Thermoplastic-impregnated cellulosic nonwovens as compostable filter materials for liquids

Abstract

The present invention relates to a heat-sealable filter material for liquids that is fully compostable. The filter material has a capacity of 50-1000 L / m 2 The filter material is a thermoplastic-impregnated cellulose nonwoven having a Textest air permeability of 100%. The filter material can be laminated to a support layer without the use of additional adhesives. Further aspects of the invention include compostable packaging elements comprising the compostable filter material described herein.

Description

[Technical field]

[0001] The present invention relates to a heat-sealable thermoplastic-impregnated cellulosic nonwoven fabric that can be used as a compostable filter material for liquids such as tea or coffee. A further aspect of the present invention includes a compostable packaging element comprising the compostable filter material described herein. [Background technology]

[0002] As environmental protection requirements become increasingly stringent, the use of sustainable materials also plays an important role in the food industry. Packaging materials play a key role in the pollution of the environment. Especially for single servings, the packaging rate is very high. Products that fall into this category are beverage elements such as infusion bags or capsules for disposable preparation.

[0003] Various approaches to replace the individual components of the packaging material have been investigated. In the beverage components mentioned above, the filter material is a key component. The filter material is generally made of nonwoven fabrics, such as wet-laid, spunbond, or meltblown materials. In order to use nonwoven fabrics in the manufacture of packaging materials, a key feature is heat sealability. In nonwoven fabrics, such heat sealability properties are generally imparted by thermoplastic fibers.

[0004] More sustainable bio-based thermoplastic fibers can be used to manufacture nonwoven fabrics that can be used as beverage components. These fibers are compostable, making the beverage components even more sustainable. For example, in WO2017 / 187024A1, a multi-layer composite of polylactic acid (PLA) spunbond bonded to a vegetable parchment layer was proposed to seal the beverage capsule (see FIG. 1A). The PLA spunbond material serves two main functions: first, it acts as a sealing layer on the capsule. Second, it has a filter function to prevent ground coffee from leaving the coffee capsule. However, the adhesives currently used for lamination of spunbond and vegetable parchment are not compostable.

[0005] In a different approach, a wet formula containing cellulose and PLA fibers can be used as a heat-sealable medium for tea bags or as a filter for coffee pods. This product has a lower carbon footprint than other purely synthetic nonwovens used as tea bags. Nevertheless, PLA fibers are only compostable under certain conditions, especially in industrial environments, as specified in EN13432. One of the important parameters is the temperature for composting. For a sample to pass the industrial composting test, it needs to be 55-60 °C. This is, of course, far from the thermal conditions of a home composter. Replacing PLA fibers with other types of biopolymer fibers is a difficult task, since fiber spinning is a complex process. Moreover, the price of synthetic biopolymers remains relatively high.

[0006] Another approach for coffee capsule lids is to use an extrusion coating or varnish coating on the parchment layer instead of the nonwoven layer that acts as the heat seal layer. However, this solution would not be satisfactory because the nonwoven layer also acts as a filter. The extrusion layer forms a continuous film. When used in coffee capsule lids, this film would create some air bubble effect, which is undesirable during the infusion step. Summary of the Invention [Problem to be solved by the invention]

[0007] There is therefore a demand for a heat-sealable filter material for liquids that is fully compostable, preferably home compostable. The heat-sealability should be obtained without the use of additional adhesive layers that raise sustainability issues. Such a filter material should have well-established or even improved leaching properties. Furthermore, the filter material should be available in a simple manner and at low cost. Furthermore, there is a demand for a compostable packaging element that includes the compostable filter material. [Means for solving the problem]

[0008] The present invention solves the problems of the prior art by providing a thermoplastic-impregnated cellulose nonwoven as a filter material for liquids. By impregnating a cellulose nonwoven with a thermoplastic binder, the present invention provides a surprisingly simple solution for achieving a heat-sealable filter material. Such a thermoplastic-impregnated cellulose nonwoven can be laminated to a support layer without the use of additional adhesives.

[0009] Cellulosic fibers are known as biodegradable packaging materials. As a result, the plain composition of the thermoplastic-impregnated cellulose nonwoven fabric of the present invention makes the compostability dependent only on the thermoplastic binder. Depending on the binder selected, the filter material of the present invention may be home compostable. Thus, the filter material shows enhanced biodegradability and decomposition rate after disposal.

[0010] Surprisingly, it has been found that the particular air permeability confers improved percolation properties to the filter material of the present invention compared to beverage filter materials known in the art. In particular, the filter material has a permeability of 50 to 1000 L / m at 196 Pa. 2·Texture has the best air permeability.

[0011] Additionally, the present invention also provides a compostable packaging element comprising a compostable filter material, the primary application of which is in beverage applications, including lidding solutions for heat sealable beverage filters, such as filters for single-serving coffee capsules or tea bags or coffee pods.

[0012] The present invention includes the following embodiments. Embodiment 1. A compostable filter material for liquids, comprising: The filter material is a heat-sealable thermoplastic-impregnated cellulose nonwoven fabric, and the filter material has a permeability of 50 to 1000 L / m at 196 Pa, measured in accordance with ISO 9237. 2 · Compostable filter material with the best air permeability.

[0013] Embodiment 2. 2. The compostable filter material of embodiment 1, wherein the filter material has a pore size distribution comprising a smallest pore having a smallest pore size and a largest pore having a largest pore size, and the average pore size of the filter material is between 10 and 60 μm.

[0014] Embodiment 3. A compostable filter material according to embodiment 2, wherein the largest pores have a maximum pore size of at least 50 μm, preferably 50 to 120 μm.

[0015] Embodiment 4. The compostable filter material according to embodiment 3, wherein the smallest pores have a minimum pore size of 1 to 30 μm.

[0016] Embodiment 5. 5. The compostable filter material of any one of embodiments 1 to 4, wherein the thermoplastic-impregnated cellulosic nonwoven comprises a cellulosic nonwoven material and at least one thermoplastic binder, and the cellulosic nonwoven material comprises cellulosic fibers.

[0017] Embodiment 6. the amount of thermoplastic binder is 10-75% by weight, based on the total weight of the thermoplastic-impregnated cellulosic nonwoven fabric; and / or 6. The compostable filter material according to embodiment 5, wherein the thermoplastic binder is a compostable binder, preferably, the thermoplastic binder is a home compostable binder.

