Aerosol-generating items

Abstract

A wrapper paper suitable for use in an aerosol-generating article is described that includes pulp fibers and one or more polyphosphates, wherein the pulp fibers constitute at least 55% and at most 95% by weight of the wrapper paper, and the polyphosphates are present in a combined concentration of at least 5% and at most 30% by weight of the wrapper paper. In this regard, the polyphosphates are represented by 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 (NH + )

Description

[Technical Field]

[0001] The present invention relates to a wrapper paper for an aerosol-generating article, which is relatively heat-resistant, thus still having sufficient mechanical strength to allow the article to be handled without problems after use, and which also has a flame-retardant effect so that the aerosol-generating article made from the wrapper paper cannot be smoked like a smoking article. The wrapper paper according to the present invention has improved flame retardancy compared to known heat-resistant wrapper papers. This is achieved by the high content of a specific polyphosphate salt in the wrapper paper. [Background technology]

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

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

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

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

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

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

[0008] It is therefore of interest to have available a wrapper paper that still has sufficient tensile strength after heating, is biodegradable, and has particularly efficient flame retardant effect. Furthermore, the design of a wrapper paper for an aerosol-generating article must take into account, among other things, regulatory restrictions, toxicology, and the effect of the wrapper paper on the taste of the aerosol-generating article. [Prior art documents] [Patent documents]

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

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

[0011] An aerosol-generating article in the context of the present invention is a rod-shaped article comprising an aerosol-generating material and a wrapper paper enclosing the aerosol-generating material, wherein the aerosol-generating material is heated but not combusted during intended use. For typical aerosol-generating materials, such as tobacco materials, heating without combustion occurs when the aerosol-generating material is heated to temperatures of up to 400°C. [Means for solving the problem]

[0012] This object is achieved by a wrapper paper for an aerosol-generating article according to claim 1, an aerosol-generating article comprising this wrapper paper according to claim 30, the use of such a wrapper paper for an aerosol-generating article according to claim 34, and a method for producing a wrapper paper according to the invention according to claim 35. Further advantageous embodiments are provided in the dependent claims.

[0013] The inventors have found that this object can be achieved by a wrapper paper suitable for use in an aerosol-generating article, comprising pulp fibers and one or more polyphosphates, wherein the pulp fibers constitute at least 55% and at most 95% by weight of the wrapper paper, and the polyphosphates together comprise a concentration of at least 5% and at most 30% by weight of the wrapper paper.

[0014] According to the findings of the present inventors, a high pulp fiber content is necessary to obtain high strength in wrapper paper. Additives such as the polyphosphate of the present invention may prevent the formation of hydrogen bonds between pulp fibers, thus reducing the strength of the wrapper paper. However, a high concentration of polyphosphate may be required to obtain good flame retardant effect, which necessitates a high proportion of pulp fiber in the wrapper paper. Therefore, only a few additional ingredients can be included in the wrapper paper. In particular, ingredients that further reduce strength are undesirable.

[0015] Only the combination of a high pulp fiber content and a suitably selected concentration of polyphosphate allows the production of a wrapper paper with such high tensile strength after heating due to its high initial strength, and such a wrapper paper that the aerosol-generating article made from the wrapper paper can be removed from the heating device without any problems or risk of the heat source incorporated in the aerosol-generating article falling off. Furthermore, due to the high flame retardant effect, the aerosol-generating article cannot be smoked like a cigarette.

[0016] The wrapper paper components further provide excellent biodegradability and very good processability during the manufacture of the aerosol-generating article.

[0017] For its strength, the wrapper paper requires pulp fibers to constitute at least 55% and at most 95% of the mass of the wrapper paper. To obtain an even better ratio between pulp fibers and polyphosphate, the proportion of pulp fibers can be preferably at least 70% and at most 90%, particularly preferably at least 75% and at most 90%, respectively, relative to the mass of the wrapper paper.

[0018] The pulp fibers are preferably sourced from one or more plants selected from the group consisting of conifers, deciduous trees, annuals, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, ramie, bamboo, abaca, sisal, kenaf and cotton. The pulp fibers may also be formed wholly or partly by fibers made from regenerated cellulose, such as Tencel® fibers, Lyocell® fibers, viscose fibers or Modal® fibers.

[0019] Preferably, the pulp fibers are formed from pulp fibers of softwood origin in a proportion of at least 25% and at most 100% by mass of the pulp fibers, since these pulp fibers provide the wrapper paper with high strength.

