Flame-retardant cork agglomerate and a flame-retardant adhesive paste, method of production and uses thereof

Abstract

The present disclosure relates to a flame-retardant cork agglomerate and a flame- retardant adhesive paste, method of production and uses thereof. It is disclosed a flame-retardant cork agglomerate comprising a cork agglomerate with a granulometry of size less than 2.5 mm; a pre-polymer with a dispersion of nitrogen- containing polymer particles; a flaked basalt with a granulometry of size less than 800 µm and a density lower than 0.5 g / cm3; an expandable graphite comprising a density inferior to 2 g / cm3 and an expansion lower than 700 cm3 / gr; wherein the amount of flaked basalt and expandable graphite is inferior to a 40% of the mass of the composite. It is also disclosed a flame retardant adhesive paste comprising pre-polymer with a dispersion of polymer particles containing nitrogen a expandable graphite, a flaked basalt in equal parts and liquid rheology additive.

Description

D E S C R I P T I O NFLAME-RETARDANT CORK AGGLOMERATE AND A FLAMERETARDANT ADHESIVE PASTE, METHOD OF PRODUCTION AND USES THEREOFTECHNICAL FIELD

[0001] The present disclosure relates to a flame-retardant cork agglomerate and flame-retardant adhesive paste, method of production and uses thereof.

[0002] In particular, the present disclosure relates generally to a flame resistant cork agglomerate composite, for application in the construction sector or in the railway sector, that effectively resist flames, while maintaining the physical and mechanical properties of cork as a natural and sustainable material.BACKGROUND

[0003] Flame retardant cork agglomerates are a type of material that combines cork particles with flame retardant additives to enhance the fire resistance of the cork. Cork itself is a natural and renewable material derived from the bark of cork oak trees. It is known for its lightweight, insulating, and acoustic properties, making it a popular choice for various applications, including flooring, insulation, gaskets, and more.

[0004] Flame retardant cork agglomerates are created by agglomerating or bonding cork particles together using a binder or adhesive, while also incorporating flame retardant chemicals or compounds into the mixture. The goal is to improve the material's resistance to ignition, reduce its flammability, and slow down the spread of flames in case of a fire.

[0005] In the prior art, the flame retardant additives used can vary and may include substances, such as fire-resistant chemicals, intumescent compounds, phosphorous compounds, metal oxides and hydroxides compounds, nitrogenated compounds and / or halogenated compounds. The fire-resistant chemicals release fire-inhibiting gases when exposed to high temperatures, helping to suppress the combustionprocess. The intumescent compounds swell when heated, creating a protective insulating layer that shields the underlying material from heat and flames. The phosphorous-based compounds can interfere with the combustion process and create a barrier that inhibits the spread of flames. The halogenated compounds release halogen gases when exposed to heat, which can interfere with the combustion process and reduce the material's flammability.

[0006] The resulting flame retardant cork agglomerates combine the inherent properties of cork with the fire-resistant characteristics of the additives. This makes them suitable for applications where fire safety is a critical consideration. For example, flame retardant cork agglomerates can be used in building materials, automotive components, aerospace applications, and other contexts where fire protection is essential.

[0007] However, it is important to note that while flame retardant additives can enhance the fire resistance of materials, they may also introduce environmental and health considerations. Some flame retardant compounds have been associated with potential toxicity and environmental persistence.

[0008] Furthermore, the effectiveness of flame retardant cork agglomerates in real- world fire scenarios can vary based on factors such as the type and amount of flame retardant additives used, the agglomeration process, and the overall composition of the material. Ensuring consistent and reliable fire resistance performance is a challenge. Another important point, is the environmental and health concerns, since some flame retardant additives used in materials have been associated with environmental persistence, bioaccumulation, and potential health risks. The disposal and recycling of flame retardant cork agglomerates may present challenges due to the presence of flame retardant additives. Proper waste management strategies need to be considered to minimize environmental impact.

[0009] The addition of flame retardant additives can also sometimes affect the mechanical properties of the cork agglomerates, such as their strength, flexibility, and durability. Balancing fire resistance with other functional properties is a key consideration.

[0010] Incorporating flame retardant additives and achieving uniform distribution within the cork agglomerates can also be challenging during the manufacturing process. This can impact the material's consistency and overall quality.