[0018] Embodiment 7. the amount of cellulosic fibers in the cellulosic nonwoven material is 90% by weight or more, based on the total weight of the cellulosic nonwoven material; and / or the cellulosic fibres are natural or man-made cellulose fibres or a mixture of both, the cellulosic fibres preferably being a mixture in which the ratio of natural to man-made cellulose fibres is between 7:3 and 9:0.5; and / or 7. The compostable filter material of embodiment 6, wherein the thermoplastic binder is one or more selected from the group consisting of polyurethane, polybutylene succinate, and polylactic acid, preferably the thermoplastic binder is polyurethane.

[0019] Embodiment 8. The thermoplastic-impregnated cellulosic nonwoven fabric has a fiber thickness of at least 15 g / m 2 , preferably 20 to 90 g / m 2 and / or The thermoplastic-impregnated cellulose nonwoven fabric has a thickness of at least 60 μm, preferably between 80 and 150 μm, and / or 8. The compostable filter material according to any one of the preceding embodiments, wherein the thermoplastic-impregnated cellulose nonwoven fabric has an average flow pore diameter of 10 to 50 μm.

[0020] Embodiment 9. A compostable packaging element comprising a compostable filter material according to any one of embodiments 1-8.

[0021] Embodiment 10. A compostable packaging element according to embodiment 9, wherein the compostable packaging element is a coffee capsule, a lid for a coffee capsule, or a tea bag.

[0022] Embodiment 11. A compostable packaging element according to embodiment 10, wherein the compostable packaging element is a lid for a coffee capsule, the lid further comprising a cellulose support layer.

[0023] Embodiment 12. A method for producing a compostable filter material according to any one of embodiments 1 to 11, comprising: i) providing a cellulosic nonwoven fabric; ii) impregnating the cellulosic nonwoven fabric with a thermoplastic binder.

[0024] Embodiment 13. Use of a compostable filter according to any one of embodiments 1 to 11 in a method for producing coffee.

[0025] Where the present description refers to "preferred" embodiments / features, a combination of these "preferred" embodiments / features is also deemed to be disclosed, so long as this combination of "preferred" embodiments / features makes technical sense.

[0026] Hereinafter, use of the term "comprising" should be understood as disclosing, as a more limited embodiment, the term "consisting of," insofar as this is technically meaningful. [Brief description of the drawings]

[0027] [Figure 1A] A "Nespresso" type beverage capsule outside the scope of the present invention having a multi-layered lid of PLA spunbond adhered to a vegetable parchment support by a non-compostable adhesive. [Figure 1B] A "Nespresso" type beverage capsule according to the invention having a heat-sealable thermoplastic-impregnated cellulose nonwoven as a compostable filter material for the liquid. [Diagram 2]A "K-Cup" type beverage capsule according to the present invention having a heat-sealable thermoplastic-impregnated cellulose nonwoven as a compostable filter material for the liquid. [Diagram 3] FIG. 1 is a schematic diagram of impregnating a nonwoven fabric with a thermoplastic binder. [Figure 4A] FIG. 1 is a schematic diagram of impregnating a cellulosic nonwoven fabric with a thermoplastic binder while the binder is still wet and assembling it to a support layer. [Figure 4B] FIG. 1 is a schematic diagram of impregnating a cellulosic nonwoven fabric with a thermoplastic binder that is assembled after drying and laminated to a support layer with a small amount of binder. [Figure 4C] FIG. 1 is a schematic diagram of impregnating a cellulose nonwoven fabric with a thermoplastic binder by laminating the cellulose nonwoven fabric directly to a support layer on which a sufficient amount of thermoplastic binder is deposited to impregnate the cellulose nonwoven fabric. [Diagram 5] FIG. 2 is a particle size distribution of the coffee samples used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention relates to a compostable filter material for liquids, the filter material being a heat-sealable thermoplastic-impregnated cellulose nonwoven fabric, with a flow capacity of 50-1000 L / m at 196 Pa. 2 ·Texture has the best air permeability.

[0029] In the context of the present invention, the following definitions and methods of analysis apply. As mentioned above, a first aspect of the invention relates to a filter material that is compostable. The term "compostable" is generally defined in line with EN13432. The term "compostable filter material" refers to a filter material that contains up to 10% by weight, preferably 5% by weight, of non-compostable components, thereby fulfilling EN13432. When applied to a material or product, the term "compostable" means that the entire material or product biodegrades and disintegrates. "Biodegrade" means that a chemical structure or material breaks down under the action of microorganisms. The term "disintegrate" means that the material or product made therefrom physically disintegrates into fine, visually indistinguishable pieces at the end of a typical composting cycle.

[0030] An "industrially compostable" material may be compostable as described above in an industrial environment. The material may disintegrate and biodegrade at temperatures between 55°C and 60°C in less than 6 months. In particular, disintegration in an industrial environment may take less than 3 months, while biodegradation may take less than 6 months. If a material is described as "home compostable", it is compostable as described above under conditions present in a home composter environment. The material may disintegrate and biodegrade at temperatures below 55°C, preferably between 10 and 45°C, most preferably between 25 and 30°C, in less than 12 months. In particular, disintegration may take less than 6 months, while biodegradation may take less than 12 months in a home composter environment.

[0031] The present invention is compostable as described above, since it contains at least one compostable thermoplastic binder. To be considered a "compostable thermoplastic", the thermoplastic chains must be degraded under the action of microorganisms, so that total mineralization is achieved at a high rate compatible with the normal composting process of vegetable waste. The term "mineralization" refers to the conversion of materials into CO2, water, inorganic compounds, and biomass under aerobic conditions.

[0032] As used herein, "thermoplastic binder" refers to a plastic polymer that becomes moldable at some elevated temperature and solidifies upon cooling. Any thermoplastic compostable binder is suitable for providing the heat sealable filter material of the present invention. Preferably, the thermoplastic binder is a home compostable binder. Preferably, the thermoplastic binder may have a melting temperature of 200-95°C, preferably 200-100°C, more preferably 190-105°C, and most preferably 180-110°C. Exemplary binder emulsions according to the present invention include polyurethane (PU), polybutylene succinate (PBS) and PLA. A preferred thermoplastic binder may be polyurethane. The binder may be home compostable, thus providing a heat sealable filter material with enhanced biodegradability and degradation rate after disposal. Examples of home compostable PU binders include modified PU, i.e., PU modified by the insertion of one or more additional monomers via copolymerization into the PU, such as SciTech's ST6515.

