, wherein the further paper layer has a thickness of at least 5 cm measured according to ISO 2965:2019. 3 / (cm 2 ·min·kPa) and up to 30000cm 3 / (cm 2 ·min·kPa), and the basis weight of the additional paper layer is at least 10g / m 2 And up to 30g / m 2 The additional air permeability of the paper layer is a result of the porous structure, which hinders the transfer of oil or other components through the paper layer.

[0036] Another reason to connect the wrapper to a further material layer is, for example, to increase the stiffness of the wrapper. There are often cavities inside aerosol-generating articles so that a consumer can accidentally compress the aerosol-generating article during handling of the aerosol-generating article, thereby deforming it so that, for example, it can no longer be inserted into a heating device. A wrapper connected to another layer with high stiffness can prevent this.

[0037] In this particularly preferred embodiment, the wrapping paper is thus connected to a further paper layer, wherein the further paper layer has a thickness of at least 30 g / m 2 And up to 100g / m 2 The high basis weight is preferred as this also results in high bending stiffness.

[0038] Although paper layers are generally preferred for the additional layer provided on the packaging paper for the above reasons or for other reasons due to their good biodegradability, less preferably, the additional layer can also be made of aluminum foil, plastic foil or of regenerated cellulose such as cellulose hydrate. The produced foil is formed.

[0039] The wrapping paper according to the invention or the additional paper layer connected thereto for the aforementioned reasons or for other reasons may contain additional components. This includes, for example, filling 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 facilitate the use of aerosol-generating articles, because the aerosol formed during the use of aerosol-generating articles has a high moisture content. The wrapping paper can absorb a portion of the water from the aerosol, so that its strength is reduced. This can be partially prevented by using a wet strength agent.

[0040] Filling materials in the wrapping paper according to the invention can contribute to reducing discoloration of the wrapping paper. However, filling materials reduce the tensile strength of the wrapping paper, so that 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 45%, particularly preferably at least 0% and at most 35%, very particularly preferably at least 0% and at most 25%, each relative to the mass of the wrapping paper.

[0041] The filler material is preferably selected from calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talc and mixtures thereof. A particularly preferred filler material is bentonite, because like polyphosphates, it can absorb a large amount of water, thereby additionally contributing to flame retardancy. By using bentonite, the proportion of polyphosphate in the packaging paper can be within the lower range of the interval or preferred interval according to the present invention without negatively affecting the flame retardant effect.

[0042] According to the findings of the present inventors, sufficient flame retardancy can be obtained even by using bentonite alone, so that polyphosphate can be omitted completely.

[0043] In a preferred embodiment, the wrapper is coated or impregnated with a substance selected from the group consisting of starch, such as corn starch, potato starch or tapioca starch; starch derivatives, such as carboxymethyl starch or oxidized starch; cellulose derivatives, such as carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose and their salts; polysaccharides, such as alginates; polyvinyl alcohol; polyvinyl acetate; ethyl-vinyl acetate; gelatin; gums, such as gum arabic, guar gum, locust bean gum or tragacanth; or mixtures thereof. In this preferred embodiment, the proportion of these substances together is at least 0.1% and at most 20% 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 during storage or use of the aerosol-generating article and cause stains. Resistance to oil penetration can be determined according to TAPPI T559 cm-12 and expressed as a KIT level. In this preferred embodiment, the KIT level is at least 3 and at most 8.

[0044] When using starch or starch derivatives, it is recommended, depending on the type of application process, that the composition to be applied should not be introduced or applied to the paper together with the polyphosphates in a single process step, since the polyphosphates may cause agglomeration of the starch or starch derivative in the composition to be applied.

[0045] The basis weight of the wrapping paper can vary, with a higher basis weight generally also implying a higher tensile strength. With a higher basis weight, the wrapping paper will also become stiffer and more difficult to process, and the material requirements increase. Preferably, the basis weight of the wrapping paper according to the invention is therefore at least 15 g / m 2 And up to 120g / m 2 , particularly preferably at least 20 g / m 2 And up to 80g / m 2 The basis weight of packaging paper can be determined according to ISO 536:2019.