[0011] In the document W02020200962A1 it is disclosed a composite panel which contains or consists of at least one bio-based, particulate or rod-shaped natural substance, except wood, at least one duroplastically cured resin as a binder and at least one inorganic flame-retardant agent. The technology disclosed in such document also relates to a method for producing a corresponding composite panel and application possibilities of the composite panel.

[0012] The document US2015252187A1 discloses a multifunctional environmentally protective polyurethane composite material comprises a thermoplastic polyurethane; an environmentally protective additive including recycled polymer, plant fiber, mineral, or metal powder; and a thickening dispersant including natural rubber or synthetic rubber. By the thickening dispersant, the environmentally protective additive is uniformly added into the thermoplastic polyurethane to form the multifunctional environmentally protective polyurethane composite material. The environmentally protective additive can reduce the existing amount of waste or suppress increase of waste. With the use of the thickening dispersant and the environmentally protective additive, the multifunctional environmentally protective polyurethane composite material has advantages of light weight, good flowability, slip resistance, abrasion resistance, formability and low cost.

[0013] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0014] The present disclosure relates to a flame-retardant cork agglomerate and flame-retardant adhesive paste, method of production and uses thereof.

[0015] The flame-retardant cork agglomerate disclosed in the present disclosure comprises a cork agglomerate with a granulometry of size less than 2.5 mm, preferably from 0.25 to 2.0 mm, more preferably from 0.5 to 1.5 mm, a pre-polymer with adispersion of nitrogen-containing polymer particles, flaked basalt and expandable graphite.

[0016] The solution of the present disclosure allows an effective resistance to the flames, while maintaining the physical and mechanical properties of cork as a natural and sustainable material.

[0017] Along this description, it is considered that a nitrogen-containing polymer is a polymer rich in nitrogen atoms which, when degraded, release nitrogenous gases that suffocate the flame. As an example of nitrogen-containing polymer, it can be mentioned polyamide, polyurethane, polyurea, epoxy thermosts, melamine, and their combination thereof.

[0018] The measurement of the granulometry of cork granule may be carried out in various ways, in this disclosure the measurement granulometry / particle size was carried out on the basis of the standard the granulometry analysis by mechanical sieving, namely the one described by NP ISO 2030:2020 - Granulated cork - Size analysis by mechanical sieving. In particular concerning the sizes of the particles obtained by the sieves specified in item 4.1.2 whose openings are in accordance with series ISO / R 40 / 3 (see ISO 565:1990 - Test sieves - Metal wire cloth, perforated metal plate and electroformed sheet).

[0019] Thermal treatment, in this context, refers to subjecting the cork agglomerate to high temperatures in a controlled environment. This process involves heating the cork material to a specific temperature range, typically between 300 to 400 degrees Celsius, for a predetermined period ranging from 10-30 minutes with stirring.

[0020] Expandable graphite (also known as exfoliated graphite) is produced from the naturally occurring mineral graphite. The layered structure of graphite allows molecules to be intercalated in between the graphite layers. Through incorporation of acids, usually sulfuric acid graphite can be converted into expandable graphite.

[0021] The present disclosure relates to the field of articles or compositions comprising cork for application in various sectors, in particular in the construction sector or in the railway sector. More specifically, the present technology relates to aflame resistant cork agglomerate composite for application in the construction sector or in the railway sector.

[0022] Cork has excellent properties as a raw material, given its low conductivity to heat, sound and vibration, and its elastic capacity. Cork is also recognised for not suffering any volume change due to temperature or pressure changes. The honeycomb structure has high impact resistance and a high coefficient of friction. Thus, cork and its derivatives are considered noble materials for use and application in various industries, namely in the furniture industry, automotive industry and railway industry.

[0023] Expandable graphite is a unique form of graphite that undergoes a transformation when exposed to high temperatures, leading to an increase in volume or expansion. It is derived from natural flake graphite, which is a crystalline form of carbon with layered structures. The expansion process occurs due to the intercalation of various gases or vapors between the graphite layers, causing them to separate and push apart. In an embodiment, the expandable graphite used has an expansion coefficient of 700cm3 / gr when exposed to a temperature above 1000°C.

[0024] The safety requirements of these sectors are increasingly stringent, particularly with regard to flame resistance capacity. Thus, in recent years, cork composites comprising polyurethane resins or flame-retardant substances have been developed to increase their flame resistance. However, fire-resistant substances deteriorate the physical and mechanical properties of the materials, leading to a loss of the physical and mechanical properties that characterise cork.