[0033] An important aspect of the present invention is a compostable filter material for liquids. As used herein, the term "filter material" refers to a solid material suitable for filtration. Thus, the filter material of the present invention is inert when used in liquids. In other words, once the thermoplastic binder is dried, it is neither soluble nor crosslinked in the liquid.

[0034] "Filtration" in the context of the present invention describes the process of physical separation by using a filter material. The "filter material for liquids" referred to herein has a complex structure through which the liquid, called filtrate, and particulates below a certain size can pass. Particles above a certain size cannot pass through the filter material and form a filter cake on top of the filter material.

[0035] The filter material used in the present invention may include a cellulosic nonwoven material, which contains cellulosic fibers and is fully home compostable as defined above. The term "nonwoven" can be used interchangeably with the term "paper" for the purposes of the present invention, unless otherwise specified. The term "cellulosic nonwoven" refers to a fabric-like sheet having a structure of individual fibers derived or prepared from cellulose. They are intertwined and interwoven with each other, but not in a identifiable manner like woven or knitted fabrics. Nonwoven fabrics can be formed from many processes, such as, for example, spinlaying, carding, airlaying (also known as drylaying) and waterlaying processes. These result in spinlaid, carded, airlaid (also known as drylaid), and wetlaid nonwoven fabrics, respectively.

[0036] The cellulose nonwoven fabric used in the present invention can preferably be a wet-laid nonwoven fabric made on a paper machine. A wet-laid nonwoven fabric can be produced by suspending fibers in water and pumping the dispersion to continuously deposit the fibers on a forming wire before the water is withdrawn. The cellulose nonwoven fabric can have a single layer structure or a two-layer or multi-layer structure. A cellulose nonwoven fabric having at least a two-layer structure can be obtained using a paper machine equipped with a headbox having multiple compartments. The different layers are formed simultaneously on the continuously moving forming wire of the paper machine. A cellulose nonwoven fabric having at least two layers can be obtained without using a binder between the layers.

[0037] As used herein, the term "fiber" refers to a material form characterized by a very high ratio of length to diameter. Generally, cellulose fibers (natural and artificial) have a variety of diameters and lengths that depend on the type of fiber and the source of the fiber. The average length of the fibers preferably used in the filter material of the present invention may range from 0.1 mm to 12 mm, preferably from 1 mm to 10 mm. The diameter of the fibers may range from 10 μm to 50 μm, preferably from 10 μm to 40 μm. Thus, the aspect ratio of the fibers (ratio of fiber length to fiber diameter) may range from 2 to 1,200, preferably from 25 to 1,000. The terms "fiber" and "filament" may be used interchangeably for the purposes of the present invention, unless otherwise specified.

[0038] The cellulose nonwoven fabric of the present invention consists essentially of cellulose. It may comprise natural cellulose fibers, including pulp, or artificial cellulose fibers, or a mixture of both. Artificial cellulose fibers are also known as regenerated cellulose fibers. There are two main classes of regenerated cellulose: Lyocell and viscose, also known as rayon. The cellulose nonwoven fabric may preferably comprise natural cellulose fibers and artificial cellulose fibers. The ratio of natural cellulose to artificial cellulose fibers in the cellulose nonwoven fabric of the present invention may be 7:3 to 9:0.5, preferably 8:2.5 to 9:1. The total cellulosic fiber content may be greater than 90% by weight, preferably greater than 95% by weight, more preferably greater than 97% by weight, based on the total weight of the nonwoven fabric. The cellulose nonwoven fabric may further comprise less than 10% by weight, preferably less than 5% by weight, more preferably less than 3% by weight of additives, based on the total weight of the nonwoven fabric. Such additives may include carboxymethyl cellulose (CMC) and PAE (polyamide-epichlorohydrin) Kymene as binders. CMC may function as a binder to improve the quality of the paper. PAE Kymene can function as a wet strength agent, but since the latter is not biodegradable, it is preferable to keep the amount low.

[0039] In particular, the cellulose nonwoven fabric may contain 0% to 55%, preferably 15% to 55%, more preferably 25% to 54% natural cellulose pulp from annual plants, based on the total weight of the nonwoven fabric. Natural cellulose pulp from any annual plant suitable for providing the desired properties of the present invention can be used. An example of an annual plant is abaca. Abaca fibers tend to be relatively long. They can be introduced to provide mechanical strength to the cellulose nonwoven fabric, which is particularly important in the paper manufacturing process.

[0040] Cellulosic nonwovens may also include refined cellulose materials. Refining is a mechanical treatment that causes fibrillation and, to some extent, breakage of the cellulose fibers. An indication of the level of refinement is the Schopper-Riegler degree (°SR). The Schopper-Riegler degree specifies the degree of freedom of suspension of the fibers. A larger °SR equates to slower drainage. The °SR values ​​used herein were measured according to a method conforming to ISO5267-1:1999.

[0041] The cellulosic nonwoven fabric may contain 0% to 40% by weight, preferably 15% to 38% by weight, more preferably 30% to 36% by weight, of softwood fibers and 0% to 55% by weight, preferably 25% to 54% by weight, more preferably 45% to 52% by weight, of hardwood fibers, based on the total weight of the nonwoven fabric. The softwood fibers are smaller in length compared to abaca fibers, but longer than hardwood fibers. Softwood and hardwood fibers are the most commonly used fibers in papermaking. The softwood and hardwood fibers may be refined to have a refining level of 30 to 60° SR.

[0042] Furthermore, the cellulosic nonwoven fabric may contain 0% to 10% by weight, preferably 2% to 9% by weight, more preferably 5% to 8% by weight of floc, based on the total weight of the nonwoven fabric. Floc is highly refined cellulosic pulp, softwood and hardwood floc, which is usually softwood or hardwood pulp subjected to very high refining, may have a level of refinement of 75 to 85° SR. Floc may be used to obtain a denser pore structure in the nonwoven fabric.

[0043] In addition, the cellulosic nonwoven fabric may contain 0% to 30% by weight, preferably 5% to 25% by weight, of lyocell and rayon, each independently based on the total weight of the nonwoven fabric. These fibers tend to have a larger diameter and tend to be longer compared to natural cellulosic fibers. They also tend to be smooth and not have many fibrils. Man-made cellulosic fibers are useful for opening up the structure of cellulosic nonwoven fabrics.

[0044] Finally, the cellulosic nonwoven fabric may contain, either independently or in combination, 0% to 1.5%, preferably 0.5% to 1.3%, more preferably 0.9% to 1.2% by weight of a wet strength agent, such as PAE Kymene, and 0% to 3%, preferably 1% to 2.8%, more preferably 2% to 2.7% by weight of a binder, such as CMC, each based on the total weight of the nonwoven fabric.

