Nonwoven substrate comprising natural fibers and a binder

Abstract

The present invention relates to a nonwoven substrate comprising natural fibers and a binder. In particular, this nonwoven substrate can be used as filter media in a filter for a smoking or vaping article.

Description

DescriptionTitle: Nonwoven substrate comprising natural fibers and a binderTechnical field

[0001] A subject of the invention is a filter comprising, as filter media, a nonwoven substrate comprising natural fibers and a binder. In particular, this filter can be used as filter for a smoking or vaping article.Prior art

[0002] A smoking or a vaping article commonly comprises a filter having a right circular cylindrical shape. A common filter comprises at least two parts: one filter media and one plug wrap paper. The plug wrap paper is the outer envelope of the filter, and the filter media is located within this outer envelope. The filter makes it possible to prevent the user from inhaling tobacco particles and allows retention of harmful particulate substances contained in the smoke or the aerosol produced by the smoking or vaping article, such as tar.

[0003] Filter media of a smoking or vaping article is generally made from cellulose acetate tow. Cellulose acetate filters are known to be a good compromise between production price and customer’s experience. In particular, filters comprising filter media made with cellulose acetate tow exhibit good hardness, good nicotine retention and satisfactory taste.

[0004] The huge environmental impact caused by waste of tobacco products with filters containing cellulose acetate, directly discarded into the environment, needs to be reduced. Directive (EU) 2019 / 904 of the European parliament and of the council of 5 June 2019 on the reduction of the impact of certain plastic products on the environment has been voted to tackle plastic pollution and marine litter. Specific rules and targets apply to certain areas, including tobacco products filters made of plastic.

[0005] For this reason, plenty of research has been carried out to find new filter media alternative that comply with the aforementioned European Directive as forexample filter media made of nonwoven substrate. As nonwoven substrates are made with non-chemically modified cellulose, filters comprising these substrates have lower environmental impact.

[0006] It has been described in PCT / EP2023 / 086807 filters comprising nonwoven substrate comprising natural polysaccharides as binder. Those filters exhibit advantages as they degrade very rapidly in the environment in comparison to cellulose acetate filters.

[0007] The inventors noticed that insufficient mechanical properties of nonwoven substrate may lead, during the manufacturing of filters comprising said nonwoven substrate, to the generation of dust and reduction of yield resulting from the frequent breaking of the nonwoven substrate. The mechanical properties of the nonwoven substrate described in PCT / EP2023 / 086807 are quite satisfactory but can still be optimized to overcome the above-mentioned problems during the manufacturing of filters comprising said nonwoven substrate.Technical problem

[0008] There is therefore a need for a filter comprising a nonwoven substrate that exhibits optimized mechanical properties.

[0009] It is thus to the credit of the inventors to have found that it was possible to meet this need by means of a nonwoven substrate comprising natural fibers and a binder being a mixture of a water-soluble binder and a latex.Summary

[0010] It is proposed a filter comprising a nonwoven substrate as filter media, said nonwoven comprising natural fibers and a binder, wherein the binder is a mixture of a water-soluble binder and a latex.

[0011] Advantageously, the filter of the present invention exhibits higher elongation in comparison to a filter comprising a nonwoven substrate comprising only a water- soluble binder.

[0012] The higher elongation of the nonwoven substrate of the filter of the present invention ensures that said nonwoven substrate can withstand the stresses and strains encountered during the manufacturing of said nonwoven substrate, during the festooning of the nonwoven substrate and during the manufacturing process of filters comprising the nonwoven substrate. In other words, this higher elongation of the nonwoven substrate improves the yield of filters manufacturing.

[0013] Moreover, the higher elongation of the nonwoven substrate of the filter of the present invention advantageously helps to maintain the overall structural integrity of the filter of the present invention, preventing it from tearing or breaking apart during handling or when subjected to external forces. This higher elongation of the nonwoven substrate improves the user experience.

[0014] Without wishing to be bound by any theory, the inventors are of the opinion that the latex enables the elongation of the nonwoven substrate of the present invention to be higher than the elongation of a nonwoven substrate comprising only a natural binder.

[0015] In comparison to a filter comprising a nonwoven substrate comprising only a latex, the filter of the present invention also exhibits lower air permeability and faster dispersibility in water.