[0020] The wrapper paper comprises one or more polyphosphates, which together constitute at least 5% and at most 30% of the wrapper paper's mass. The inventors have found that the polyphosphates protect the pulp fibers within the paper structure from excessive oxidation. Furthermore, the inventors have found that the polyphosphates are highly hygroscopic, thus adsorbing water to the paper. When the paper is heated, the water is first removed from the polyphosphates, thereby limiting the temperature of the pulp fibers. Because the heating process is time-limited during normal use of an aerosol-generating article, lasting no more than a few minutes, and especially only a few seconds when attempting to ignite the aerosol-generating article, the adsorbed water in the polyphosphates substantially contributes to providing a flame-retardant effect. This provides an advantage over wrapper papers known in the art.

[0021] The flame retardant effect increases with increasing concentration of polyphosphate, but the strength of the wrapper paper decreases, especially after heating. Therefore, preferably, the proportion of polyphosphate in the wrapper paper together is at least 8% and at most 27% by weight of the wrapper paper, in particular at least 9% and at most 25% by weight of the wrapper paper.

[0022] In the context of the present invention, polyphosphates have the molecular formula M n+2 P n O 3n+1 or Mn [H2P n O 3n+1 wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH + )

[0023] Therefore, this definition includes the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1 ], where n is typically at least 2 and at most 10. This definition also includes mixtures of polyphosphates having different values ​​of n within the intervals or preferred intervals according to the invention, or having different monovalent metals M or ammonium, or mixtures of linear and cyclic polyphosphates. For polyphosphates with higher values ​​of n, e.g., greater than 10, mixtures of polyphosphates with different values ​​of n are expected and are also within the scope of the invention. In this context, mixtures of polyphosphates with different values ​​of n fall within the definition, provided that the average value of n is within the intervals or preferred intervals according to the invention, and that n is not necessarily an integer.

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

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

[0026] More particularly preferably, the polyphosphate has a value of n 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 inventors' findings, it is important to know how the polyphosphate is distributed throughout the thickness of the wrapper paper. Generally, a good flame retardant effect can be achieved when the polyphosphate is distributed substantially uniformly in the wrapper paper. However, in a preferred embodiment, the wrapper paper is designed so that the side of the wrapper paper facing the aerosol-generating material or facing away from the aerosol-generating material contains a higher proportion of polyphosphate than the other side of the wrapper paper. Preferably, the polyphosphate content is higher on the side of the wrapper paper on which the aerosol-generating article manufactured from the wrapper paper is heated because this side is exposed to a higher thermal load. Therefore, a higher polyphosphate content on this side of the wrapper paper can contribute particularly well to the flame retardant effect. In this way, the proportion of polyphosphate in the wrapper paper can be reduced without loss of flame retardant effect, and therefore the proportion of pulp fiber in the wrapper paper can be increased at the same basis weight, resulting in an overall increase in the strength of the wrapper paper. Alternatively, with this preferred distribution of polyphosphate in the wrapper paper, the basis weight can be reduced without loss in flame retardant effectiveness, thereby reducing material requirements.

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

[0029] Preferably, the polyphosphate is substantially uniformly distributed over at least 70% of the surface area of ​​the wrapper paper, particularly preferably over at least 95% of the surface area, variations in the proportion of polyphosphate within these areas occurring only due to manufacturing and not intentionally, and in this context, this uniform distribution refers to a distribution over the surface, but not a distribution through the thickness.

[0030] For various reasons, the wrapper paper is preferably bonded to an additional layer of material, in particular a paper layer. This bond is preferably formed by adhesive bonding, but any type of bond is possible. In particular, it may be sufficient for the wrapper paper and the additional layer to be placed on top of each other during the manufacture of the aerosol-generating article, one on top of the other, and rolled up together so as to encase the aerosol-generating material together. The additional layer can be applied to either of the two sides of the wrapper paper, facing or facing away from the aerosol-generating material of the aerosol-generating article manufactured from the wrapper paper, depending on the desired effect.

[0031] If the wrapper paper is bonded to one or more paper layers or indeed to layers of other materials such as aluminum foil, plastic foil, foil made from cellulose hydrate (such as Cellophane®) and the like, the above requirements regarding the proportion of pulp fibres and polyphosphate and all further properties mentioned below apply only to the wrapper paper itself and not to any further layers bonded to the wrapper paper, unless expressly mentioned.

[0032] One reason for bonding the wrapper paper to an additional layer may be that, for example, polyphosphates darken the wrapper paper under thermal load. This drawback can be overcome by bonding the wrapper paper to an additional layer of material such that the wrapper paper according to the present invention faces the aerosol-generating material and the additional layer is located on the side facing away from the aerosol-generating material. Under thermal load, this additional layer then covers the wrapper paper, so that the color visible from the outside does not change or changes only slightly.

