Nonwoven airlaid substrate for filter

Abstract

The present disclosure relates to a nonwoven airlaid substrate designed for use in filters for smoking or vaping articles. The technical problem addressed can be that the high variability in density and mass surface of traditional nonwoven airlaid substrates can affect filtration performance. This disclosure provides a solution by offering a substrate composed of 70% to 99% natural fibers and 1% to 30% natural binder, with a thickness ranging from 200 µm to 800 µm and a density of at least 61 mg / cm3. This composition ensures reduced variability, enhanced tensile strength, and environmental sustainability by eliminating cellulose acetate.

Description

DescriptionNONWOVEN AIRLAID SUBSTRATE FOR FILTERTechnical Field

[0001] The present disclosure relates to nonwoven airlaid substrate, specifically to nonwoven airlaid substrate with enhanced variability for industrial applications. The subject of the invention is nonwoven airlaid substrate having a high density and comprising natural fibers and a binder. The nonwoven airlaid substrate can be used for a filter for a smoking or vaping article.Background Art

[0002] Cigarette filters have traditionally included cellulose acetate due to its effective filtration properties. However, recent regulatory changes have prohibited the use of cellulose acetate in cigarette filters. As a result, there is need to identify and develop alternative materials that can meet the new regulatory standards while maintaining the desired filtration performance. Nonwoven materials comprising natural fibers have been identified like possible alternatives.

[0003] A nonwoven airlaid substrate is a type of nonwoven fabric produced by dispersing fibers in an air stream and depositing them onto a moving belt or forming screen. This process results in a web of fibers that can be further bonded together using various methods, such as thermal bonding, chemical bonding, or mechanical bonding. Traditional nonwoven airlaid substrates can exhibit significant variability in terms of mass surface and thickness. This variability can lead to regions within the material that have high density and others with low density, with variations reaching more than 20% around a mean value.

[0004] While such variability may not pose a significant issue for applications like diapers or other absorbent products, it becomes problematic in the filter industry, particularly for filter rods used in cigarettes. In this context, variability can result in some filter rods meeting regulatory standards while others, especially those sourced from low-density regions of the material, fail to comply.Summary

[0005] The invention addresses the need for nonwoven airlaid substrate with improved variability, making them more effective for industrial applications such as filters for smoking article or vaping articles.

[0006] In one aspect, it is proposed a nonwoven airlaid substrate for a filter, whereby the nonwoven airlaid substrate comprises:from 70 % to 99 % of natural fibers by weight of the solids in the material,from 1 % to 30 % of natural binder by weight of the solids in the material, and characterized in thatthe thickness of the nonwoven airlaid substrate ranges from 200 pm to 800 pm, and the density of the nonwoven airlaid substrate is greater or equal to 61 mg / cm3

[0007] In another aspect, it is proposed a filter for a smoking or a vaping article comprising a nonwoven airlaid substrate according to the present disclosure.

[0008] In another aspect, it is proposed a process for producing the filter according to the present disclosure, the process comprising the steps of:forming a rod of nonwoven airlaid substrate from a nonwoven airlaid substrate according to the present disclosure,wrapping the rod with a sheet of plug wrap paper,sealing the sheet of plug wrap paper to obtain a rod of filtering material.

[0009] In still another aspect, it is proposed a process for producing the nonwoven airlaid substrate according to the present disclosure, the process comprising the following steps:producing a web from natural fibers by an airlaid process,introducing a binder into the web.Description of Embodiments

[0010] Other features, details and advantages will be shown in the following detailed description.

[0011] According to a first aspect, the present disclosure concerns a nonwoven airlaid substrate for a filter, whereby the nonwoven airlaid substrate comprises:from 70 % to 99 %, in particular from 80 % to 98 %, very particularly from 85 % to 98 % of natural fibers by weight of the solids in the substrate,from 1 % to 30 %, in particular from 2 % to 20 %, very particularly from 2 % to 15 %, even more particularly from 5 % to 10 % of natural binder by weight of the solids in the substrate, andcharacterized in thatthe thickness of the nonwoven airlaid substrate ranges from 200 pm to 800 pm, for instance around 300 pm, 500 pm, or 700 pm, in particular from 400 pm to 600 pm, more particularly from 510 pm to 560 pm, for instance 520 pm or 550 pm,the density of the nonwoven airlaid substrate is greater or equal to 61 mg / cm3, in particular from 61 mg / cm3to 200 mg / cm3, for instance 67 mg / cm3, 93 mg / cm3, 99 mg / cm3, or 165 mg / cm3, in particular the density is from 65 mg / cm3to 100 mg / cm3and even more particularly from 90 mg / cm3to 100 mg / cm3.