[0025] The technical problem with the cork agglomerates of the prior art can, therefore, be seen as obtaining a cork agglomerate that is flame resistant and maintains the physical and mechanical properties of cork, is stable and is not harmful to the environment.

[0026] Surprisingly, the now disclosed flame-retardant cork agglomerate is able to effectively resist flames, while maintaining the physical and mechanical properties of cork as a natural and sustainable material.

[0027] Cork agglomerate usually has a flame resistance rating of E, i.e. it is considered to be a material that resists ignition by weak flame for a short period of time and doesnot produce a large spread of flame, however the composite of the present invention retains the physical and mechanical properties of cork, is non-toxic for the environment and exhibits high flame resistance, reaching Euroclass D for fire resistance. By increasing the density of the composite of the invention, we can reach Euroclass C for fire resistance.

[0028] An aspect of the disclosure comprises a flame-retardant cork agglomerate comprising a cork granulated with a granulometry of size less than 2.5 mm, a prepolymer with a dispersion of nitrogen-containing polymer particles, a flaked basalt with a particle size less than 800 pm and a density of less than 0.5 g / cm3, an expandable graphite comprising a density inferior to 2 g / cm3and an expansion lower than 700 cm3 / gr, wherein the amount of flaked basalt and expandable graphite is inferior to 40% of the mass of the composite.

[0029] In an embodiment, the flame retardant cork agglomerate comprises 38-86 % (wt / wt) of cork agglomerate, preferably 45-65 % (wt / wt); 13-44 % (wt / wt) of prepolymer; preferably 16-27 % (wt / wt); 4-18 % (wt / wt) of flaked basalt, preferably 7-11 % (wt / wt); 4-18 % (wt / wt) of expandable graphite, preferably 7-11 % (wt / wt).

[0030] In an embodiment, the cork particles used in the flame retardant cork agglomerate have a granulometry of size ranging from 0.25-2.5 mm, preferably 0.5-1.5 mm.

[0031] In an embodiment, the molecular weight of the pre-polymer used in the flame retardant cork agglomerate ranges from 1500-15000 Da; preferably 3000-8000 Da.

[0032] In an embodiment, the nitrogen-containing polymer used in the flame retardant cork agglomerate is selected from a list consisting of polyamide, polyurethane, polyurea, epoxy thermosts, melamine, silicone, acrylic, alkyd and their combination thereof, preferably polyurea.

[0033] In an embodiment, the amount of nitrogen-containing polymer particles in the pre-polymer dispersion used in the flame retardant cork agglomerate ranges from 10- 40%; preferably 15-25%.

[0034] In an embodiment, the nitrogen-containing polymer particles used in the flame retardant cork agglomerate have a granulometry of size ranging from 0.01 pm to 20 pm, preferably from 0.01 pm to 10 pm.

[0035] In an embodiment, the expandable graphite used in the flame retardant cork agglomerate have a granulometry of size ranging from 10 pm to 400 pm, preferably from 20 pm to 350 pm.

[0036] In an embodiment, the size of the flaked basalt particles used in the flame retardant cork agglomerate have a granulometry of size ranging from 10 pm to 1000 pm, preferably from 50 pm to 800 pm, more preferably from 100 pm to 740 pm.

[0037] In an embodiment, the density of the flaked basalt particles used in the flame retardant cork agglomerate ranges from 200 gr / dm3to 600 gr / dm3, preferably from 300 gr / dm3to 500 gr / dm3, more preferably from 360 gr / dm3to 430 gr / dm3.

[0038] In an embodiment, the density of the flame retardant cork agglomerate ranges from 200 gr / dm3to 600 gr / dm3, preferably from 300 gr / dm3to 500 gr / dm3.

[0039] In an embodiment, the pre-polymer used in the flame retardant is selected from a list consisting of: polyurethane, polyurea, aromatic and / or aliphatic isocyanate base, polyether polyols, ethylene oxide, propylene oxide, tetrahydrofuran, polyester polyols, polycarbonate polyols, polyols of vegetable origin and their combinations thereof, preferably polyether polyols obtained by polymerisation of an alkylene oxide (ethylene oxide, propylene oxide, tetrahydrofuran), initiated by a polyfunctional starter.