[0033] Therefore, in this particularly preferred embodiment, the wrapper paper is bonded to an additional paper layer comprising pulp fibers and white filler particles, the white filler particles constituting 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 impart a white color and high opacity to the paper layer, so that discoloration of the underlying wrapper paper according to the invention is not visible or is only slightly visible.

[0034] A further reason for bonding the wrapper paper to an additional layer of material is, for example, to prevent stain formation on the wrapper paper. The aerosol-generating material may contain oils, such as flavorings, that penetrate the wrapper paper during storage or heating and cause stains. This problem can be overcome by bonding the wrapper paper to an additional layer of material.

[0035] Therefore, in this particularly preferred embodiment, the wrapper paper is bonded to an additional paper layer, the additional paper layer having a thickness of at least 5 cm, measured according to ISO 2965:2019. 3 / (cm 2 ·min·kPa) and up to 30000 cm 3 / (cm 2 ·min·kPa) and the basis weight of the additional paper layer is at least 10 g / m 2 and a maximum of 30 g / m2. The air permeability of the additional paper layer is the result of a porous structure that prevents the migration of oil or other components through the paper layer.

[0036] A further reason for bonding the wrapper paper to an additional layer of material is, for example, to increase the stiffness of the wrapper paper. Because aerosol-generating articles often have hollow spaces inside, consumers may accidentally compress the aerosol-generating article while handling it, thereby deforming the aerosol-generating article to the point that it can no longer be inserted into, for example, a heating appliance. A wrapper paper bonded to an additional layer with high stiffness can prevent this.

[0037] Therefore, in this particularly preferred embodiment, the wrapper paper is bonded to an additional paper layer, the additional paper layer having a thickness of at least 30 g / m 2 and up to 100g / m 2 , since this also results in high bending stiffness.

[0038] Although a paper layer is generally preferred for the additional layer provided in the wrapper paper due to its good biodegradability and for other reasons mentioned above, the additional layer can also be formed, less preferably, by aluminum foil, plastic foil or foil made from regenerated cellulose, such as cellulose hydrate (Cellophane®).

[0039] The wrapper paper according to the present invention, or additional paper layers to which it is bonded for the aforementioned or other reasons, can contain additional ingredients, such as fillers, sizing agents, wet strength agents, additives, processing aids, humectants, and flavoring agents. Those skilled in the art can select these ingredients empirically. In particular, wet strength agents can be advantageous for use in aerosol-generating articles because the aerosol formed during use of the aerosol-generating article has a high moisture content. The wrapper paper can absorb some of the water from the aerosol, resulting in a decrease in its strength. This can be partially prevented by the use of wet strength agents.

[0040] The filler material in the wrapper paper according to the present invention can contribute to reducing discoloration of the wrapper paper.However, since the filler material reduces the tensile strength of the wrapper paper, its proportion should not be too high.Therefore, preferably, the proportion of the filler material in the wrapper paper is at least 0% and at most 45%, particularly preferably at least 0% and at most 35%, more particularly preferably at least 0% and at most 25%, based on the mass of the wrapper paper.

[0041] The filler material is preferably selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talcum, and mixtures thereof. A particularly preferred filler material is bentonite, because, like polyphosphates, bentonite can absorb large amounts of water, thereby further contributing to flame retardancy. By using bentonite, the proportion of polyphosphate in the wrapper paper can be lower in the range or preferred range according to the invention, without adversely affecting the flame retardant effect.

[0042] According to the inventors' findings, it is even possible to obtain sufficient flame retardancy by using bentonite alone, so that polyphosphates may be completely unnecessary.

[0043] In a preferred embodiment, the wrapper paper is coated or impregnated with a material selected from the group consisting of starches such as corn starch, potato starch, or tapioca starch; starch derivatives such as carboxymethyl starch or oxidized starch; cellulose derivatives and salts thereof, such as carboxymethylcellulose, methylcellulose, and hydroxymethylcellulose; polysaccharides such as alginates; polyvinyl alcohol; polyvinyl acetate; ethyl vinyl acetate; gelatin; gums such as gum arabic, guar gum, locust bean gum, or tragacanth gum; or mixtures thereof. In this preferred embodiment, the combined proportion of these materials is at least 0.1% and at most 20% by weight of the wrapper paper. This preferred embodiment provides an additional advantage of resistance to oil penetration. The aerosol-generating material may contain oils, such as flavorings, that penetrate the wrapper paper and cause staining during storage or use of the aerosol-generating article. Resistance to oil penetration can be determined according to TAPPI T 559cm-12 and is 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, depending on the type of application process, it is recommended that the composition to be applied is not introduced or applied to the paper in a single process step together with the polyphosphate, since the polyphosphate may cause agglomeration of the starch or starch derivative in the composition to be applied.