[0045] In one embodiment, the cellulosic nonwoven fabric of the present invention may comprise, based on the total weight of the nonwoven fabric, 0% to 55% by weight of natural cellulosic pulp from annual plants, preferably abaca, 0% to 40% by weight of softwood, 0% to 55% by weight of hardwood, 0% to 10% by weight of flock, 0% to 20% by weight of lyocell, 0% to 20% by weight of rayon, 0% to 1.5% by weight of PAE Kymene, and 0% to 3% by weight of CMC.

[0046] In a preferred embodiment, the cellulosic nonwoven fabric may comprise, based on the total weight of the nonwoven fabric, 15% to 55% by weight of natural cellulosic pulp from annual plants, preferably abaca, 15% to 38% by weight of softwood, 25% to 54% by weight of hardwood, 2% to 9% by weight of flock, 5% to 16% by weight of lyocell, 5% to 16% by weight of rayon, 0.5% to 1.3% by weight of PAE Kymene, and 1% to 2.8% by weight of CMC.

[0047] In a more preferred embodiment, the cellulosic nonwoven fabric may comprise, by weight, 25% to 54% natural cellulosic pulp from annual plants, preferably abaca, 30% to 36% softwood, 45% to 52% hardwood, 5% to 8% flock, 8% to 14% lyocell, 8% to 14% rayon, 0.9% to 1.2% PAE Kymene, and 2% to 2.7% CMC, based on the total weight of the nonwoven fabric.

[0048] In certain preferred embodiments, the cellulosic nonwoven fabric of the present invention may be comprised of 52% abaca, 34.7% softwood, 9.6% rayon, 2.6% CMC, and 1.1% PAE Kymene by weight based on the total weight of the nonwoven fabric. In another particular preferred embodiment, the cellulosic nonwoven fabric of the present invention may be comprised of 28.6% abaca, 50.9% hardwood, 7.6% flock, 12% lyocell, and 1% PAE Kymene by weight based on the total weight of the nonwoven fabric.

[0049] The cellulosic nonwoven fabrics of the present invention can have any basis weight and thickness suitable to provide the desired properties for the beverage component. As used herein, the term "basis weight" refers to the areal density of the paper product. The basis weight of a nonwoven fabric is usually measured as the weight per unit area, e.g., grams per square meter (gsm = g / m 2) or ounces per square foot (osf). The terms "basis weight" and "gram weight" can be used interchangeably for the purposes of the present invention, unless otherwise specified. As used herein, basis weight was measured according to standard ISO 536. Prior to the impregnation step, the cellulosic nonwoven fabric has a weight of at least 12 g / m 2 , preferably 16 to 60 g / m 2 , more preferably 18 to 45 g / m 2 , and most preferably 20 to 38 g / m 2 The thermoplastic impregnated cellulosic nonwoven may have a basis weight of at least 15 g / m 2 , preferably 20 to 90 g / m 2 , more preferably 22 to 70 g / m 2 , and most preferably 25 to 40 g / m 2 Furthermore, the impregnated cellulosic nonwoven fabric may have a thickness, measured according to standard ISO 534, of at least 60 μm, preferably between 80 and 150 μm, more preferably between 85 and 140 μm.

[0050] An important aspect of the present invention relates to the thermoplastic impregnated cellulose nonwoven fabric being heat sealable. As used herein, the term "heat sealable" refers to a hot melt property that allows the material to be thermally bonded. The heat sealability of the filter material of the present invention may result from impregnating the cellulose nonwoven fabric with a thermoplastic binder emulsion, as described in more detail below. The amount of binder in the filter material after impregnation may be 10-75% by weight, preferably 33-66% by weight, based on the total weight of the thermoplastic impregnated cellulose nonwoven fabric. It has been found that the heat sealability, leaching properties, and resistance of the filter material are excellent when the filter material contains a binder in an amount within the range specified above. Using a thermoplastic binder in an amount less than 10% by weight may result in insufficient impregnation of the nonwoven fabric. On the other hand, when more than 50% by weight of binder is used, the filtration ability may be poor.

[0051] As mentioned above, one main aspect of the present invention is a gas permeability test for a gas permeability range of 50 to 1000 L / m at 196 Pa. 2Textest air permeability of .s. The expression "air permeability" referred to in this specification is the speed of air flow passing vertically through a known area under a given air pressure difference between two surfaces of the material. The concept of "air permeability" is widely used in the textile industry to interpret the intrinsic properties of fabrics. Air permeability is influenced by the material and structural properties of the fabric, including the individual pore structure. The fluid dynamics of coffee extraction are influenced by the permeability of the coffee bed and the filter material. In other words, the interplay between the material and pore size of the filter on the one hand and the degree of coffee grinding on the other hand can be important with regard to the coffee extraction fluid dynamics. However, ground coffee used for extraction in coffee capsules under high pressure usually has a standardized degree of grinding that includes a large amount of fine particles (less than 100 μm). Therefore, in the case of coffee capsules, the fluid dynamics are mainly influenced by the material and pore size of the filter. However, these two parameters affect the air permeability of the filter material.

[0052] Several existing standards can be used for air permeability evaluation with different test conditions. The air permeability of the filter material of the present invention was measured by Textest air permeability at 196 Pa according to standard ISO 9237. This standard is suitable for fairly open structures such as nonwoven fabrics. The inventors have surprisingly found that thermoplastic-impregnated cellulose nonwoven fabrics have an air permeability of 50-1000 L / m at 196 Pa. 2 s, preferably 100 to 700 L / m at 196 Pa 2 s, more preferably 200 to 500 L / m at 196 Pa 2 s, most preferably 220-500 L / m at 196 Pa 2 It has been found that the filter material has improved permeability when it has a Textest air permeability of s.

[0053] Surprisingly, this is true for coffee capsules and tea bags as well, although these two beverage components have completely different requirements. Without wishing to be bound by theory, this may be due to the completely opposite pressure-time relationship in the two components. In other words, filtration in coffee capsules takes place under high pressure within a relatively short period of time, while tea preparation involves a pressure-free diffusion process over a much longer period of time.

[0054] As a filter material for liquids in beverage applications, 50 L / m at 196 Pa 2 If a thermoplastic-impregnated cellulose nonwoven fabric with a Textest air permeability below .s is used, the infusion properties deteriorate. As described below, if such a material is used to prepare the lid of a coffee capsule, dripping, i.e. irregular flow, can occur during extraction. Furthermore, very high pressures can develop inside the capsule, which can even burst. As described in more detail below, if the material is used to prepare a tea bag or filter for a coffee pod, a very low flow rate and therefore a very long extraction time results.