[0016] The lower air permeability of the filter of the present invention is particularly advantageous since it increases the filtration efficiency.

[0017] The faster dispersibility in water of the filter of the present invention are particularly advantageous as the environmental impact of said filter is very small.

[0018] The lower air permeability and the faster dispersibility in water of the filter of the present invention are unexpected since it is known that the filtration efficiency of a filter comprising a nonwoven substrate comprising only a latex is low, and that latex does not disperse rapidly in water. For instance, a nonwoven comprising only latex as binder can resist up to 20 washing cycles.

[0019] It results from the above that, by adding latex to increase the elongation of the nonwoven substrate disclosed in PCT / EP2023 / 086807 comprising a water- soluble binder, the inventors arrived at the nonwoven substrate of the filter of thepresent invention that, unexpectedly: capitalizes on the advantages of each type of binder (rapid dispersibility in water and high filtration efficiency with the water-soluble binder, high elongation with the latex), while mitigating their disadvantages (low elongation due to the high breakability with the water-soluble binder, slow dispersibility in water and poor filtration efficiency with the latex), so that the properties of the nonwoven substrate of the filter of the invention are balanced and optimized.

[0020] Moreover, the filter of the present invention has properties fulfilling the needs of the user of smoking or vaping article, such as filter hardness, no harsh taste of the smoke / aerosol, and low or no formaldehyde content in smoke. These results are also unexpected since the inventors noticed that filters comprising a nonwoven substrate comprising only latex as binder also present low hardness, produce a smoke / aerosol having a harsh taste and emit smoke that may contain formaldehyde.

[0021] Advantageously, the filter of the invention is adapted to be used as a filter for a smoking or vaping article.

[0022] According to another aspect, a smoking or a vaping article comprising the filter of the present invention is proposed.

[0023] According to another aspect, a nonwoven substrate is proposed, said nonwoven substrate comprising natural fibers and a binder, wherein the binder is a mixture of a water-soluble binder and a latex.

[0024] According to another aspect, a process is proposed for producing the filter, in particular a filter for a smoking or vaping article, of the present invention as defined above, said process comprising the following steps: a) forming a rod of nonwoven substrate from a nonwoven substrate, b) wrapping the rod of nonwoven substrate with a sheet of plug wrap paper, c) depositing an adhesive line, joining the sheet of plug wrap paper to obtain a rod of filtering material, d) cutting the rod of filtering material to produce the filter.

[0025] According to another aspect, a process is proposed for producing the nonwoven substrate of the invention comprising the following steps: i) producing a web from natural fibers by an airlaid process or a drylaid process, in particular an airlaid process, ii) introducing the binder into the web, and iii) drying the web resulting from step ii) to obtain the nonwoven substrate.Detailed description of the invention

[0026] It is proposed a filter comprising a nonwoven substrate as filter media, said nonwoven substrate comprising natural fibers and a binder, wherein the binder is a mixture of a water-soluble binder and a latex.

[0027] For the purposes of the present application, “filter” denotes a component that is designed to reduce the amounts of particles and harmful substances, such as tar, that are inhaled by the user of smoking or vaping article. The filter is thus intended to trap and retain particulate matter while allowing the smoke or the aerosol produced by the smoking or vaping article to pass through for inhalation. Typically, the filter has a right circular cylindrical shape and comprises an outer envelope of plug wrap paper and a nonwoven substrate, as filter media, located within this outer envelope.

[0028] For the purposes of the present application, "nonwoven substrate" (also referred to as "non-woven substrate") denotes 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.

[0029] For the purposes of the present application, "binder" denotes a compound having properties enabling chemical consolidation of the nonwoven substrate.

[0030] For the purposes of the present application, “water-soluble binder” refers to a binder having the ability 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. A water-soluble binder is not a water-dispersible binder since a water-dispersible binder cannot be dissolved in water.

[0031] For example, the water-soluble binder can be chosen from a polysaccharide, a cellulose derivative, a polyvinyl alcohol (PVOH) and mixtures thereof, in particular from a polysaccharide, a cellulose derivative and mixtures thereof, more particularly a polysaccharide.

[0032] Advantageously, the polysaccharide and the cellulose derivative are natural binder, i.e. binder that is derived from natural sources.