[0045] The basis weight of the wrapper paper can vary, with higher basis weight generally also meaning higher tensile strength. At higher basis weights, the wrapper paper also becomes stiffer, more difficult to process and increases material requirements. Therefore, preferably, the basis weight of the wrapper paper according to the present invention is at least 15 g / m 2 and up to 120 g / m 2 , particularly preferably at least 20 g / m 2 and up to 80 g / m 2 The basis weight of the wrapper paper can be determined according to ISO 536:2019.

[0046] The thickness of the wrapper paper mainly affects the bending stiffness and heat transfer within the wrapper paper. A high bending stiffness is advantageous because the aerosol-generating article made from the wrapper paper is less likely to deform, but on the other hand, a high bending stiffness may cause problems due to the restoring force when the aerosol-generating material is wrapped in the wrapper paper. A high thickness slows down the heat transfer through the wrapper paper and is therefore advantageous for some aerosol-generating articles. Preferably, the thickness of the wrapper paper according to the present invention is 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 for a single layer in accordance with ISO 534:2011.

[0047] The tensile strength of the wrapper 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. Higher tensile strength can be achieved by a higher pulp fiber content. However, this also means higher material requirements, and for that reason, it does not make sense to aim for a particularly high tensile strength. The preferred range allows for a particularly advantageous combination of problem-free processability and material requirements. Tensile strength can be determined in accordance with ISO 1924-2:2008.

[0048] Because aerosol-generating materials often contain humectants, the aerosol generated during heating has a relatively high moisture content. This moisture can reduce the strength of the wrapper paper, and for this reason, it is advantageous for the wrapper paper to also have a corresponding wet strength. Therefore, the longitudinal wet tensile strength is preferably at least 1 N / 15 mm and at most 10 N / 15 mm, particularly preferably at least 2 N / 15 mm and at most 8 N / 15 mm. The longitudinal wet tensile strength can be determined in accordance with ISO 12625-5:2016.

[0049] The wrapper paper can have low air permeability. Low air permeability is often achieved by more thorough refining of the pulp fibers. This also contributes to improved strength, so the air permeability is preferably at least 0 cm 3 / (cm 2 ·min·kPa) and up to 80cm 3 / (cm 2 ·min ·kPa), particularly preferably at least 0 cm 3 / (cm 2 ·min·kPa) and up to 30cm 3 / (cm 2 ·min·kPa). Air permeability can be determined according to ISO 2965:2019.

[0050] When the wrapper paper according to the present invention is visible from the outside to the aerosol-generating article, optical properties can be important. Generally, high opacity and high brightness are desired. Both properties can be substantially influenced by the type and amount of filler material in the wrapper paper. Preferably, the opacity is at least 40% and at most 90%, particularly preferably at least 45% and at most 90%. Preferably, the brightness is at least 80% and at most 95%, particularly preferably at least 83% and at most 90%.

[0051] Aerosol-generating articles can be produced from the wrapper paper according to the present invention according to methods known in the art. Thus, an aerosol-generating article according to the present invention comprises an aerosol-generating material and a wrapper paper according to one of the above-described embodiments, the wrapper paper enclosing the aerosol-generating material.

[0052] In a preferred embodiment of the aerosol-generating article, the proportion of polyphosphate is higher on one side of the wrapper paper than on the other side, and the side with the higher proportion of polyphosphate faces the aerosol-generating material 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 the side on which the aerosol-generating material is heated.

[0053] In a particularly preferred embodiment, the aerosol-generating article is an electrically heated article, and heating occurs from the aerosol-generating material, i.e. from the inside.

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

[0055] In a further particularly preferred embodiment of the aerosol-generating article, the aerosol-generating article is an electrically heated article, and heating is effected from the outside through the wrapper paper.

[0056] In this embodiment, the heat load on the wrapper paper is higher because all of the heat must be conducted through the wrapper paper to the aerosol-generating material, and therefore a higher proportion of polyphosphate in the wrapper paper may be selected, particularly in this embodiment, the proportion of polyphosphate in the wrapper paper is at least 10% and at most 30% by mass of the wrapper paper.

[0057] The wrapper paper according to the invention can be advantageously used in aerosol-generating articles, and for that reason the use of the wrapper paper according to the invention in aerosol-generating articles is also an object of the present invention.