[0055] As a filter material for liquids in beverage applications, 1000 L / m at 196 Pa 2 When using thermoplastic-impregnated cellulose nonwovens with a Textest air permeability exceeding .s, the infusion characteristics may also be disturbed. When using materials such as coffee capsule lids, very high pressures or dripping may be observed during extraction. Furthermore, the volume obtained may be very low.

[0056] Another possibility to measure the air permeability is to measure it according to the ISO 5636-3 standard, commonly called "Bendtsen porosity". According to this standard, the air permeability is measured according to the ISO 5636-3 standard, which is commonly called "Bendtsen porosity" according to the ISO 5636-3 standard. 2The samples are subjected to a pressure difference of 1.47 kPa to measure the air permeability. This standard is valid for air permeabilities of 30 to 1327 mL / min and is generally used for materials with a fairly dense pore structure. To facilitate the comparison of the Textest air permeability with the Bendtsen porosity below, Table 1 shows the difference between the values ​​obtained for the three paper samples.

[0057] [Table 1]

[0058] Without wishing to be bound by any theory, Table 1 shows an approximately linear dependence between the values ​​obtained by the methods according to ISO 9237 and ISO 5636-3. However, the results shown in Table 1 predict that the filter material of the present invention, having a Textest air permeability as specified above, will have a Bendtsen porosity that is much higher than the upper range of 1327 mL / min specified by ISO 5636-3. In fact, a Bendtsen porosity of more than 5000 mL / min at 1.47 kPa has been measured for the filter material of the present invention. When following the method of the ISO 5636-3 standard, the analysis is limited to 5000 mL / min, so that an exact value cannot be determined by this method. Nevertheless, this measurement confirms that the filter material of the present invention does not meet the requirement of a tight pore structure according to the ISO 5636-3 standard.

[0059] As mentioned above, air permeability can be influenced not only by the composition of the material, but also by its structural properties, i.e., the individual pore structure. The pore size in the cellulose nonwoven fabric is determined by a porometer, using a Porometer (Porolux1000), and is reported in microns (μm). The filter material of the present invention has a pore size distribution including the smallest pores having the smallest pore size and the largest pores having the largest pore size. The average pore size of the filter material is calculated from the average of the pore sizes in the filter material determined by the porometer and can be 10-60 μm, preferably 14-50 μm, more preferably 18-45 μm, and most preferably 20-40 μm. The largest pores of the filter material can have a maximum pore size of at least 50 μm, preferably 50-120 μm, more preferably 55-100 μm, and most preferably 60-90 μm. The smallest pores of the filter material can have a minimum pore size of 1-30 μm, preferably 2-20 μm, more preferably 4-15 μm, and most preferably 5-10 μm.

[0060] Within these ranges the infusion properties of the filter material can be improved, which applies equally to beverage components such as coffee capsules used under high pressure and to beverage components such as tea bags used under high pressure, for the reasons envisaged above.

[0061] As already explained, the hydrodynamics of coffee extraction also depends on the pore size of the filter material. The improved performance of the filter material of the present invention cannot be achieved with pore sizes below or above the ranges specified herein, for the reasons described above with respect to permeability. If a pore size much above the above ranges is used, the nonwoven fabric will no longer be suitable as a filter material, because the particles will no longer be separated from the liquid and will also pass through the nonwoven fabric. On the other hand, if a pore size below the above ranges is used, the nonwoven fabric will no longer be suitable as a filter material.

[0062] In one embodiment, the filter material of the present invention may have smallest pores with a minimum pore size of 1-30 μm, largest pores with a maximum pore size of at least 50 μm, and an average pore size of 10-60 μm.

[0063] In a preferred embodiment, the filter material of the present invention may have smallest pores with a smallest pore size of 2-20 μm, largest pores with a largest pore size of 50-120 μm, and an average pore size of 14-50 μm.

[0064] In a more preferred embodiment, the filter material of the present invention may have smallest pores with a smallest pore size of 4-15 μm, largest pores with a largest pore size of 55-100 μm, and an average pore size of 18-45 μm.

[0065] In a most preferred embodiment, the filter material of the present invention may have smallest pores with a minimum pore size of 5-10 μm, largest pores with a maximum pore size of 60-90 μm, and an average pore size of 20-40 μm.

[0066] Furthermore, when measuring the pore size by porometer (Porolux1000), the mean flow pore diameter may be determined. The mean flow pore diameter is the diameter at which 50% of the flow passes through the larger pore. The mean flow pore diameter of the filter material of the present invention may be 10-50 μm, preferably 15-40 μm, more preferably 20-35 μm.

[0067] It has been found that when using beverage elements comprising filter materials with a mean flow pore diameter within the ranges specified above, the infusion characteristics are particularly improved when the filter materials are used in beverage elements, for example coffee capsules or tea bags, despite the completely different demands placed on these two beverage elements for the reasons already considered above. When filter materials with a mean flow pore diameter above or below the inventive ranges specified herein are used in beverage elements, the performance may be degraded for the reasons mentioned above with regard to permeability.

[0068] In another embodiment, the present invention relates to a compostable packaging element comprising the filter material as described in detail above. The packaging element may be a beverage packaging element. The beverage packaging element may be a tea bag, a coffee filter, a filter for a beverage pod, or a lid intended to seal a beverage capsule, for example a coffee capsule. Some of the common coffee capsules on the market are the "Nespresso" type illustrated in Figures 1A and 1B, and the "K-Cup" type illustrated in Figure 2. However, the packaging element of the present invention comprising the filter material as described in detail above may include further types of coffee capsules not explicitly mentioned herein.

[0069] In a preferred embodiment, the beverage component is a lid for a coffee capsule. The beverage packaging component may further comprise a cellulose support layer assembled with the compostable filter material of the present invention to form a lid suitable for sealing the beverage capsule. In the coffee capsule, high pressure is generated during coffee brewing. This high pressure deforms the capsule lid until the lid-controlled hole opens. The support layer allows the lid to withstand the pressure inside the capsule until it bursts. The support layer may comprise a cellulose portion, which may be a monolithic cellulose structure such as vegetable parchment, glassine paper or tracing paper.