[0040] It is also described a flame retardant adhesive paste for bonding the flame retardant cork agglomerate comprising 65-95 % (wt / wt) of pre-polymer; preferably 70- 90 % (wt / wt); 5-35 % (wt / wt) of flaked basalt, preferably 7.5-15 % (wt / wt); 5-35 % (wt / wt) of expandable graphite, preferably 7.5-15 % (wt / wt); 0.5-5 % (wt / wt) of liquid rheology additive, preferably 0.5-2.5 % (wt / wt).

[0041] In an embodiment, a flame retardant polyurethane adhesive paste comprising, a polyurethane pre-polymer with a dispersion of nitrogen-containing polymer particles, a flaked basalt with a particle size of less than 800 pm and a density of less than 0. 5 g / cm3, an expandable graphite with a density of less than 2 g / cm3and anexpansion of less than 700 cm3 / g0 a liquid rheology additive, where the amount of flaked basalt and expandable graphite is less than 40% of the mass of the polyurethane pre-polymer.

[0042] In an embodiment, the liquid rheology additive used in the flame retardant adhesive paste is selected from a list consisting of: a modified formulation comprising bentonite clay base, such as Rheobyk 410 from BYK Additives, a modified formulation comprising organically modified clay, which includes a base of synthetic layered silicate modified with quaternary ammonium compounds, such as Rheobyk 7410 from BYK Additives, or their combinations.

[0043] Another aspect of the disclosure is an article comprising the flame retardant cork agglomerate now described, preferably where the article is an interior train part or an interior construction part.

[0044] Another aspect of the disclosure comprises the method for the production of the flame-retardant cork agglomerate comprising the following steps: mixing the cork granules with the pre-polymer with a dispersion of nitrogen-containing polymer particles; adding the expandable graphite so that it is well dispersed in the mixture obtained in the previous step; adding the flaked basalt so that it is well dispersed in the mixture obtained in the first step; molding the mixture obtained in the previous step for the application of temperature and pressure.

[0045] In an embodiment, the method comprises the previous step of heating the cork granules to a temperature ranging from 300 to 400°C for a period of 10 to 30 minutes with stirring.

[0046] In an embodiment, the method further comprises the step of introduction of a matrix within the cork composite.

[0047] In an embodiment, the matrix introduced though the method is selected from a list consisting of glass fibre, basalt fibre, metallic fibre, or their combinations.

[0048] In an embodiment, the method further comprises the addition of a liquid rheology additive at the same step of adding the flaked basalt for production of a flame retardant adhesive paste.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

[0050] Figure 1: Photographic representation of the results obtained for an embodiment of the flame retardant cork agglomerate subjected to a heat release test performed according to the standard ISO 11925-2:2020 (Single-flame source test).

[0051] Figure 2: Photographic representation of the results obtained for an embodiment of the flame retardant cork agglomerate subjected to a heat release test performed according to the standard ISO 11925-2:2020 (Single-flame source test).

[0052] Figure 3: Table indicating test results for homologation of an embodiment of the flame retardant cork agglomerate in an embodiment for application in a train flooring.

[0053] Figure 4: Photographic representation of the results obtained for an embodiment of the flame retardant cork agglomerate subjected to a heat release test performed according to the standard 5660-1:2015 - reaction-to-fire tests, heat release, smoke production and mass loss rate.

[0054] Figure 5: Photographic representation of degree of expansion of Expandable Graphite.

[0055] Figure 6: Table of Single Burning Item (SBI) fire reaction analysis results for the flame-retardant cork agglomerate, in accordance with standard EN 13501-1:2018 - Fire classification of construction products and building elements.

[0056] Figure 7: Table of Single Burning Item (SBI) fire reaction analysis results for flame-retardant cork agglomerate commercial without flame retardant treatment, in accordance with standard EN 13501-1:2018 - Fire classification of construction products and building elements.

[0057] Figure 8: Table of Single Burning Item (SBI) fire reaction analysis results for flame-retardant cork agglomerate, anchored to the substrate (plasterboard) with a polyurethane adhesive, in accordance with standard EN 13501-1:2018, fulfil thecriteria for classification of reaction-to-fire performance by the test method according to EN 13823:2020+Al:2022 for class "D-s2,d2".