[0033] The polysaccharide which can be used as water-soluble binder can be a polysaccharide or a polysaccharide derivative. For example, starch, pectin, carrageenan, chitosan, pullulan, guar gum, xanthan gum, dextrin, gum arabic, and mixtures thereof are polysaccharide that can be used as water-soluble binder, in particular starch, pectin or mixtures thereof, more particularly starch.

[0034] 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 greater than 0.4 is particularly advantageous. Typically, the degree of substitution will be between 0.6-0.9.

[0035] As alkali metal of the carboxymethyl cellulose salt, mention may be made of potassium, sodium, and magnesium.

[0036] 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%.

[0037] According to a particular embodiment, the water-soluble binder is starch.

[0038] For the purposes of the present application, “latex” refers to a binder resulting from an emulsion of polymer microparticles in water. The polymer microparticles are present as such in the nonwoven substrate of the present invention.

[0039] Typically, the latex may have a glass transition temperature (Tg) from -20°C to 45°C, in particular -15°C to 36°C, more particularly from -10°C to 20°C.

[0040] Typically, the latex can be chosen from copolymers and polymers comprising ethylene, vinyl acetate, butadiene, styrene, vinyl chloride, acrylic esters, urethanes,and mixtures thereof, in particular from copolymers and polymers comprising ethylene, vinyl acetate, more particularly from copolymers of ethylene and vinyl acetate.

[0041] According to one particular embodiment, the latex has a glass transition temperature from -10°C to 20°C and is a copolymer of ethylene and vinyl acetate.

[0042] The copolymer of ethylene and vinyl acetate is also known as ethylene-vinyl acetate (EVA) and poly(ethylene-vinyl acetate) (PEVA).

[0043] According to one particular embodiment, the latex is hydrophilic.

[0044] For the purposes of the present application, the term "natural fiber" denotes a fiber of natural origin.

[0045] 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, bast fibers and mixtures thereof.

[0046] Examples of wood fibers which may be present in the nonwoven substrate of the filter of the invention can be hardwood pulp, softwood pulp, softwood fluff pulp, bleached hardwood pulp, bleached softwood pulp, bleached 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.

[0047] For the purposes of the present application, "bast fiber" denotes a plant fiber contained in the bast of the plants.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] According to one particular embodiment, the natural fibers are chosen from softwood pulp, softwood fluff pulp, flax fiber, lyocell fiber and mixtures thereof, in particular softwood fluff pulp, flax fiber, lyocell fiber and mixtures thereof, more particularly softwood fluff pulp.

[0052] The natural fibers may have a length of from 1 mm to 10 mm, in particular from 1 .5 mm to 8 mm, very particularly from 2 mm to 5 mm.

[0053] An airlaid process is particularly suitable for these sizes of natural fibers. Thus, the nonwoven substrate of the invention can be obtained by an airlaid process.

[0054] The natural fibers may have a length of from 10 mm to 150 mm, in particular from 15 mm to 100 mm, very particularly from 20 mm to 60 mm.

[0055] A dry laid process is particularly suitable for these sizes of natural fibers. Thus, the nonwoven substrate of the invention can be obtained by a dry laid process.

[0056] The length of the natural fibers can be measured by microscopic measurement using a projection microscope by means of the necessary magnification.

[0057] 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.

[0058] The binder may represent from 5% to 30% by weight of solid of the nonwoven substrate of the present invention, in particular from 8% to 25%, more particularly from 10% to 20%. Independently from the content of the binder or additionally to the content of the binder, the natural fibers may represent from 70% to 95% by weight of solid of the nonwoven substrate of the present invention, in particular from 75% to 92%, more particularly from 80% to 90%.

[0059] The mass ratio of binder: natural fibers in the nonwoven substrate of the present invention may be from 1 :2 to 1 :19, in particular from 1 :3 to 1 :12, more particularly from 1 :4 to 1 :8.

[0060] A content of binder and natural fibers in the above ranges, a ratio in the above ranges, or their combination allows for the production of a nonwoven substrate that effectively addresses environmental concerns without compromising the performance of the filters comprising said nonwoven substrate.