[0058] The wrapper paper according to the present invention can be produced according to the following method according to the present invention, the method comprising steps A to G: A - suspending pulp fibers in an aqueous suspension; B—purifying the suspended pulp fibers in a refining unit; C—applying the suspension to the running wire; D—forming a fibrous web by dewatering the suspension; E—pressing the fiber web; F—Drying the fiber web; G—rolling up the fiber web; Between steps F and G, at least one composition containing one or more polyphosphates is applied to the fibrous web and the fibrous web is dried to form a wrapper paper, the wrapper paper from step G comprising pulp fibers and one or more polyphosphates, the pulp fibers comprising at least 55% and at most 95% of the mass of the wrapper paper, and the polyphosphates collectively comprising at least 5% and at most 30% of the mass of the wrapper paper.

[0059] Preferably, the step of applying the polyphosphate-containing composition to the fibrous web is carried out by one or a combination of two or more of the following steps:

[0060] F.1 applying a composition comprising polyphosphate to a fibrous web at a size press of a paper machine; F.2 Single-sided application of a composition containing polyphosphate to a fibrous web in the film press or coating unit of a paper machine; and F.3 Single-sided application of a composition containing polyphosphate to a fibrous web by printing, in particular by rotary gravure printing or spraying.

[0061] In this respect, step F.1 is carried out in a size press, so that the fibrous web is impregnated with a composition containing polyphosphate. This variant has the advantage that it is easy to carry out. Generally, a substantially uniform distribution of polyphosphate is achieved throughout the thickness of the wrapper paper, so that a relatively large amount of polyphosphate is required to achieve the desired effect. However, in practice, it is also possible to adjust the settings of the size press in this step, so that the polyphosphate is distributed unevenly throughout the fibrous web, and thus the thickness of the wrapper paper.

[0062] According to step F.2, a composition containing polyphosphate is applied to one side of the fibrous web in a film press or coating unit, which results in a non-uniform distribution of the polyphosphate throughout the thickness of the wrapper paper, allowing a lower proportion of polyphosphate in the wrapper paper to achieve a high flame retardant effect.

[0063] According to step F.3, the polyphosphate-containing composition is applied to one side of the fibrous web by printing or spraying; in a particularly preferred embodiment, the composition is printed on one side of the fibrous web in a rotary gravure printing unit. In this regard, the fibrous web is preferably dried, wound up, and unwound again before step F.3. The fibrous web can then be transported in a wound state to a further machine, where the composition is applied by printing or spraying. Steps F.1 and F.2 are typically carried out on the same paper machine on which the wrapper paper is produced, while the application according to step F.3 is typically carried out on a separate machine.

[0064] In a very particularly preferred embodiment, steps F.1 and F.3 are combined, so that first, in step F.1, the fibrous web is impregnated with a composition containing polyphosphate in a size press, and in step F.3, a further composition containing polyphosphate is printed on one side of the fibrous web in a rotogravure printing unit. In this more particularly preferred embodiment, the polyphosphates are both distributed in the wrapper paper and are present in a higher concentration on one side of the wrapper paper, so that the flame retardant effect can again be significantly increased.

[0065] In a further very particularly preferred embodiment, steps F.1 and F.2 are combined, with step F.1 taking place in a size press and step F.2 taking place in a coating unit. In this very particularly preferred embodiment, the wrapper paper can be produced particularly efficiently, since for example all coating units can be integrated into one paper machine.

[0066] Regardless of whether step F.1, F.2 or F.3 is used, the polyphosphate-containing composition is preferably applied to at least 70% of the surface area of ​​the wrapper paper, particularly preferably to at least 95% of the surface area of ​​the wrapper paper.

[0067] The composition used in step F.1, F.2, or F.3 contains a polyphosphate salt and a solvent, preferably water. The amount of polyphosphate salt in the composition can vary and depends on the type of coating process, the coating amount, and the desired amount of polyphosphate salt in the wrapper paper. Those skilled in the art can determine a suitable composition with these considerations in mind and design the coating process accordingly. In a preferred embodiment of the method, the composition can further contain carboxymethylcellulose, which acts as a binder to fix the polyphosphate salt in the fiber web and also improve the strength of the wrapper paper. In a particularly preferred embodiment, the composition contains at least 0.1% and up to 15% carboxymethylcellulose by weight of the composition.

[0068] In a very particularly preferred embodiment, one of steps F.1 or F.2 is carried out, then the fibrous web is dried, wound up and unwound again, then step F.3 is carried out, the dried, wound-up fibrous web before step F.3 preferably containing polyphosphate in an amount of at least 4% and at most 20% by weight of this dried, wound-up fibrous web.