[0012] According to another aspect, the present disclosure concerns a filter comprising the nonwoven airlaid substrate of the disclosure, for a smoking or a vaping article.

[0013] A nonwoven airlaid substrate within the specified ranges can exhibit reduced variability in terms of density and basis weight compared to substrates outside these ranges. This consistency means that samples taken from a same sheet of nonwoven airlaid substrate could have uniform properties, making the substrate potentially more reliable for industrial applications such as filter forsmoking or vaping articles. Additionally, the substrate's design could facilitate crimping, contributing to its structural integrity. The substrate's composition, free from cellulose acetate, may also make it compostable, aligning with environmental sustainability goals.

[0014] Variability, in the context of the present disclosure, can refer to the degree of fluctuation or inconsistency in properties such as basis weight and / or thickness across different sections of the material. High variability can lead to uneven performance and quality, which can be problematic in applications like filters for smoking article or vaping article.

[0015] To measure variability, multiple samples are taken from different areas of the nonwoven material, and the variation in their properties is assessed. Statistical methods, such as calculating the standard deviation or the coefficient of variation, are used to quantify this variability.

[0016] In the development of the nonwoven airlaid substrates according to the present disclosure, efforts were made to reduce the variability. For instance, the 3-sigma variation in basis weight can be reduced from 21 % for a nonwoven airlaid substrate not according to the present disclosure to 14 % for a nonwoven airlaid substrate according to the present disclosure and the 3-sigma variation in thickness can be reduced from 22 % for a nonwoven airlaid substrate not according to the present disclosure to 18 % for a nonwoven airlaid substrate according to the present disclosure.

[0017] When utilized in a filter, the nonwoven airlaid substrate can provide consistent pressure drop results for effective filtration in smoking and vaping applications. The substrate can maintain the visual aspects and hardness of the filter rods. By eliminating cellulose acetate, the filter can become more environmentally friendly without compromising on filtration efficiency or structural durability. These attributes can make the nonwoven airlaid substrate a good choice for modern filter designs that meet both regulatory and consumer demands.

[0018] Additionally, a nonwoven airlaid substrate within these specified ranges exhibits enhanced tensile strength compared to substrates that fall outside these parameters.

[0019] Tensile strength can be defined as the maximum amount of tensile stress that a material can withstand while being stretched or pulled before breaking. It is a property that can indicate the durability and robustness of a material, particularly in applications where the material can be subjected to tension.

[0020] The unit of measurement for tensile strength is typically expressed in terms of force per unit width, such as Newtons per 50 millimeters (N / 50mm).

[0021] To measure tensile strength, a sample of the material is prepared and clamped at both ends in a tensile testing machine following standard WSP 110.4. The machine applies a controlled tensile force to the sample, gradually increasing the load until the material breaks. The force applied at the point of failure is recorded, and the tensile strength is calculated by dividing this force by the initial cross-sectional area of the sample.

[0022] The tensile strength of the nonwoven airlaid substrate can be equal or greater to 10 N / 50mm, in particular the tensile strength is equal or greater to 15 N / 50mm, even more particularly the tensile strength of the nonwoven airlaid substrate ranges from 15 N / 50mm to 25 N / 50mm.

[0023] For the purposes of the present application, "nonwoven airlaid substrate" (also referred to as "non-woven substrate") can relates to a manufactured sheet consisting of a web or ply of directionally or randomly oriented fibers bonded together by friction and / or cohesion and / or adhesion.

[0024] Typically, the density of the nonwoven airlaid substrate is calculated by dividing its basis weight by its thickness. The density should be assessed directly from the airlaid substrate itself, rather than, for instance, when it is packed, such as inside a wrapper to form a filter. Packing the airlaid substrate can lead to an increased density.

[0025] The standard ISO 536:2012 can be used to determine the basis weight of the nonwoven airlaid substrate. The substrate is conditioned for at least 16 hours at23°C and 50 % relative humidity before the measurement.

[0026] The basis weight of the nonwoven airlaid substrate of the filter of the invention can for example be between 30 g / m2and 70 g / m2, in particular between 30 g / m2and 60 g / m2, more particularly between 45 g / m2and 55 g / m2, for instance 50 g / m2.