[0070] As used herein, the term "vegetable parchment" refers to paper made by treating a cellulose paper sheet with a gelatinizing agent, including, for example, sulfuric acid, under conditions where the reaction time between the gelatinizing agent and the cellulose is limited to controlling the dissolution, hydrolysis, and degradation of the cellulose. The treated paper is then thoroughly washed to remove the gelatinizing agent, and is then dried. The bath chemicals partially dissolve or gelatinize the cellulose in the paper sheet. The dissolved cellulose then precipitates when the bath chemicals are diluted by washing the treated paper. This process is called parchmentization or parchmentation, and forms a very tough, stiff, smooth paper, with a true parchment-like appearance. Papers treated in this way tend to become brittle and wrinkle when dried, so they are sometimes treated with a plasticizer, such as glycerin, glucose, or sorbitol. Vulcanized fiber is a related product made by treating a cellulose paper sheet with a gelatinizing agent, including, for example, zinc chloride.

[0071] As used herein, the expression "glassine paper" refers to paper obtained by supercalendering a nonwoven fabric, i.e. paper. The repeated moistening and calendaring during the supercalendering process produces a very dense and nonporous paper. As used herein, "tracing paper" is paper obtained from an aqueous suspension of paper pulp that has undergone a very high level of refining, which is also a very dense and nonporous cellulose fiber.

[0072] The support layer may optionally include an oxygen barrier layer, 2 Less than one day, preferably 0.1 to 1.5 mL / m 2 1 day, preferably 0.5 to 1 mL / m 2 The term "oxygen transmission rate" of a material refers to the rate at which oxygen permeability through a specified area (m2) of the material increases during a day at an atmospheric pressure of 1.013 bar (1 atm), a temperature of 23°C, and a relative humidity of 50%. 2 OTR (mL / m2 The OTR (Optical Torrency Rate) is measured according to ASTM D3985 and ASTM F1927. The OTR of a material is a measure of the gas barrier properties of the material and indicates the gas barrier level. In other words, the lower the OTR of a material, the less amount of gas will permeate through the material, and as a result, the material provides a high barrier to gases, especially oxygen.

[0073] The present invention relates to a simple and inexpensive method for preparing a compostable filter material for liquids according to the invention. As already mentioned above, replacing the commonly known PLA fibers with other types of biopolymer fibers is a difficult task due to the complex fiber spinning process. Moreover, the price of synthetic biopolymers remains relatively high.

[0074] According to the method of the present invention, the compostable filter material defined above comprises: i) providing a cellulosic nonwoven fabric; and ii) impregnating the cellulosic nonwoven fabric with a thermoplastic binder.

[0075] The impregnation of the cellulose nonwoven itself can be carried out according to the following process. First, as shown in FIG. 3, a cellulose nonwoven fabric having the above-mentioned characteristics may be impregnated with an emulsion containing a thermoplastic binder (optionally 30% to 60% of the dry solids content) as described above. The emulsion containing the thermoplastic binder may preferably be an aqueous emulsion, more preferably water. The impregnation step may be carried out via any method suitable for achieving the filter material of the present invention. For example, impregnation may be carried out by applying a thermoplastic binder to the nonwoven fabric and, optionally, passing it through a roll to remove excess binder. Impregnation may also be carried out by inserting or immersing the nonwoven fabric in a bath or by spraying the thermoplastic binder onto the nonwoven fabric. The impregnation process may be discontinuous or continuous, i.e., the entire nonwoven fabric may be subjected to one of the aforementioned processes at once, or individual sections of the nonwoven fabric may be subjected to one after the other.

[0076] After the impregnation step, the nonwoven fabric may be further treated in optional steps, as described for the lids of coffee capsules below, before the following steps are carried out.

[0077] In a second step, the impregnated cellulose nonwoven may be dried. The drying process may be carried out at room temperature or at a higher temperature. Drying the impregnated nonwoven at a higher temperature may be beneficial in terms of time and therefore in production efficiency. Care must be taken to ensure that the drying time is adjusted accordingly, i.e., shortened, when the temperature is increased to prevent possible degradation. For example, the impregnated nonwoven may be dried at 90° C. for 1 minute. The drying process may further be carried out under static or non-static conditions, in air, in an inert gas such as argon or nitrogen, or under reduced pressure.

[0078] Furthermore, the present invention relates to a simple and inexpensive method of preparing a packaging element, preferably a beverage packaging element, comprising a filter material as detailed above.

[0079] Due to the heat sealability of the filter material of the present invention, a portion of the thermoplastic impregnated cellulosic nonwoven fabric can be heat bonded to another article and / or another portion of the filter material. For example, a sheet of filter material can be heat sealed at its edge regions to another sheet of filter material to form a pouch-like structure, such as a tea bag or coffee filter.

[0080] In another approach, a sheet-like filter material can be assembled and laminated to a support layer as described above to provide a lid for the coffee capsule of the present invention. In the following, three exemplary methods for providing a lid for the coffee capsule of the present invention are described in more detail.

[0081] In the first method (FIG. 4A), a cellulosic nonwoven fabric may be impregnated with the thermoplastic binder emulsion of the present invention according to the above-described first step for preparing an impregnated nonwoven fabric. However, in a further step, the impregnated nonwoven fabric may be assembled to a support layer, as described in detail above, while still wet with the binder. After forming the laminate, drying is carried out.

[0082] In the second method (FIG. 4B), a cellulose nonwoven fabric can be impregnated with the binder of the present invention in a first step and dried in the second step described above. The dried impregnated nonwoven fabric can then be assembled and laminated to a support layer as described above, the support layer being provided with a small amount of thermoplastic binder emulsion. The exact same binder emulsion can be used as that used to impregnate the nonwoven fabric in the first step, so no additional adhesive is required.

[0083] In the third method (FIG. 4C), a sufficient amount of thermoplastic binder is deposited in a first step on the support layer of the present invention, as explained in detail above, after which a cellulosic nonwoven fabric is laminated directly to the support layer while the nonwoven fabric is impregnated.

[0084] The untreated thermoplastic impregnated filter material, the pouch-like structure, and the laminated beverage capsule lid structure can be heat sealed to other components of the beverage entity, such as a coffee capsule (see Figures 1B and 2).

[0085] Furthermore, the present invention relates to the use of a compostable filter material according to any one of claims 1 to 11 in a method for producing coffee. The compostable filter material can be used as such at any operating pressure. This means that it can be used at atmospheric pressure as well as at elevated pressure, for example between 5 bar and 18 bar, without unintended breakdowns. EXAMPLES

[0086] Among the various end uses in beverage components contemplated by the filter material of the present invention, coffee capsule use is the one with the most limitations (see test protocol below). Therefore, the following samples are designed to illustrate the effect of the present invention using lids with different properties on "Nespresso" type coffee capsules. The properties of the lid samples investigated here are summarized in Table 2 below.