[0061] The water-soluble binder may represent from 7% to 97% by weight of solid of the binder, in particular from 12% to 80%, more particularly from 25% to 75%. Independently from the content of the water-soluble binder or additionally to the content of the water-soluble binder, the latex may represent 3% to 93% by weight of solid of the binder, in particular from 20% to 88%, more particularly from 25% to 75%.

[0062] According to one embodiment, the water-soluble binder represents from 50% to 70% by weight of solid of the binder and the latex represents from 30% to 50% by weight of solid of the binder.

[0063] The mass ratio of water-soluble binder: latex in the binder may be from 1 :0.03 to 1 :13, in particular from 1 :0.25 to 1 :7, more particularly from 1 :0.3 to 1 :3.

[0064] Advantageously, such content of water-soluble binder and latex in the binder, such mass ratio of water-soluble binder: latex in the binder, or their combination:- optimizes the mechanical properties of the nonwoven substrate of the present invention while ensuring the more rapid dispersibility in water of the nonwoven substrate of the present invention, and- optimizes the filter properties and performance (hardness, smoke or aerosol retention and composition, sensory properties) of the filter comprising the nonwoven substrate of the invention.

[0065] For instance, the basis weight of the nonwoven substrate may be of from 20 g.rrr2to 80 g.rrr2, in particular of from 30 g.rrr2to 70 g.rrr2, more particularly of from 40 g.rrr2to 60 g.rrr2

[0066] The standard ISO 536:2012 can be used to determine the basis weight of the nonwoven substrate. The nonwoven substrate can be conditioned for at least 30 min at 23°C and 50% humidity before the measurement.

[0067] The thickness of the nonwoven substrate may be of from 500 pm to 1500 pm, in particular of from 750 pm to 1250 pm, more particularly of from 900 pm to 1100 pm.

[0068] To measure the thickness of the nonwoven substrate, it is possible to use a dead-weight micrometer comprising a 25 cm2measuring head with two planar, parallel and circular pressure surfaces. During the measurement, the nonwoven 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 1 hour at 23°C and 50% humidity before the measurement. For each sample, ten measurements were made with a Micrometer for paper, such as Noviprofibre (N1107P), and the thickness indicated above is the average value.

[0069] The air permeability of the nonwoven substrate may be of from 2500 l / m2 / sec to 3800 l / m2 / sec, in particular of from 3000 l / m2 / sec to 3800 l / m2 / sec, more particularly of from 3200 l / m2 / sec to 3500 l / m2 / sec, even more particularly of from 3300 l / m2 / sec to 3350 l / m2 / sec.

[0070] Air permeability in these ranges is adapted to the use of the nonwoven substrate into filter, in particular into a filter for a smoking or vaping article.

[0071] The air permeability may be determined using an Air permeability tester such as “FX3300 Lab Air IV”. During the measurements, the tested web is placed under the measurement head, and we measured the air flow passing through the web at pressure drop of 200 Pa over the area of 20 cm2. The permeability is measured in [l / m2 / sec]. For each sample, ten measurements were made, and the air permeability indicated above is the average value.

[0072] According to one particular embodiment, the nonwoven substrate of the filter of the invention comprises natural fibers being softwood fluff pulp, and a binder being a mixture of a water-soluble binder being starch, a latex having a glass transition temperature from -10°C to 20°C and being a copolymer of ethylene and vinyl acetate.

[0073] According to one particular embodiment, the nonwoven substrate of the filter of the invention comprises natural fibers being softwood fluff pulp, and a binder being a mixture of a water-soluble binder being starch, a latex having a glass transition temperature from -10°C to 20°C and being a copolymer of ethylene and vinyl acetate, wherein the binder represents from 10% to 20% by weight of solid of the nonwoven substrate, the natural fibers represent from 80% to 90% by weight of solid of the nonwoven substrate, and the water-soluble binder represents from 50% to 70% by weight of solid of the binder and the latex represents from 30% to 50% by weight of solid of the binder.

[0074] The nonwoven substrate of the filter of the invention can be shaped; in particular, it can be crimped, embossed, folded, compressed or combinations thereof. This shaping can make it possible to modify the properties of the nonwoven substrate and therefore the properties of the filter of the invention. For example, through crimping, it is possible, without changing the weight of the filter, to modifythe density of the nonwoven substrate so as to modify the pressure drop of the filter of the invention, thereby modifying also the pressure drop of a smoking article or vaping article comprising the filter.