[0027] To measure the thickness of the nonwoven airlaid substrate, it is possible to use a deadweight micrometer comprising a 25 cm2measuring head with two planar, parallel and circular pressure surfaces. During the measurement, the nonwoven airlaid substrate is placed between the two pressure surfaces for 10 seconds. The pressure exerted between the pressure surfaces during the measurement of the thickness is 0.5 kPa. The substrate is conditioned for at least 16 hours at 23°C and 50% relative humidity before the measurement.

[0028] According to one particular embodiment, the nonwoven airlaid substrate can have a density of between 90 mg / cm3and 100 mg / cm3, and a thickness of between 510 pm and 560 pm.

[0029] For instance, the nonwoven airlaid substrate can have a density of around 93 mg / cm3, and a thickness of around 550 pm.

[0030] For instance, the nonwoven airlaid substrate can have a density of around 99 mg / cm3, and a thickness of around 520 pm.

[0031] The person skilled in the art will know how to adapt the basis weight and the thickness of the nonwoven airlaid substrate in order to achieve the desired density.

[0032] For the purposes of the present application, the term "natural fiber" denotes a fiber of natural origin which has optionally undergone a chemical treatment, a physical treatment, or both, in order to improve the physical characteristics thereof.

[0033] For example, the natural fibers can be chosen from wood fibers, leaf fibers, fruit fibers, seed fibers, bast fibers, stalk fibers, reed fibers, and mixtures thereof, in particular from wood fibers, leaf fibers, seed fibers, bast fibers, and mixtures thereof, more particularly from wood fibers and mixtures thereof. Examples of wood fibers which may be present in the nonwoven airlaid substrate of the filterof the invention can be hardwood pulp, bleached hardwood pulp, softwood pulp, bleached softwood pulp, softwood fluff pulp, lyocell fibers (cellulose fibers which are ground and dissolved in N-methylmorpholine N-oxide monohydrate for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with calibrated length and mass per unit length, which the person skilled in the art can choose depending on their needs), viscose fibers (fibers obtained by dissolving cellulose by means of modification of its hydroxyl groups by carbon disulfide (CS2) and then its precipitation in the presence of sulfuric acid (H2SO4) for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with calibrated length and mass per unit length, which the person skilled in the art can choose depending on their needs), and mixtures thereof, in particular hardwood pulp, softwood pulp, softwood fluff pulp, lyocell fibers, viscose fibers, and mixtures thereof, more particularly softwood pulp, softwood fluff pulp, lyocell fibers, and mixtures thereof.

[0034] For the purposes of the present application, "bast fiber" denotes a plant fiber contained in the bast of the plants.

[0035] As bast fiber, mention may be made of hemp fiber, Indian hemp fiber, jute fiber, kenaf fiber, kudzu fiber, coin vine fiber, flax fiber, okra fiber, nettle fiber, papyrus fiber, ramie fiber, sisal fiber, esparto fiber, and mixtures thereof, in particular hemp fiber, flax fiber, and a mixture thereof, more particularly flax fiber.

[0036] Typically, the bast fibers may have undergone prior treatment. Thus, the bast fibers may be cottonized bast fibers, individualized bast fibers, bast fibers which have undergone retting, bleached bast fibers, and mixtures thereof, in particular cottonized bast fibers, individualized bast fibers and a mixture thereof.

[0037] For the purposes of the present application, "seed fiber" denotes a fiber obtained from seeds of a plant. Examples of seed fibers can be cotton fiber, kapok fiber, luffa fiber, milkweed fiber, and mixtures thereof, in particular kapok fiber.

[0038] According to one particular embodiment, the natural fibers are chosen from softwood pulp, softwood fluff pulp, in particular softwood fluff pulp.

[0039] According to the invention, the natural fibers have a length of between 1 mm and 10 mm, in particular between 1.5 mm and 8 mm, very particularly between 2 mm and 5 mm.

[0040] An airlaid process can be suitable for these sizes of natural fibers. Thus, the nonwoven airlaid substrate of the filter of the invention can be obtained by an airlaid process.

[0041] The length of the natural fibers can be measured by microscopic measurement using a projection microscope by means of the necessary magnification.

[0042] The natural fibers may also be cut so as to have a length within the ranges mentioned above. Conventional cutting techniques which can be used are guillotine cutting of natural fibers, grinding of the natural fibers with or without a system for removing excessively short and excessively long fibers of air cyclone or screen type.