[0046] 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 some aerosol-generating articles for this reason. Preferably, the wrapping paper according to the invention has a thickness of at least 25 μm and at most 150 μm, particularly preferably at least 40 μm and at most 100 μm. The thickness can be determined on a single layer according to ISO 534:2011.

[0047] The tensile strength of the wrapping paper measured in the longitudinal direction is 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 high pulp fiber contents. 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.

[0048] 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 packaging paper, so it is advantageous if the packaging paper also has a corresponding strength in the wet state. Therefore, the wet tensile strength in the longitudinal direction is 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.

[0049] The air permeability of the wrapping paper may be low. Low air permeability is usually achieved by stronger refined pulp fibers. This also contributes to the increase in strength, so that preferably the air permeability is at least 0 cm 3 / (cm 2 ·min·kPa) and up to 80cm 3 / (cm 2 ·min·kPa), particularly preferably at least 0 cm 3 / (cm 2 ·min·kPa) and at most 30cm 3 / (cm 2 ·min·kPa). Air permeability can be determined according to ISO 2965:2019.

[0050] 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 90%. Preferably, the brightness is at least 80% and at most 95%, particularly preferably at least 83% and at most 90%.

[0051] 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.

[0052] In a preferred embodiment of the aerosol-generating article, the proportion of polyphosphate is higher on one side of the wrapper than on the other side, and the side with the higher proportion of polyphosphate faces or faces away from the aerosol-generating material. Thus, the choice of which of the two sides preferably faces the aerosol-generating material may depend on which side the aerosol-generating material is heated from.

[0053] In particularly preferred embodiments, the aerosol-generating article is an electrically heated article, wherein the heat originates from the aerosol-generating material, ie from the inside.

[0054] In this embodiment, for example, when the aerosol-generating article is inserted into the heating device, the ceramic tip equipped with the heating wire penetrates the aerosol-generating material. As a result, the highest temperature occurs inside the aerosol-generating article, and the wrapper is under a smaller thermal load, so that the proportion of polyphosphate can be selected to be lower; in particular, in this embodiment, the proportion of polyphosphate in the wrapper is at least 5% and at most 25% of the mass of the wrapper.

[0055] In another particularly preferred embodiment of the aerosol-generating article, the aerosol-generating article is an electrically heated article, wherein the heat is supplied from the outside through the wrapper.

[0056] In this embodiment, all heat must be conducted through the wrapping paper into the aerosol generating material, so that the heat load of the wrapping paper is higher, and therefore the proportion of polyphosphate in the wrapping paper can be selected to be higher; in particular, in this embodiment, the proportion of polyphosphate in the wrapping paper is at least 10% and at most 30% of the mass of the wrapping paper.

[0057] 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.

[0058] The packaging paper according to the invention can be manufactured according to the following method according to the invention, comprising steps A to G.

[0059] A – Suspending pulp fibers in an aqueous suspension,

[0060] B – Refining of suspended pulp fibers in a refining unit,

[0061] C—applying the suspension to a running web,

[0062] D – Forming a fiber web by dewatering the suspension,

[0063] E – pressed fiber web,

[0064] F – Drying fiber web,

[0065] G – Roll up the wrapping paper,

[0066] Between step F and step G, at least one composition containing one or more polyphosphates is applied to a fiber web, and the fiber web is dried to form a wrapping paper,

[0067] And wherein the wrapper from step G comprises pulp fibers and one or more polyphosphates, and the pulp fibers constitute at least 55% and at most 95% of the mass of the wrapper, and the polyphosphates together constitute at least 5% and at most 30% of the mass of the wrapper.

[0068] Preferably, the step of applying the composition comprising polyphosphate to the fiber web is performed by one or a combination of two or more of the following steps:

[0069] F.1 applying a composition comprising a polyphosphate to a fiber web in a size press of a paper machine,

[0070] F.2 applying the composition comprising polyphosphate to a fiber web on one side in a film press or in the coating unit of a paper machine, and

[0071] F.3 The polyphosphate-containing composition is applied to the fiber web on one side by printing, in particular by rotogravure printing, or by spraying.