[0087] The following samples were prepared as follows: First, the nonwoven material (base) was impregnated with an aqueous emulsion containing about 40% of the dry solids of the thermoplastic binder. The impregnated material was then dried at 90°C for 1 minute. The dried impregnated nonwoven was then assembled into a support layer with a small amount of binder at the interface (see FIG. 4B). The total amount of emulsion binder was adjusted accordingly to achieve nonwovens with different binder amounts, as specified in Table 2. Once the filter material and vegetable parchment (support layer) were stacked, they were dried at 90°C for 1 minute. The sample was then pressed at 200kN by using a plate heated at 120°C for 5 seconds.

[0088] As support layers, two different types of vegetable parchment, PureBarrier or Sulflex (both from Ahlstrom-Munksjoe Oyj), were used in the following samples. PureBarrier has improved oxygen barrier properties compared to Sulflex.

[0089] The preferred binder used herein is the commercial polyurethane-based emulsion ST6515 from SciTech. In the comparative samples, acrylic latex mixtures (from Carbobond and Hycar) are used, but these binders are not home compostable. PLA and PBS-based emulsions (from Chukyo-Yushi and OVOL Japan Pulp & Paper GmbH, respectively) are also used, but the home compostability of these samples is not fully achieved according to the above definition.

[0090] Three grades of cellulose wet-laid nonwoven fabrics were used as substrates for preparing the filter materials of the present invention. The same nonwoven fabric substrates are used in samples 1-3 and 6-8. Samples 4, 5, and 9 each have different base papers independently. The recipes and properties of the different nonwoven fabrics are shown in Tables 3.1-3.3 below. Further properties of the nonwoven fabrics after the impregnation step are summarized for selected samples in these tables.

[0091] Comparison sample 1 PLA spunbond nonwoven base (20g / m 2 ) at 3 to 4 g / m 2 (acrylic mixture) and a support layer (PureBarrier, 70 g / m 2 The resulting laminate, except for the binder, is compostable in industrial environments as specified in EN13432.

[0092] Comparison sample 2 55g / m 2 Laminates were prepared as described for Comparative Sample 1, except that a PLA spunbond nonwoven base having a gram of 0.01 g was used.

[0093] Comparison sample 3 70g / m 2 A laminate was prepared as described for Comparative Sample 1, except that a PET / PE bicomponent needle-punched nonwoven base (from Ahlstrom-Munksjoe Oyj) having a gram weight of 100 g / m2 (100 g / m2) and an acrylic binder mixture binder were used. The resulting laminate is non-compostable.

[0094] Sample 1 CMC(37g / m 2 ) on a cellulose wet-laid nonwoven base, 4 g / m 2 A thermoplastic binder (SciTech) was applied to the support layer (PureBarrier, 70 g / m 2 ) and standard pressing. The resulting laminate is fully compostable in a home composter.

[0095] Sample 2 6g / m 2 Laminates were prepared as described for Sample 1, except that an amount of thermoplastic binder (SciTech) was used. The resulting laminates are fully compostable in a home composter.

[0096] Sample 3 12g / m 2 A laminate was prepared as described for Sample 1, except that an amount of another thermoplastic binder (SciTech) was used. The resulting laminate is fully compostable in a home composter.

[0097] Sample 4 25g / m 2 Laminates were prepared as described for Sample 2, except that only a different cellulose wet-laid nonwoven base was used without CMC having a gram of 0.01 g. The resulting laminates are fully compostable in a home composter.

[0098] Sample 5 31g / m 2 Laminates were prepared as described for Sample 2, except that only a different cellulosic wet-laid nonwoven base was used that did not contain CMC having a gram of 0.01 g. The resulting laminates are fully compostable in a home composter.

[0099] Sample 6 6g / m 2 A laminate was prepared as described for sample 1, except that an amount of a non-home compostable thermoplastic binder (PBS) was used. The resulting laminate is compostable in an industrial environment as specified in EN13432.

[0100] Sample 7 6g / m 2 A laminate was prepared as described for Sample 1, except that an amount of compostable thermoplastic binder (PLA, from Chukyo-Yushi) was used. The resulting laminate is compostable in an industrial environment as specified in EN13432.

[0101] Sample 8 CMC (Sulflex; 70 g / m 2 Laminates were prepared as described for Sample 2, except that a different support layer was used, including cellulose acetate. The resulting laminates are fully compostable in a home composter.

[0102] Sample 9 31g / m 2 Laminates were prepared as described for Sample 4, except that a different cellulosic wet-laid nonwoven base was used that did not contain CMC having a gram of 0.01 g. The resulting laminate beverage capsule lidding structure is fully compostable in a home composter.

[0103] [Table 2]

[0104] [Table 3]

[0105] [Table 4]

[0106] [Table 5]

[0107] Testing Protocol Coffee capsules must meet high material-specific requirements. During the infusion step, hot water is injected into the coffee capsule until the desired pressure value is reached. This causes the lid to deform and penetrate a static puncture element such as a pyramidal plate. This process is illustrated by figures 1A and 2B. The coffee lid must therefore withstand the pressure inside the capsule until it bursts. The inventors have devised a protocol to evaluate this performance as follows:

[0108] The tests involved preparing coffee capsules with the same physical components, the same amount of coffee, and closing the coffee capsules with different lids as described in the examples above.

[0109] The sealed coffee capsule is placed in a coffee machine (Pixie Machine) and the pressure, resulting volume and coffee flow rate during brewing are measured. The results are summarized in Table 5 below. The limits set out in Table 4 below were set.

[0110] [Table 6]

[0111] result

[0112] [Table 7]

[0113] From Table 5, it can be seen that the samples according to the present invention show the best performance. Referring to the air permeability and pore size distribution summarized in Tables 3.1 to 3.3, it can be seen that the samples according to the present invention have lower air permeability and smaller pore size than the PLA-based comparative samples.

[0114] The different samples tested can be divided into three groups. Group 1: Comparative samples 1 to 3 used a nonwoven fabric substrate having synthetic fibers.