[0069] When steps F.1, F.2 and / or F.3 are combined in any manner, the polyphosphate-containing compositions used in steps F.1, F.2 and / or F.3 can be the same or different.

[0070] In the wrapper paper after step G, the pulp fibers constitute at least 55% and at most 95% of the mass of the wrapper paper. To obtain an even better ratio between pulp fibers and polyphosphate, the proportion of pulp fibers can be at least 70% and at most 90%, particularly preferably at least 75% and at most 90%, respectively, relative to the mass of the wrapper paper after step G.

[0071] The pulp fibers of step A are preferably sourced from one or more plants selected from the group consisting of conifers, deciduous trees, annuals, spruce, pine, fir, beech, birch, eucalyptus, flax, hemp, jute, bamboo, ramie, abaca, sisal, kenaf, and cotton. The pulp fibers can also be fibers made in whole or in part from regenerated cellulose, such as Tencel® fibers, Lyocell® fibers, viscose fibers, or Modal® fibers.

[0072] Preferably, the pulp fibers in step A are formed from pulp fibers of softwood origin in a proportion of at least 25% and at most 100% by mass of the pulp fibers, since these pulp fibers provide a wrapper paper in step G with high strength.

[0073] The wrapper paper after step G comprises one or more polyphosphates, the polyphosphates together constituting at least 5% and at most 30% of the mass of the wrapper paper. Preferably, the combined proportion of polyphosphates in the wrapper paper is at least 8% and at most 27% of the mass of the wrapper paper, more particularly preferably at least 9% and at most 25% of the mass of the wrapper paper.

[0074] Polyphosphates in the context of the method according to the invention are those 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 (NH + )

[0075] Therefore, this definition includes the molecular formula M n+2 P n O 3n+1 or M n [H2P n O 3n+1

[0039] Also included are compounds known as oligophosphates, having a value of n typically of at least 2 and at most 10. This definition also includes mixtures of polyphosphates having different values ​​of n within the intervals or preferred intervals according to the invention, or having different monovalent metals M or ammonium, or mixtures of linear and cyclic polyphosphates. For polyphosphates with higher values ​​of n, e.g., greater than 10, mixtures of polyphosphates with different values ​​of n are expected and within the scope of the invention. In this regard, mixtures of polyphosphates with different values ​​of n fall within the definition, provided that the average value of n is within the intervals or preferred intervals according to the invention, and that n is not necessarily an integer.

[0076] Polyphosphates with a value of n of at least 3 and at most 80 are preferred, with polyphosphates with a value of n of at least 10 and at most 35 being particularly preferred.

[0077] Preferably, regardless of the selection of n, M is a monovalent metal selected from the group consisting of lithium, sodium and potassium, or ammonium. Particularly preferably, the monovalent metal is sodium.

[0078] Particularly preferably, the polyphosphate has a value of n of at least 15 and at most 30, and the monovalent metal M is sodium. In particular, the polyphosphate is sodium hexametaphosphate.

[0079] In a preferred embodiment, after step G the wrapper paper is a wrapper paper according to one of the previous embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0080] Some preferred embodiments of the wrapper paper according to the present invention will now be described.

[0081] Base paper for wrapper paper according to the invention was produced on a Fourdrinier paper machine. For this purpose, pulp fibers were suspended in water (step A) and refined in a refining unit (step B). The suspension was then applied to a running wire (step C) where it was dewatered to form a fibrous web (step D). To further dewater the fibrous web, it was pressed (step E) and dried in contact with heated drying cylinders (step F). The grammage of the base paper was about 30 g / m 2 and contained only pulp fibers and no filler material, except for the usual processing aids and additives in papermaking. A total of six wrapper papers according to the invention were produced from the base paper by further steps, which were also partly carried out on the paper machine during the production of the base paper.

[0082] In the size press of the paper machine, both sides of the fibrous web were impregnated with a composition comprising water and polyphosphate, where n is between 23 and 30, and the monovalent metal M is sodium (step F.1), and then the fibrous web was dried by contacting it with a heated drying cylinder. Finally, the fibrous web was rolled up (step G). The concentration of polyphosphate in the composition was varied to obtain different wrapper papers according to the present invention.

[0083] In a further step, a composition comprising water, sodium polyphosphate and carboxymethylcellulose was applied to substantially the entire surface of one side of the pre-impregnated wrapper paper by a rotary gravure printing process (step F.3). Again, the concentration of polyphosphate was varied so as to obtain a total of six different wrapper papers P1 to P6 according to the invention. The amounts of polyphosphate after impregnation in the size press (step F.1) and after printing of the composition (step F.3) are shown in Table 1.