[0072] In this regard, step F.1 is carried out in a size press, so that the fiber web is impregnated with a composition comprising polyphosphate. This variant offers advantages that can be easily realized. It usually results in a substantially uniform distribution of the polyphosphate over the thickness of the wrapping paper, so that relatively more polyphosphate is required to achieve the desired effect. However, it is also possible in fact to adjust the settings of the size press in this step so that the polyphosphate is unevenly distributed over the thickness of the fiber web and thus unevenly distributed over the thickness of the wrapping paper.

[0073] According to step F.2, the composition comprising polyphosphate is applied to one side of the fiber web in a film press or in a coating unit. This results in an inhomogeneous distribution of the polyphosphate over the thickness of the packaging paper, and a high flame retardant effect can be achieved with a smaller proportion of polyphosphate in the packaging paper.

[0074] According to step F.3, the composition comprising polyphosphate 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 in a rotogravure 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 machine, on which the application of the composition is carried out by printing or spraying. Although steps F.1 and F.2 are usually 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 machine.

[0075] 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 polyphosphate in a size press and in step F.3 a further composition comprising polyphosphate is printed on one side of the fiber web in a rotogravure printing unit. In this highly particularly preferred embodiment, the polyphosphate 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 again be significantly increased.

[0076] In a further highly particularly 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 particularly preferred embodiment, the packaging paper can be produced particularly efficiently, since, for example, all application units can be integrated into one paper machine.

[0077] Independently of using one or more of steps F.1, F.2 or F.3, the composition comprising polyphosphate 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.

[0078] The composition used in step F.1, F.2 or F.3 comprises a polyphosphate and a solvent, wherein the solvent is preferably water. The amount of polyphosphate in the composition may vary and depends on the type of application process, the amount of polyphosphate to be applied in the wrapping paper and the required amount. 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. In a preferred embodiment of the method, the composition may additionally contain carboxymethylcellulose, which fixes the polyphosphate in the fiber web as a binder and also increases the strength of the wrapping paper. In a particularly preferred embodiment, the composition contains at least 0.1% and at most 15% carboxymethylcellulose relative to the mass of the composition.

[0079] In a highly particularly preferred embodiment, one of steps F.1 or F.2 is carried out, and the fiber web is then dried, rolled up and unfolded again, followed by step F.3, wherein the fiber web in the dry, rolled-up state before step F.3 preferably contains polyphosphate in an amount of at least 4% and at most 20% of the mass of the fiber web in the dry and rolled-up state.

[0080] If steps F.1 , F.2 and / or F.3 are combined in any form, the polyphosphate-containing compositions used in steps F.1 , F.2 and / or F.3 may be identical or different.

[0081] In the wrapper after step G, pulp fibers account for at least 55% and at most 95% of the mass of the wrapper. In order to obtain an even better ratio between pulp fibers and polyphosphate, the proportion of pulp fibers may be at least 70% and at most 90%, and more particularly preferably at least 75% and at most 90%, each relative to the mass of the wrapper after step G.

[0082] The pulp fibers in step A are preferably derived from one or more plants selected from the group consisting of conifers, deciduous trees, annual plants, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, bamboo, ramie, abaca, sisal, kenaf and cotton. The pulp fibers may also be fibers produced in whole or in part from regenerated cellulose, such as Tencel. TM Fiber, Lyocell TM Fiber, Viscose or Modal TM fiber.

[0083] Preferably, the pulp fibers in step A are formed from pulp fibers from coniferous trees in a proportion of at least 25% and at most 100% relative to the mass of the pulp fibers, since these pulp fibers provide high strength to the packaging paper in step G.

[0084] The wrapper after step G contains one or more polyphosphates, wherein the polyphosphates together account for at least 5% and at most 30% of the mass of the wrapper. Preferably, the proportion of polyphosphates together in the wrapper is at least 8% and at most 27% of the mass of the wrapper, more particularly at least 9% and at most 25% of the mass of the wrapper.

[0085] In the context of the present invention, a polyphosphate is a salt having the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ] wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH4 + ).