[0058] Figure 9: Photographic representation of Single Burning Item (SBI) fire reaction of flame-retardant cork agglomerate anchored to the substrate with a flame-retardant adhesive.DETAILED DESCRIPTION

[0059] The present disclosure relates to a flame-retardant cork agglomerate and flame-retardant adhesive paste method of production and uses thereof.

[0060] The flame-retardant cork agglomerate disclosed in the present disclosure comprises a cork agglomerate of size less than 2.5 mm, preferably from 0.25 to 2.0 mm, more preferably from 0.5 to 1.5 mm, a pre-polymer with a dispersion of nitrogencontaining polymer particles, a flaked basalt with a granulometry of size less than 800 pm and a density lower than 0.5 g / cm3, an expandable graphite comprising a density inferior to 2 g / cm3and an expansion lower than 700 cm3 / gr, wherein the amount of flaked basalt and expandable graphite is inferior to a 40% of the mass of the composite.

[0061] The retardant cork agglomerate disclosed in the present disclosure is surprisingly able to effectively resist flames, while maintaining the physical and mechanical properties of cork as a natural and sustainable material.

[0062] In an embodiment, several polyurethane pre-polymers can be used for agglomerating cork, such as polyurethane, polyurea, aromatic and / or aliphatic isocyanate base, polyether polyols, ethylene oxide, propylene oxide, tetrahydrofuran, polyester polyols, polycarbonate polyols, polyols of vegetable origin and their combinations thereof, preferably polyether polyols obtained by polymerisation of an alkylene oxide (ethylene oxide, propylene oxide, tetrahydrofuran), initiated by a polyfunctional starter.

[0063] In the prior art, the film of these pre-polymers when exposed to an ignition flame burns like plastic and does not self-extinguish when the ignition flame is removed, however as used in this technology, using a pre-polymer film with nitrogen-containing polymer particles surprisingly turns the film into a self-extinguishable material when the ignition flame is removed.

[0064] In an embodiment, the cork agglomerate comprises cork granules with a grain size of 0.5 to 1.5mm, a polyurethane adhesive with 16-20% polyurea particles with a grain size of 0.01 pm to 10 pm dispersed, expandable graphite with a grain size of more than 300 pm and expansion at 1000°C of 700ml / gr, and flaked basalt with a grain size of 100 pm to 740 pm and a density of 0.36 - 0.43 gr / cm3.

[0065] In an embodiment, the cork agglomerate has a density from 200 gr / dm3to 600 gr / dm3, preferably from 300 gr / dm3to 500 gr / dm3.

[0066] In an embodiment, the polyurea particles dispersed in the adhesive used to agglomerate the flame-resistant composite act like small fire extinguishers dispersed in the composite. Polyurea particles are a polymer rich in nitrogen atoms. When exposed to temperatures above 250°C, the polymer degrades and releases gaseous compounds very rich in nitrogen that extinguish the flame by asphyxiation.

[0067] In an embodiment, the expandable graphite used has an expansion coefficient of 700cm3 / gr when exposed to a temperature above 1000°C. When the graphite expands (intumescence) it creates a barrier that hinders the progression of the flame in the composite.

[0068] In an embodiment, the flaked basalt is a fire-retardant product with a density comprised from 300 gr / dm3to 500 gr / dm3, almost the same as the composite, which means that we can use this fire-retardant product to protect our composite without increasing the final density of the composite. Graphite has a density of 1900 - 2000 gr / dm3, so we can't use large quantities of it as it increases the density of our composite considerably.

[0069] In an embodiment, the flaked basalt allows us to have a composite with a density of 300gr / dm3but with a higher compaction rate than graphite. The compaction rate of the composite is also a factor that helps to no ignite the composite.

[0070] In an embodiment obtained by the combination of polyurea particles (fire extinguishers), expandable graphite (intumescent barrier) and low-density flaked basalt as a refractory fire-retardant material, it is possible to obtain a highercompaction rate. In the experiments, it was possible to achieve a low-density 300 gr / dm3fire-resistant cork composite. It is also described a flame retardant adhesive paste for bonding the flame retardant cork agglomerate comprising 65-95 % (wt / wt) of pre-polymer; preferably 70-90 % (wt / wt); 5-35 % (wt / wt) of flaked basalt, preferably 7.5-15 % (wt / wt); 5-35 % (wt / wt) of expandable graphite, preferably 7,5-15 % (wt / wt); 0.5-5 % (wt / wt) of liquid rheology additive, preferably 0.5-2.5 % (wt / wt).