[0043] In preferred embodiments, reduced variability in the airlaid substrate is achieved by jointly controlling short fiber length, sheet density / thickness, and tensile strength. Using natural fibers with a length between 1 mm and 10 mm, typical of airlaid processes, promotes homogeneous fibers distribution and uniform bonding, which can reduce localised voids and / or thickness fluctuations across the web. When combined with a narrowed sheet density window, for example between 65 mg / cm3and 100 mg / cm3and more particularly from 90 mg / cm3to 100 mg / cm3, and a sheet thickness in the range between 400 pm and 600 pm and more particularly from 510 pm to 560 pm, the airlaid substrate can exhibits a low variability that can advantageously translate into consistent rod formation and pressure drop during plug-making. Furthermore, setting a minimum tensile strength threshold, for example equal or more than 10 N / 50 mm, more particularly the tensile strength of the nonwoven airlaid substrate ranges from 15 N / 50mm to 25 N / 50mm, improves runnability on high-speed lines by resisting web breaks and deformation, thereby maintaining dimensional integrity and further limiting variability in the finished filter components.

[0044] For the purposes of the present application, "natural binder" denotes a compound having properties enabling consolidation of the nonwoven airlaid substrate. Advantageously, water-soluble binders will be chosen. Water-soluble is understood to refer to the ability of the binder to dissolve in water at a temperature and with stirring which are controlled, to form a homogeneous solution at ambient temperature and not a suspension. After drying of the substrate with this binder, the substrate is dispersible since the binder is soluble in water. Advantageously, the nonwoven airlaid substrate is dispersible in water at ambient temperature in less than 60 s.

[0045] For example, the binder can be chosen from a polysaccharide, a cellulose derivative, a polyvinyl alcohol (PVOH) and mixtures thereof.

[0046] The polysaccharide which can be used as binder can be a polysaccharide or a polysaccharide derivative. For example, starch, dextrin, gum arabic, pectin and mixtures thereof can be used as binder, in particular starch.

[0047] For example, the cellulose derivative can be chosen from ethyl cellulose, methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, an alkali metal salt of carboxymethyl cellulose, and mixtures thereof, in particular carboxymethyl cellulose. A carboxymethyl cellulose with a degree of substitution of greaterthan 0.4 is particularly advantageous. Typically, the degree of substitution will be between 0.6-0.9.

[0048] As alkali metal of the carboxymethyl cellulose salt, mention may be made of potassium, sodium, and magnesium.

[0049] Polyvinyl alcohol may also be used as binder, in particular polyvinyl alcohol with a degree of hydrolysis of less than 99 %, less than 95 %, or less than 90 %.

[0050] According to a very particular embodiment, the nonwoven airlaid substrate comprises softwood fluff pulp and a binder chosen from starch, carboxymethyl cellulose or polyvinyl alcohol, in which the softwood fluff pulp represents between 85 % and 95 % by weight of solids of said nonwoven airlaid substrate and the binder represents between 5 % and 15 %, preferably between5 % and 10 % by weight of solids of said nonwoven airlaid substrate; and has a density of between 65 mg / cm3to 100 mg / cm3.

[0051] The nonwoven airlaid substrate of this very particular embodiment can be obtained by an airlaid process.

[0052] The filter of the invention may be a filter for a smoking orvaping article comprising a nonwoven airlaid substrate of the invention as defined above.

[0053] For the purposes of the present application, "smoking article" denotes an article comprising tobacco and / or any other plant intended to be smoked. For example, the smoking article may be a machine-manufactured cigarette, a roll-your-own cigarette or a make-your-own cigarette.

[0054] Typically, the filter for a smoking article has a right circular cylindrical shape and comprises an outer envelope of plug wrap paper for a smoking article, in particular for a cigarette, and the nonwoven airlaid substrate of the filter of the invention as defined above located within the outer envelope.

[0055] For the purposes of the present application, "vaping article" denotes an article comprising tobacco and / or any other plant intended to be vaped, which is intended to be inserted into a device which heats the tobacco and / or the plant without burning said tobacco / plant and which enables delivery of an aerosol to a user. For example, the vaping article can be a tobacco stick.

[0056] Typically, the filter for a vaping article has a right circular cylindrical shape and comprises an outer envelope of plug wrap paper for a vaping article, in particular for a tobacco stick, and the nonwoven airlaid substrate of the filter of the invention as defined above located within the outer envelope.