[0084] [Table 1]

[0085] It should be noted that the wrapper paper obtained after step F.1 already represents an embodiment according to the invention.

[0086] To test the flame retardancy of the wrapper papers, the paper was held in a flame in an inclined position so that both sides of the paper were surrounded by flame. It was found that for all wrappers, the paper charred but did not burn and a self-sustaining smoking process did not begin.

[0087] Aerosol-generating articles were produced without issue from the paper wrappers P1-P2, and so these wrappers are suitable for use in aerosol-generating articles. No detectable effect on the taste of the aerosol-generating articles was observed.

[0088] Made from pulp fibre and contains no filler material, 20g / m 2 was used to produce a further wrapper paper according to the invention, both sides of which were impregnated in a size press with a composition comprising water and polyphosphate (step F.1), so that the wrapper paper then contained 8% polyphosphate relative to the weight of the wrapper paper. The wrapper paper was bonded to a further paper layer by lamination. The additional paper layer had a weight of 24 g / m 2 grammage, 28% filler content relative to the mass of the paper layer, and 75 cm 3 / (cm 2 The wrapper paper also had an air permeability of 1.5 min. kPa. A good flame-retardant effect was observed for this wrapper paper. After the aerosol-generating article was manufactured and used, it was clearly noticeable that discoloration of the wrapper paper was substantially imperceptible due to the additional outer paper layer.

[0089] 30g / m 2 Further wrapper paper according to the present invention was produced using the base paper of Example 1, which contained pulp fibers and bentonite as a filler material in an amount of about 34% based on the mass of the base paper. Both sides of this base paper were impregnated with a composition containing water and polyphosphate in a size press over the entire surface (step F.1), so that the base paper then contained about 5% polyphosphate. Despite the low polyphosphate content, a good flame retardant effect could be observed. The inventors speculate that the high moisture content of the bentonite contributes to the flame retardant effect.

[0090] Aerosol-generating articles were made from this wrapper paper according to the invention and it was found that discoloration of the wrapper paper was less evident due to the lower polyphosphate content.

[0091] The wrapper paper according to the invention is therefore very well suited for use in aerosol-generating articles, with good biodegradability and flame retardant effectiveness, a combination of properties that is superior to comparable wrapper papers of the prior art.

Claims

1. An aerosol-generating article comprising a wrapper paper and an aerosol-generating material, wherein the wrapper paper encases the aerosol-generating material, and wherein during use, the aerosol-generating material is only heated but does not burn; The wrapper paper comprises pulp fibers and one or more polyphosphates, the pulp fibers comprising at least 70% and at most 95% by weight of the wrapper paper, the polyphosphates being present in a concentration of at least 5% and at most 30% by weight of the wrapper paper, and the polyphosphates having the molecular formula M ｎ＋２ P ｎ O ３ｎ＋１ or M ｎ [H ２ P ｎ O ３ｎ＋１ wherein n is at least 2 and at most 100, and M is a monovalent metal or ammonium (NH ４ ＋ ) an aerosol-generating article.

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

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

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

5. 5. The aerosol-generating article according to claim 1, wherein the pulp fibres are sourced from softwood in a proportion of at least 25% and at most 100% by mass of the pulp fibres.

6. 6. An aerosol-generating article according to any one of claims 1 to 5, wherein the proportion of polyphosphate in the wrapper paper is at least 9% and at most 25% by mass of the wrapper paper.

7. The polyphosphate salt has the molecular formula M ｎ＋２ P ｎ O ３ｎ＋１ or M ｎ [H ２ P ｎ O ３ｎ＋１ 7. The aerosol-generating article according to claim 1, wherein the value n in [mathematical formula - see original document] is at least 3 and at most 80.

8. The polyphosphate salt has the molecular formula M ｎ＋２ P ｎ O ３ｎ＋１ or M ｎ [H ２ P ｎ O ３ｎ＋１ 8. The aerosol-generating article according to claim 1, wherein the monovalent metal M is selected from the group consisting of lithium, sodium and potassium.

9. The polyphosphate salt has the molecular formula M ｎ＋２ P ｎ O ３ｎ＋１ or M ｎ [H ２ P ｎ O ３ｎ＋１ 9. The aerosol-generating article according to claim 1, wherein the value of n in formula (II) is at least 15 and at most 30, and the monovalent metal M is sodium.

10. 10. The aerosol-generating article according to any one of claims 1 to 9, wherein the polyphosphate comprises sodium hexametaphosphate.