[0071] In an embodiment, a flame retardant polyurethane adhesive paste comprising, a polyurethane pre-polymer with a dispersion of nitrogen-containing polymer particles, a flaked basalt with a particle size of less than 800 pm and a density of less than 0. 5 g / cm3, an expandable graphite with a density of less than 2 g / cm3and an expansion of less than 700 cm3 / gr, a liquid rheology additive, where the amount of flaked basalt and expandable graphite is less than 40% of the mass of the polyurethane pre-polymer.

[0072] In an embodiment, the liquid rheology additive used in the flame retardant adhesive paste is selected from a list consisting of: a modified formulation comprising bentonite clay base, such as Rheobyk 410 from BYK Additives, a modified formulation comprising organically modified clay, which includes a base of synthetic layered silicate modified with quaternary ammonium compounds, such as Rheobyk 7410 from BYK Additives, or their combinations.

[0073] Another aspect of the disclosure is an article comprising the flame retardant cork agglomerate now described, preferably where the article is an interior train part or an interior construction part.

[0074] The method for the production of the flame-retardant cork agglomerate comprises the following steps: mixing the cork granules with the pre-polymer with a dispersion of nitrogen-containing polymer particles; adding the expandable graphite so that it is well dispersed in the mixture obtained in the previous step; adding the flaked basalt so that it is well dispersed in the mixture obtained in the first step; molding the mixture obtained in the previous step for the application of temperature and pressure, preferably on a temperature ranging from 110 to 130°C, a pressure that varies in function of the material volume to be compressed and the desired final density, that is considered within the range from 1000 to 2000 N.

[0075] In an embodiment, the method comprises the previous step of heating the cork granules to a temperature ranging from 300 to 400°C for a period of 10 to 30 minutes with stirring.

[0076] In an embodiment, the method further comprises the step of introduction of a matrix inside the cork composite, for improvement of the mechanical performance.

[0077] In an embodiment, the matrix introduced though the method is selected from a list consisting of glass fibre, basalt fibre, metallic fibre, or their combinations, for improvement of the mechanical performance.

[0078] In an embodiment, the method further comprises the addition of a liquid rheology additive at the same step of adding the flaked basalt for production of a flame retardant adhesive paste.

[0079] In Figure 1, it is possible to check the results on the heat release test performed according to the standard ISO 11925-2:2020 (Single-flame source test). As can be seen in Figure 1 a), test specimens for ignitability testing with the flame-retardant cork agglomerate were used. According to the ISO 11925-2:2020 (Single-flame source test), the ignitability testing is positively overcomed when the maximum height of the flame travel is lower than 150 mm - the test specimens are considered positive when the ignition flame is removed, and they immediately extinguish. As can be seen in Figure 1 b), when a flame of 20mm is applied during 15 seconds, according to ISO 11925-2:2020 - E Class, the test specimens only burn for 35 mm, which is significantly less that the test establishes for a low ignitability. As can be seen in Figure 1 c), when a flame of 20mm is applied during 30 seconds, according to ISO 11925-2:2020 - D Class, the test specimens only burn for 45 mm, which is significantly less that the test establishes for a low ignitability. Therefore, it is proved that the cork agglomerate now developed is a flame-retardant product.

[0080] In figure 2, it is possible to check the results on the heat release test performed according to the standard ISO 11925-2:2020 (Single-flame source test) - D Class. As can be seen in this figure, the cork agglomerate was subject to flame but the fire did not evolve, with a burn of just 45 mm, proving once again that the cork agglomerate now developed is a flame-retardant product.

[0081] In Figure 3, it is possible to see the test results for homologation of an embodiment of the flame retardant cork agglomerate for application in a train flooring.

[0082] In Figure 4, it is possible to check the results on the heat release test, where it is well established that the use of 10% flaked basalt significantly increased the hardness of the residual coal (refractory layer) and the energy released per m2decreases, making it more difficult for the fire to spread due to the lower energy release per square meter. This test was performed according to the standard ISO 5660-1:2015 - reaction-to-fire tests, heat release, smoke production and mass loss rate.

[0083] In Figure 5, it is represented the degree of expansion of expandable graphite when exposed to a temperature. In this case, an exposure to a temperature of 450 - 550°C using a hot air gun has been used and the initial volume increases by 4 to 5 times.