[0057] The filter of the invention can have a density of between 150 mg / cm3and 250 mg / cm3, for instance 170 mg / cm3or 215 mg / cm3.

[0058] Typically, the density of the filter is measured after manufacture of the filters, by dividing the mass of the filter by its volume. For a filter having a right circular cylindrical shape, the volume of the filter (Vfiiter) is calculated by the following formula: Vfiiter = TT*L*r2, in which r denotes the radius of the filter and L denotes the length of the filter.

[0059] According to another aspect, the present invention also relates to a smoking article comprising a filter as defined above.

[0060] According to another aspect, the present invention also relates to a vaping article comprising a filter as defined above.

[0061] The present invention also relates to the use of a nonwoven airlaid substrate as defined above in a filter, in particular a filter for a smoking article or a filter for a vaping article.

[0062] The present disclosure also relates to a process for producing the filter of the invention comprising a nonwoven airlaid substrate, said process comprising the following steps:a) forming a rod of nonwoven airlaid substrate from a nonwoven airlaid substrate,b) wrapping the rod of nonwoven airlaid substrate with a sheet of plug wrap paper, optionally c) sealing, for example with an adhesive line, the sheet of plug wrap paper to obtain a rod of filtering material,optionally d) cutting the rod of filtering material to produce the filter,wherein the nonwoven airlaid substrate is as defined above or is obtained by a process comprising the following steps:i) producing a web from natural fibers by an airlaid process,ii) introducing a natural binder into the web, andiii) drying the web resulting from step ii) to obtain the nonwoven airlaid substrate.

[0063] The nonwoven airlaid substrate, the natural fibers and the binder are as described above in relation to the nonwoven airlaid substrate.

[0064] The nonwoven airlaid substrate of the filter of the invention can therefore be obtained by an airlaid process.

[0065] The airlaid process and the drylaid process are two different conventional routes known to the person skilled in the art to produce a web. The person skilled in the art will know how to adapt the parameters of the airlaid process to produce the nonwoven airlaid substrate of the filter of the invention.

[0066] The process of the invention can comprise, before production step i), a step i1) of cutting the natural fibers to obtain natural fibers having a length within the ranges mentioned above.

[0067] Cutting step i1) can be carried out by conventional techniques such as guillotine cutting, grinding of the natural fibers with or without a system for removing excessively short and excessively long fibers of air cyclone or screen type.

[0068] During introduction step ii), an aqueous dispersion of the binder can be introduced into the web. This introduction may for example be carried out by impregnation, such as impregnation with a size press, by spraying, such as spraying using a spray, by surface application, such as surface application by coating or by printing, in particular by spraying using a spray. Advantageously, the spraying will be performed on both faces of the web.

[0069] The aqueous dispersion of the binder can be obtained by any technique known to the person skilled in the art. The person skilled in the art will know how to adapt the concentration of binder in the aqueous dispersion to obtain the desired content of binder in the nonwoven airlaid substrate of the invention.

[0070] Drying step iii) can, for example, be carried out by a drying device, such as a tunnel through which air passes or an infrared ramp.

[0071] This drying step iii) can be carried out at a temperature of between 75°C and 220°C, in particular between 90°C and 200°C, more particularly between 100°C and 190°C.

[0072] A temperature within these ranges advantageously makes it possible to minimize the duration of this drying step iii) while at the same time minimizing the deterioration of the natural fibers of the nonwoven airlaid substrate.

[0073] Advantageously, the combination of the introduction step ii) and of the drying step iii) makes it possible to improve the cohesion of the natural fibers and hence to consolidate the structure of the nonwoven airlaid substrate of the invention.

[0074] The natural fibers used in production step i) can be a mixture of natural fibers. This mixture of natural fibers can be obtained before production step i).

[0075] The process may also comprise, between production step i) and introduction step ii), a step ii1) of compacting the web to obtain a compacted web, this compacted web then undergoing introduction step ii).

[0076] This compacting step ii1) can make it possible to reduce the thickness of the web in order to control the density of the nonwoven airlaid substrate.

[0077] According to a very particular embodiment, the process can comprise the following steps:i) producing a web from a softwood fluff pulp by an airlaid process,ii) introducing a binder chosen from starch, carboxymethyl cellulose or polyvinyl alcohol into the web by spraying an aqueous dispersion of the binder, andiii) drying the web resulting from step ii) to obtain a nonwoven airlaid substrate which can have a density greater or equal to 61 mg / cm3and in which the softwood fluff pulp can represent between 85% and 95% by weight of solids of said nonwoven airlaid substrate and the starch can represent between 5% and 15% by weight of solids of said nonwoven airlaid substrate.