[0075] The filter of the present invention may be a filter for a smoking or vaping article.

[0076] 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.

[0077] 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 substrate of the filter of the invention as defined above located within the outer envelope.

[0078] 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.

[0079] 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 substrate of the filter of the invention as defined above located within the outer envelope.

[0080] According to another aspect, the present invention also relates to a smoking article comprising a filter comprising a nonwoven substrate as defined above.

[0081] According to another aspect, the present invention also relates to a vaping article comprising a filter comprising a nonwoven substrate as defined above.

[0082] According to another aspect, the present invention relates to a nonwoven substrate. This nonwoven substrate is as defined above in relation with the filter of the present invention.

[0083] The present invention also relates to a process for producing the filter, in particular a filter for a smoking or vaping article, of the present invention as defined above, said process comprising the following steps: a) forming a rod of nonwoven substrate from a nonwoven substrate, b) wrapping the rod of nonwoven substrate with a sheet of plug wrap paper, c) depositing an adhesive line, joining the sheet of plug wrap paper to obtain a rod of filtering material, d) cutting the rod of filtering material to produce the filter.

[0084] The nonwoven substrate is as described above in relation to the filter of the present invention.

[0085] This process is advantageously easy to implement since all the steps a) to d) are well-known by the skilled person. Accordingly, the skilled person skilled will easily know how to adapt the parameters of said steps to produce the filter.

[0086] The nonwoven substrate used in step a) may be shaped. Therefore, the process may comprise, before step a), a step of shaping the nonwoven substrate by crimping, embossing, folding, compression, or combinations thereof, in particular by crimping.

[0087] The present invention also relates to a process for producing the nonwoven substrate as defined above comprising the following steps: i) producing a web from natural fibers by an airlaid process or a drylaid process, in particular an airlaid process, ii) introducing the binder into the web, and iii) drying the web resulting from step ii) to obtain the nonwoven substrate.

[0088] The nonwoven substrate, the natural fibers and the binder of the process for producing the filter are as described above in relation to the filter and the nonwoven of the present invention.

[0089] 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 and the drylaid process to produce the nonwoven substrate of the invention.

[0090] During the step ii), an aqueous dispersion of the binder is 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. Advantageously, the spraying will be performed on both faces of the web.

[0091] 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 substrate of the invention.

[0092] 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.

[0093] This drying step iii) can be carried out at a temperature of from 75°C to 220°C, in particular from 90°C to 220°C, more particularly from 180°C to 210°C. 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 substrate, thus optimizing the process of the invention.

[0094] 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 substrate of the invention.

[0095] 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).

[0096] 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.

[0097] 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.

[0098] 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).

[0099] This compacting step ii1 ) can make it possible to reduce the thickness of the web in order to control the density of the nonwoven substrate.

[0100] Optionally, the nonwoven substrate obtained at step iii) may be shaped, in particular by crimping, embossing, folding, compression, or combinations thereof, more particularly by crimping.

[0101] Optionally, the nonwoven substrate obtained at step iii) may be calendered.

[0102] The nonwoven substrate obtained at step iii) may be involved in step a) of the process for producing the filter of the present invention.

[0103] After step iii), the nonwoven substrate may be packed as bobbin, as roll by a spooling process, or as festooned bale.

[0104] Advantageously, such packages are adapted to the easy transport of the packed nonwoven substrate to the location wherein the process for producing the filter is performed of the present invention.Examples

[0105] Example 1 : Manufacture of the nonwoven substrate

[0106] Six nonwoven substrates were manufactured by the following process:Natural fibers were defibrated into individual fibers and deposited on a forming fabric aerodynamically to obtain a web by an airlaid process. A solution comprising a binder was sprayed on both sides of the web. The sprayed web was then dried by hot air oven at a temperature of 180°C to manufacture the nonwoven substrate.

[0107] For each of the six nonwoven substrates, the type and amount of natural fibers and binder are presented in Table 1 below.

[0108] Table 1

[0109] Example 2: Characterization of the nonwoven substrates

[0110] The properties of the six nonwoven substrates manufactured in Example 1 are determined and indicated in Table 2 below.