[0086] Thus, this definition also includes compounds known as oligophosphates, which have the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1], and wherein the value of n is generally at least 2 and at most 10. In addition, the definition also includes mixtures of polyphosphates with different n values ​​or with different monovalent metals M or ammonium in the intervals or preferred intervals according to the invention, or mixtures of linear and cyclic polyphosphates. It is contemplated and also within the scope of the present invention that for polyphosphates with higher n values, for example greater than 10, there are mixtures of polyphosphates with different n values. In this context, mixtures of polyphosphates with different n values ​​fall within the definition, provided that the average value of n is within the intervals or preferred intervals according to the invention, wherein n is not necessarily an integer.

[0087] Polyphosphates having an n value of at least 3 and at most 80 are preferred, and n values ​​of at least 10 and at most 35 are particularly preferred.

[0088] Preferably, and independently of the choice of n, M is a monovalent metal selected from lithium, sodium and potassium or ammonium; particularly preferably, the monovalent metal is sodium.

[0089] Particularly preferably, the polyphosphate has an n value of at least 15 and at most 30, and the monovalent metal M is sodium. In particular, the polyphosphate comprises sodium hexametaphosphate.

[0090] In a preferred embodiment, after step G, the wrapper is a wrapper according to one of the preceding embodiments. DETAILED DESCRIPTION

[0091] Some preferred embodiments of the wrapping paper according to the invention will now be described.

[0092] The base paper for the wrapping paper according to the invention is produced 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 therein 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). The basis weight of the base paper is about 30 g / m 2 , and apart from the processing aids and additives customary in papermaking, it contains only pulp fibers and no filler materials. Through further steps, a total of 6 packaging papers according to the invention are produced from the base paper. These steps are also partly carried out in the paper machine during the production of the base paper.

[0093] In the size press of a paper machine, a fiber web is impregnated on both sides over the entire surface with a composition comprising water and polyphosphate, wherein n is from 23 to 30 and the monovalent metal M is sodium (step F.1), and then the fiber web is dried by contact with a heated drying cylinder. Finally, the fiber web is rolled up (step G). The concentration of polyphosphate in the composition is varied, so as to obtain different packaging papers according to the invention.

[0094] In a further step, a composition comprising water, sodium polyphosphate and carboxymethylcellulose is applied by a rotogravure printing process (step F.3) substantially over the entire surface of one side of the previously impregnated wrapping paper. Here again, the concentration of polyphosphate is varied, so that a total of six different wrapping papers P1 to P6 according to the invention are obtained. The amounts of polyphosphate after impregnation in the size press (step F.1) and after printing the composition (step F.3) are shown in Table 1.

[0095]

[0096] Table 1

[0097] It should be noted that the wrapper obtained after step F.1 already represents an embodiment according to the invention.

[0098] To test the flame retardant properties of the wrapping paper, the paper was held in a flame in an inclined position so that both sides of the paper were surrounded by the flame. For all wrapping papers, it was found that the paper became charred but did not burn, and no self-supporting smoldering process began.

[0099] Aerosol-generating articles were manufactured from wrappers P1 to P6 without any problems, making these wrappers suitable for use in aerosol-generating articles. No effect on the taste of the aerosol-generating articles could be detected.

[0100] Another wrapping paper according to the present invention uses a 20 g / m2 wrapping paper made of pulp fibers and without filler material. 2 The base paper is made of a base paper which is impregnated on both sides over the entire surface in a size press with a composition comprising water and polyphosphate (step F.1) so that it then contains 8% of polyphosphate relative to the mass of the wrapping paper. The wrapping paper is connected to another paper layer by lamination. The other paper layer has a 24 g / m 2 basis weight, a filler content of 28% relative to the mass of the paper layer and a 75cm 3 / (cm 2 ·min·kPa). For this wrapping paper, a good flame retardant effect was also found. An aerosol-generating article was produced and after use, it could be clearly recognized that the discoloration of the wrapping paper was substantially less noticeable due to the additional paper layer on the outside.

[0101] Another wrapping paper according to the present invention uses 30g / m 2A base paper is produced according to the invention, wherein the base paper comprises pulp fibers and further comprises bentonite as a filler material in an amount of about 34% relative to the mass of the base paper. The base paper is impregnated in a size press on both sides over the entire surface with a composition comprising water and polyphosphate (step F.1), so that it then comprises about 5% polyphosphate. Despite the low polyphosphate content, a good flame retardant effect can be discerned. The inventors believe that the high water content of the bentonite contributes to the flame retardant effect.