[0078] The nonwoven airlaid substrate of the filter of the invention may not be shaped in the filter. In particular, the nonwoven airlaid substrate of the filter of the invention may not be folded in a V shape and / or crimped in the filter. This can be advantageous since it makes it possible to produce a filter without a step of shaping the substrate, and hence to simplify the production of the filter.

[0079] Optionally, the nonwoven airlaid substrate obtained at step iii) may be calendered and / or crimped.

[0080] Crimping can be a challenging process due to the numerous parameters involved, making it far from a routine task. Factors such as the substrate's thickness, density, and fiber composition all can play roles in determining the success of crimping. Variations in these parameters can lead to inconsistent results.

[0081] After step iii) and before step a), the nonwoven airlaid substrate may be packed as bobbin, as roll by a spooling process or in paperboard by a festooning process.Examples

[0082] Nonwoven airlaid substrates have been produced in accordance with the method described in the present disclosure.

[0083] These substrates were manufactured with varying characteristics, which are detailed in Table 1. A comparative example was also created, featuring characteristics outside the specified ranges of this disclosure.

[0084] The nonwoven airlaid substrates developed according to the present disclosure demonstrate improved consistency in terms of basis weight and density. This means that the variability is reduced for the nonwoven airlaid substrates produced in accordance with this disclosure, compared to the comparative example not adhe ring to these specified parameters.

[0085] This reduction in variability ensures more uniform properties across different samples, enhancing the material's reliability and s uitability for industrial applications such as filter for smokingor vaping articles.

[0086] Additionally, the substrates from Exampl e s 1, 2, 3, and 4, which adhere to the specifiedranges, show enhanced resistance in terms of tensile strength.

[0087] [Table 1]

Claims

CLAIMS

1. Nonwoven airlaid substrate for a filter, whereby the nonwoven airlaid substrate comprises:from 70 % to 99 % of natural fibers by weight of the solids in the material,from 1 % and 30 % of natural binder by weight of the solids in the material,the thickness of the nonwoven airlaid substrate ranges from 200 pm to 800 pm, and the density of the nonwoven airlaid substrate is greater or equal to 61 mg / cm3.

2. The nonwoven airlaid substrate according to claim 1 , wherein the natural fibers are chosen from wood fibers, leaf fibers, fruit fibers, seed fibers, bast fibers, stalk fibers, reed fibers, and mixtures thereof.

3. The nonwoven airlaid substrate according to claim 1 or claim 2, wherein the natural fibers are wood fibers chosen from hardwood pulp, bleached hardwood pulp, softwood pulp, bleached softwood pulp, softwood fluff pulp, lyocell fibers, viscose fibers, and mixtures thereof.

4. The nonwoven airlaid substrate according to any one of claims 1 to 3, wherein the length of the natural fibers is between 1 mm and 10 mm.

5. The nonwoven airlaid substrate according to any one of claims 1 to 4, wherein the natural binder is a water-soluble binder.

6. The nonwoven airlaid substrate according to any one of claims 1 to 5, wherein the natural binder is chosen from a polysaccharide, a cellulose derivative, a polyvinyl alcohol and mixtures thereof.

7. The nonwoven airlaid substrate according to any one of claims 1 to 6, wherein the nonwoven airlaid substrate has a basis weight ranging from 40 to 60 g / m2.

8. The nonwoven airlaid substrate according to any one of claims 1 to 7, wherein the tensile strength of said nonwoven airlaid substrate is equal or greater to 10 N / 50mm.

9. A filter for a smoking or a vaping article comprising a nonwoven airlaid substrate according to any one of claims 1 to 8.

10. A process for producing the filter according to claim 9, the process comprising the steps of:forming a rod of a nonwoven airlaid substrate from a nonwoven airlaid substrate according to any one of claims 1 to 8,wrapping the rod with a sheet of plug wrap paper,sealing the sheet of plug wrap paper to obtain a rod of filtering material.

11. A process for producing the nonwoven airlaid substrate according to any one of claims 1 to 8, the process comprising the following steps:producing a web from natural fibers by an airlaid process,introducing a natural binder into the web.

Images