11. 11. An aerosol-generating article according to any one of claims 1 to 10, wherein the side of the wrapper paper that faces the aerosol-generating material or that faces away from the aerosol-generating material during use contains a higher proportion of polyphosphate than the other side of the wrapper paper.

12. 12. The aerosol-generating article of any one of claims 1 to 11, wherein the polyphosphate is at least substantially uniformly distributed over at least 70%.

13. An aerosol-generating article according to any one of the preceding claims, wherein the wrapper paper is bonded to a further layer of material, in particular by gluing.

14. 14. An aerosol-generating article according to claim 13, wherein the further layer of material is a layer of aluminium foil, plastic foil, foil made from regenerated cellulose or foil made from cellulose hydrate.

15. 14. The aerosol-generating article according to claim 13, wherein the further layer is a paper layer.

16. 16. The aerosol-generating article of claim 15, wherein the paper layer comprises pulp fibers and white filler particles, the white filler particles constituting 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 use.

17. The paper layer has a thickness of at least 5 cm as measured in accordance with ISO 2965:2019. ３ / (cm ２ min kPa) and up to 30,000 cm ３ / (cm ２ and the paper layer has a basis weight of at least 10 g / m ２ and up to 30 g / m ２ 16. The aerosol-generating article according to claim 15,

18. The paper layer has a thickness of at least 30 g / m ２ and up to 100 g / m ２ 16. The aerosol-generating article of claim 15, having a basis weight of

19. 19. The aerosol-generating article of any one of claims 1 to 18, further comprising at least one additional ingredient selected from the group consisting of filler materials, sizing agents, wet strength agents, additives, processing aids, humectants, and flavoring agents.

20. 20. The aerosol-generating article of claim 19, wherein the proportion of the filler material is at least 0% and at most 45% by weight of the wrapper paper.

21. 21. The aerosol-generating article of claim 19 or 20, wherein the filler material is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, kaolin, talcum, bentonite, and mixtures thereof.

22. 22. An aerosol-generating article according to any one of claims 1 to 21, wherein the wrapper paper is coated or impregnated with a material selected from the group consisting of starches 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, hydroxyethyl cellulose and salts thereof; polysaccharides such as alginates; polyvinyl alcohol; polyvinyl acetate; ethylene vinyl acetate; gelatin; gums such as gum arabic, guar gum, locust bean gum or tragacanth gum; or mixtures thereof.

23. 23. An aerosol-generating article according to any one of claims 1 to 22, wherein the wrapper paper has a KIT level, determined according to TAPPI T 559cm-12, of at least 3 and at most 8.

24. The wrapper paper has a thickness of at least 15 g / m ２ and up to 120 g / m ２ 24. The aerosol-generating article of any one of claims 1 to 23, having a basis weight of

25. 25. An aerosol-generating article according to any one of claims 1 to 24, wherein the wrapper paper has a thickness of at least 25 μm and at most 150 μm.

26. 26. An aerosol-generating article according to any preceding claim, wherein the wrapper paper has a longitudinal tensile strength of at least 10 N / 15 mm and at most 100 N / 15 mm.

27. 27. An aerosol-generating article according to any one of the preceding claims, wherein the wrapper paper has a wet tensile strength in the longitudinal direction according to ISO 12625-5:2016 of at least 1 N / 15 mm and at most 10 N / 15 mm.

28. The wrapper paper is at least 0 cm ３ / (cm ２ ・min・kPa) and up to 30 cm ３ / (cm ２ 28. The aerosol-generating article according to any one of claims 1 to 27, having an air permeability according to ISO 2965:2019 of 1.5 .mu.m / min.kPa.

29. 29. An aerosol-generating article according to any one of claims 1 to 28, wherein the wrapper paper has an opacity of at least 40% and at most 90% and / or a brightness of at least 80% and at most 95%.

30. 30. An aerosol-generating article according to any one of claims 1 to 29, wherein one side of the wrapper paper has a higher proportion of polyphosphate than the other side, and the side with the higher proportion of polyphosphate faces the aerosol-generating material or faces away from the aerosol-generating material.

31. 31. An aerosol-generating article according to any one of claims 1 to 30, wherein the aerosol-generating article is an electrically heated aerosol-generating article, the material of which is heated from the inside during use, and the wrapper paper contains polyphosphate in an amount of at least 5% and at most 25% by weight of the wrapper paper.

32. 31. An aerosol-generating article according to any one of claims 1 to 30, wherein the aerosol-generating article is an electrically heated aerosol-generating article, the aerosol-generating material of which is heated from the outside during use, and the wrapper paper contains polyphosphate in an amount of at least 10% and at most 30% by weight of the wrapper paper.

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