[0102] Aerosol-generating articles were made from such wrappers according to the invention and it was found that due to the lower polyphosphate content, discoloration of the wrapper was less noticeable.

[0103] Therefore, the wrapping paper according to the present invention is very suitable for use in aerosol-generating articles and has good biodegradability and flame retardant effect, which is a better combination of properties than comparable wrapping papers in the prior art.

Claims

1. An aerosol-generating article comprising a wrapper and an aerosol-generating material, wherein the wrapper encloses the aerosol-generating material and during the intended use of the aerosol-generating article, the aerosol-generating material is only heated but not burned, wherein the wrapper comprises pulp fibers and one or more polyphosphates, wherein the pulp fibers account for at least 70% and at most 95% of the mass of the wrapper, and the polyphosphates are contained together in a concentration of at least 5% and at most 30% relative to the mass of the wrapper, wherein the polyphosphates are of formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ] wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH4 + ).

2. An aerosol-generating article according to claim 1, wherein the proportion of pulp fibres in the wrapper is at least 70% and at most 90%, each relative to the mass of the wrapper.

3. An aerosol-generating article according to claim 1 or 2, wherein the proportion of pulp fibres in the wrapper is at least 75% and at most 90%, each 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 the group consisting of conifers, deciduous trees, annual plants, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, bamboo, abaca, sisal, kenaf and cotton.

5. 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.

6. An aerosol-generating article according to claim 5, wherein the pulp fibers are made in whole or in part from Tencel TM Fiber, Lyocell TM Fiber, Viscose or Modal TM Fiber formation.

7. An aerosol-generating article according to claim 1 or 2, wherein the pulp fibres originate from coniferous trees in a proportion of at least 25% and at most 100% relative to the mass of the pulp fibres.

8. An aerosol-generating article according to claim 1 or 2, wherein the proportion of polyphosphate in the wrapper is at least 8% and at most 27% by mass of the wrapper.

9. An aerosol-generating article according to claim 8, wherein the proportion of polyphosphate in the wrapper is at least 9% and at most 25% by mass of the wrapper.

10. An aerosol-generating article according to claim 1 or 2, wherein for the polyphosphate, the molecular formula M n+ 2P n O 3n+1 or M n [H2P n O 3n+1 ]The value n in is at least 3 and at most 80.

11. An aerosol-generating article according to claim 10, wherein for the polyphosphate, the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ]The value n in is at least 10 and at most 35.

12. An aerosol-generating article according to claim 1 or 2, wherein for the polyphosphate, the molecular formula M n+ 2P n O 3n+1 or M n [H2P n O 3n+1 ] wherein the monovalent metal M is selected from lithium, sodium and potassium.

13. An aerosol-generating article according to claim 1 or 2, wherein for the polyphosphate, the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ] wherein the value of n is at least 15 and at most 30, and the monovalent metal M is sodium.

14. An aerosol-generating article according to claim 1 or 2, wherein the polyphosphate comprises sodium hexametaphosphate.

15. An aerosol-generating article according to claim 1 or 2, wherein during intended use, a side of the wrapper facing or facing away from the aerosol-generating material comprises a higher proportion of polyphosphate than another side of the wrapper.

16. An aerosol-generating article according to claim 1 or 2, wherein the polyphosphate is evenly distributed over at least 70% of the surface area of ​​the wrapper.

17. An aerosol-generating article according to claim 16, wherein the polyphosphate is evenly distributed over at least 90% of the surface area of ​​the wrapper.

18. An aerosol-generating article according to claim 1 or 2, wherein the wrapper is connected to another layer of material by gluing.

19. An aerosol-generating article according to claim 18, wherein the further layer of material is a layer of aluminium foil, plastic foil, a foil made from regenerated cellulose or a foil made from cellulose hydrate.

20. An aerosol-generating article according to claim 18, wherein the another layer of material is a layer of paper.

21. An aerosol-generating article according to claim 20, wherein the paper layer comprises pulp fibers and white filler particles, and the white filler particles account for at least 15% and at most 45% of the mass of the paper layer, and the paper layer faces away from the aerosol-generating material during intended use.