[0111] The values indicated in Table 2 are an average of 10 values determined independently.

[0112] The basis weight, the thickness and the air permeability are determined using the methods described above.

[0113] The elongation MD measurements were performed on the substrates according to ISO 1924-2:2008 method, adapted to be performed with 30 mm width specimens at 10 mm / min elongation gradient (speed of jaw separation). The results of elongation MD measurements are presented in Table 2 below.

[0114] To determine the water dispersibility, each substrate is placed in 100 ml of tap water at 22°C stirred at 60 rpm during 30 seconds every 4 hours to check its dispersibility in water. The results of water dispersibility are presented in Table 2 below.

[0115] By comparing the properties of nonwoven substrates 1 , 4, 5 and 6 (according to the invention) to the properties of the nonwoven substrates 2 and 3 (not according to the invention), it is demonstrated that using a mixture of water-soluble binder and latex enables to capitalize on the advantages of the latex and the starch, i.e. improving the elongation of the nonwoven substrate 3 comprising only starch as a binder, reducing the air permeability of the nonwoven substrate 2 comprising only latex as a binder, accelerating the water dispersibility of the nonwoven substrate 2 comprising only latex as a binder.

[0116] The air permeability and elongation of the nonwoven substrates 1 , 4, 5 and 6 are suitable for a use in a filter, in particular a filter for a smoking or a vaping article.0117] Table 2

Claims

Claims

1. A filter comprising a nonwoven substrate as filter media, said nonwoven substrate comprising natural fibers and a binder, wherein the binder is a mixture of a water-soluble binder and a latex.

2. The filter according to claim 1 , wherein the binder represents from 5% to 30% by weight of solid of said nonwoven substrate, and the natural fibers represent from 70% to 95% by weight of solid of said nonwoven substrate.

3. The filter according to claim 1 or claim 2, wherein the water-soluble binder represents from 7% to 97% by weight of solid of the binder, and the latex represents 3% to 93% by weight of solid of the binder.

4. The filter according to any one of claim 1 to 3, wherein the mass ratio of water-soluble binder: latex in the binder is from 1 :0.03 to 1 :13.

5. The filter according to any one of claim 1 to 4, wherein the water-soluble binder is chosen from a polysaccharide, a cellulose derivative, a polyvinyl alcohol (PVOH) and mixtures thereof.

6. The filter according to any one of claim 1 to 5, wherein the latex is chosen from copolymers and polymers comprising ethylene, vinyl acetate, butadiene, styrene, vinyl chloride, acrylic esters, urethanes, and mixtures thereof.

7. The filter according to any one of claim 1 to 6, wherein the water-soluble binder is starch and the latex has a glass transition temperature from -10°C to 20°C and is a copolymer of ethylene and vinyl acetate.

8. The filter according to any one of claim 1 to 7, wherein the natural fibers are chosen from wood fibers, leaf fibers, fruit fibers, seed fibers, bast fibers, stalk fibers, reed fibers, and mixtures thereof.

9. The filter according to claim 8 wherein the wood fibers are chosen from hardwood pulp, bleached hardwood pulp, softwood pulp, bleached softwood pulp, softwood fluff pulp, bleached softwood fluff pulp, lyocell fibers, viscose fibers, and mixtures thereof.

10. Filter according to any one of claims 1 to 9 for a smoking or vaping article.

11. Smoking article comprising a filter as defined in Claim 10.

12. Vaping article comprising a filter as defined in Claim 10.

13. A nonwoven substrate comprising natural fibers and a binder, wherein the binder is a mixture of a water-soluble binder and a latex.

14. Process for producing a filter as defined in any one of claim 1 to 10, said process comprising the following steps: a) forming a rod of nonwoven substrate from a nonwoven substrate, b) wrapping the rod of nonwoven substrate with a sheet of plug wrap paper, c) depositing an adhesive line, joining the sheet of plug wrap paper to obtain a rod of filtering material, d) cutting the rod of filtering material to produce the filter.

15. Process for producing the nonwoven substrate as defined in claim 13 comprising the following steps: i) producing a web from natural fibers by an airlaid process or a drylaid process, ii) introducing the binder into the web, and iii) drying the web resulting from step ii) to obtain the nonwoven substrate.

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