[0115] Group 2: Samples 1, 2, 3, 6, 7, and 8, 37 g / m 2 The same cellulose wetlaid nonwoven fabric was used, containing a CMC binder with a basis weight of 100 g / m2. The cellulose wetlaid has a single layer structure as described above, i.e., does not have a two-layer or multi-layer structure. Samples 1 to 3 are impregnated with various amounts of thermoplastic binder (4, 6 and 12 g / m2 for Samples 1 to 3, respectively). 2(SciTech ST6515 from Sample 6). Samples 6 and 7 are impregnated with different thermoplastic binders (PBS for Sample 6, PLA for Sample 7). Sample 8 uses a different backing layer than that used for the other samples.

[0116] Group 3: Samples 4, 5, and 9 are cellulose wet-laid samples with a two-ply structure. They are produced using a headbox with two compartments feeding different fiber mixes. The main advantage of having two layers is the structure gradient within the paper. The fiber compositions are summarized in Table 3.3.

[0117] The samples of group 1 are found to perform in a less optimal manner. Both comparative samples 1 and 2 show (mostly) lower flow rates than the samples according to the invention. As explained in detail above, the fluid dynamics of coffee extraction from a coffee capsule are mainly influenced by the material and pore size, i.e. the permeability of the filter material. This is because the coffee used for extraction in coffee capsules under high pressure usually has a standardized degree of grinding that contains a large amount of fine particles (<100 μm). As described below, the coffee samples used in the test protocol of the invention have a particle size distribution as shown in FIG. 5, measured with a Mastersizer 3000 (Malvern).

[0118] Synthetic fibers, being man-made, tend to be uniform in size and shape. They also have a smooth surface. Without wishing to be bound by any theory, it is believed that nonwovens made exclusively from synthetic fibers tend to have a relatively uniform pore structure and tend to have larger pores compared to cellulose wet samples. Coffee particles tend not to be properly held or tend to clog the pore structure uniformly.

[0119] On the other hand, the cellulose wet sample is made of natural cellulose fibers that have a less uniform random pore structure as well as smaller pores. When using a cellulose nonwoven during coffee brewing, the liquid appears to find a path through the filter.

[0120] Differences in flow rates were observed for Samples 1, 2, and 3, which have the same cellulose nonwoven but are impregnated with various amounts of binder (see Table 5). Without wishing to be bound by any theory, the nonwoven base and the 6 g / m 2 The combination of 100% cellulose with 0.1% cellulose appears to be the optimal combination that may explain the increased flux, although all of these samples operate in the optimal range.

[0121] Furthermore, differences in pressure and flow rate are observed between samples 2, 4, 5, and 9. These differences may be explained by the different composition of the nonwoven material (base). However, these samples cannot be directly compared because nonwoven bases with different fiber mixes and structures were used.

[0122] However, the inventors have found that it is advantageous to use paper with a two-layer structure, taking into account the fine-tuning of the air permeability of the nonwoven fabric and therefore the filtration performance. In samples 4, 5, and 9, the first layer is composed of hardwood fibers that tend to be finer and therefore form a layer with low permeability. The second layer is a more permeable layer due to the softwood and artificial cellulose (i.e., rayon or lyocell) fibers used therein. Thus, these samples have good filtration performance without compromising permeability.

[0123] Furthermore, an increasing air permeability was found in the order Sample 5<Sample 4<Sample 9. In general, the higher the proportion of the first layer made only of hardwood (Sample 9<Sample 5<Sample 4), the lower the air permeability of the entire nonwoven base. However, it is believed that the addition of artificial cellulose fibers (rayon or lyocell) to the second layer may increase the air permeability of the entire nonwoven base. Furthermore, the addition of flock appears to decrease the air permeability of the samples.

[0124] Therefore, compared to the PLA based sample, the coffee lid according to the present invention with smaller pore size and lower air permeability performs better.

Claims

1. 1. A compostable filter material for liquids, comprising: the compostable filter material is a heat-sealable thermoplastic-impregnated cellulose nonwoven fabric, and the compostable filter material has a permeability of 50 to 1000 L / m at 196 Pa measured in accordance with ISO 9237 ２ Compostable filter material with a Textest air permeability of s.

2. 2. The compostable filter material of claim 1, wherein the compostable filter material has a pore size distribution including smallest pores having a smallest pore size and largest pores having a largest pore size, and wherein the average pore size of the compostable filter material is 10 to 60 μm.

3. 3. The compostable filter material of claim 2, wherein the largest pores have a maximum pore size of at least 50 μm.

4. 4. The compostable filter material of claim 3, wherein the smallest pores have a minimum pore size of 1 to 30 μm.

5. 5. The compostable filter material of any one of claims 1 to 4, wherein the heat-sealable thermoplastic-impregnated cellulosic nonwoven comprises a cellulosic nonwoven material and at least one thermoplastic binder, and the cellulosic nonwoven material comprises cellulosic fibers.

6. The amount of the thermoplastic binder is 10 to 75 wt. %, based on the total weight of the heat-sealable thermoplastic-impregnated cellulosic nonwoven fabric; and / or 6. The compostable filter material of claim 5, wherein the thermoplastic binder is a compostable binder.

7. the amount of cellulosic fibers in the cellulosic nonwoven material is 90% by weight or more, based on the total weight of the cellulosic nonwoven material; and / or the cellulosic fibers are natural or man-made cellulose fibers, or a mixture of both; and / or 7. The compostable filter material of claim 6, wherein the thermoplastic binder is one or more selected from the group consisting of polyurethane, polybutylene succinate, and polylactic acid.

8. the heat-sealable thermoplastic-impregnated cellulosic nonwoven has a basis weight of at least 15 g / m 2 ; and / or the heat-sealable thermoplastic-impregnated cellulosic nonwoven has a thickness of at least 60 μm; and / or The compostable filter material according to any one of claims 1 to 4, wherein the heat-sealable thermoplastic-impregnated cellulosic nonwoven fabric has a mean flow pore diameter of 10 to 50 μm.

9. A compostable packaging element comprising the compostable filter material of any one of claims 1 to 4.

10. A compostable packaging element as described in claim 9, which is a coffee capsule, a coffee capsule lid, or a tea bag.

11. A compostable packaging element as described in claim 10, which is a lid for a coffee capsule and comprises a cellulose support layer.

12. A method for producing a compostable filter material according to any one of claims 1 to 4, comprising the steps of: i) providing a cellulose nonwoven fabric; ii) impregnating the cellulosic nonwoven fabric with a thermoplastic binder.

13. Use of the compostable filter material according to any one of claims 1 to 4 in a method for producing a coffee drink.

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