22. An aerosol-generating article according to claim 20, wherein the paper layer has a thickness of at least 5 cm measured according to ISO 2965:2019. 3 / (cm 2 ·min·kPa) and up to 30000cm 3 / (cm 2 ·min·kPa), and the basis weight of the paper layer is at least 10g / m 2 And up to 30g / m 2 .

23. An aerosol-generating article according to claim 20, wherein the paper layer has a viscosity of at least 30 g / m 2 And up to 100g / m 2 The basis weight.

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

25. An aerosol-generating article according to claim 24, wherein the proportion of filler material is at least 0% and at most 45%, each relative to the mass of the wrapper.

26. An aerosol-generating article according to claim 25, wherein the proportion of filler material is at least 0% and at most 35%, each relative to the mass of the wrapper.

27. An aerosol-generating article according to claim 25, wherein the proportion of filler material is at least 0% and at most 25%, each relative to the mass of the wrapper.

28. An aerosol-generating article according to claim 24, 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, bentonite, and mixtures thereof.

29. An aerosol-generating article according to claim 1 or 2, wherein the wrapper is coated or impregnated with a substance selected from the group consisting of: corn starch, potato starch or tapioca starch; starch derivatives; cellulose derivatives and their salts; polyvinyl alcohol; polyvinyl acetate; ethylene vinyl acetate; gelatin; gums; or mixtures thereof.

30. An aerosol-generating article according to claim 1 or 2, wherein the wrapper is coated or impregnated with a material selected from the group consisting of: polysaccharides; polyvinyl alcohol; polyvinyl acetate; ethylene vinyl acetate; gelatin; gum; or mixtures thereof.

31. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a KIT level of at least 3 and at most 8 as measured according to TAPPIT 559 cm-12.

32. An aerosol-generating article according to claim 1 or 2, wherein the basis weight of the wrapper is at least 15 g / m 2 And up to 120g / m 2 .

33. An aerosol-generating article according to claim 32, wherein the wrapper has a basis weight of at least 20 g / m 2 And up to 80g / m 2 .

34. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has a thickness of at least 25 μm and at most 150 μm.

35. An aerosol-generating article according to claim 34, wherein the wrapper has a thickness of at least 40 μm and at most 100 μm.

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

37. An aerosol-generating article according to claim 36, wherein the wrapper has a tensile strength in the longitudinal direction of at least 20 N / 15 mm and at most 80 N / 15 mm.

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

39. An aerosol-generating article according to claim 38, wherein the wrapper has a wet tensile strength in the longitudinal direction of at least 2 N / 15 mm and at most 8 N / 15 mm according to ISO 12625-5:2016.

40. An aerosol-generating article according to claim 1 or 2, wherein the wrapper has an air permeability of at least 0 cm 3 / (cm 2 ·min·kPa) and up to 80cm 3 / (cm 2 ·min·kPa).

41. An aerosol-generating article according to claim 40, wherein the wrapper has an air permeability of at least 0 cm 3 / (cm 2 ·min·kPa) and at most 30cm 3 / (cm 2 ·min·kPa).

42. An aerosol-generating article according to claim 1 or 2, wherein the opacity of the wrapper is at least 40% and at most 90%, and / or the brightness of the wrapper is at least 80% and at most 95%.

43. An aerosol-generating article according to claim 42, 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%.

44. An aerosol-generating article according to claim 1 or 2, wherein the proportion of polyphosphate on one side of the wrapper is higher than the proportion of polyphosphate on the other side, and the side with the higher proportion of polyphosphate faces or faces away from the aerosol-generating material.

45. An aerosol generating article according to claim 1 or 2, wherein the aerosol generating article is an electrically heated aerosol generating article, and the material of the aerosol generating article is heated from the inside during its intended use, and the wrapping paper contains a polyphosphate in an amount of at least 5% and at most 25% relative to the mass of the wrapping paper.

46. ​​An aerosol generating article according to claim 1 or 2, wherein the aerosol generating article is an electrically heated aerosol generating article, and the aerosol generating material of the aerosol generating article is heated from the outside during its intended use, and the wrapping paper contains a polyphosphate in an amount of at least 10% and at most 30% relative to the mass of the wrapping paper.

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