[0084] In Figure 6, it is possible to view the results of the single burning item (SBI) fire reaction analysis of flame-retardant cork agglomerate in accordance with standard EN 13501-1:2018 - Fire classification of construction products and building elements. To achieve these results, specimens with a density of 300g / dm3and a thickness of 10mm were used, without internal reinforcement with a matrix, such as glass fibre mesh, basalt fibre mesh, metal mesh, or their combinations. The specimens were also not anchored to the substrate with flame retardant adhesive. The collapse of the composite structure significantly jeopardises the results of exposure to fire, nevertheless it was possible to improve the performance of the flame retardant cork agglomerate by increasing the density of the composite, or with an internal reinforcement of the composite with a matrix, such as glass fibre mesh, basalt fibre mesh, metal mesh, or their combinations, or by bonding with flame retardant adhesives, e.g. gypsum glue, to a substrate e.g. plasterboard wall.

[0085] In Figure 7, it is possible to view the results of the single burning item (SBI) fire reaction analysis of commercial cork agglomerate, known from the prior art, without flame retardant treatment in accordance with standard EN 13501-1:2018 - Fire classification of construction products and building elements. To achieve these results, specimens with a density of 300g / dm3and a thickness of 10mm were used, withoutinternal reinforcement with a matrix, such as glass fibre mesh, basalt fibre mesh, metal mesh, or their combinations. The specimens were also not anchored to the substrate with flame retardant adhesive. Test to prove the fire resistance capacity of the cork composite.

[0086] In Figure 8, it is possible to view the results of the single burning item (SBI) fire reaction analysis of flame-retardant cork agglomerate in accordance with standard EN 13501-1:2018 - Fire classification of construction products and building elements. To achieve these results, specimens with a density of 300g / dm3 and a thickness of 10mm were used, without internal reinforcement with a matrix, such as glass fibre mesh, basalt fibre mesh, metal mesh, or their combinations. The specimens were anchored to the substrate (plasterboard) with the polyurethane adhesive of the invention, in accordance with standard EN 13501-1:2018, fulfil the criteria for classification of reaction-to-fire performance by the test method according to EN 13823:2020+Al:2022 for class "D-s2,d2".

[0087] In Figure 9, it is represented the damage caused to the cork composite of the invention when exposed to fire for 20 minutes in the test single burning item (SBI) fire reaction.

[0088] The collapse of the composite structure significantly jeopardises the results of exposure to fire, nevertheless it was possible to improve the performance of the flame retardant cork agglomerate by increasing the density of the composite, or with an internal reinforcement of the composite with a matrix, such as glass fibre mesh, basalt fibre mesh, metal mesh, or their combinations, or by bonding to the substrate (plasterboard) with a flame retardant adhesive.

[0089] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0090] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable.

[0091] The following dependent claims further set out particular embodiments of the disclosure.

Claims

C L A I M S1. Flame-retardant cork agglomerate comprising a cork agglomerate with a granulometry of size less than 2.5 mm; a pre-polymer with a dispersion of nitrogen-containing polymer particles; a flaked basalt with a particle size less than 800 pm and a density of less than 0.5 g / cm3; an expandable graphite comprising a density inferior to 2 g / cm3and an expansion lower than 700 cm3 / gr; wherein the amount of flaked basalt and expandable graphite is inferior to a 40% of the mass of the composite.

2. Flame retardant cork agglomerate according to the previous claim comprising: 38-86 % (wt / wt) of cork agglomerate, preferably 45-65 % (wt / wt);13-44 % (wt / wt) of pre-polymer; preferably 16-27 % (wt / wt);4-18 % (wt / wt) of flaked basalt, preferably 7-11 % (wt / wt);4-18 %(wt / wt) of expandable graphite, preferably 7-11 % (wt / wt).

3. Flame retardant cork agglomerate according to any of the previous claims, wherein the cork particles have a granulometry of size ranging from 0.25-2.5 mm, preferably 0.5-1.5 mm.

4. Flame retardant cork agglomerate according to any of the previous claims, wherein the molecular weight of pre-polymer ranges from 1500-15000 Da; preferably 3000-8000 Da.

5. Flame retardant cork agglomerate according to any of the previous claims, wherein the nitrogen-containing polymer is selected from a list consisting of polyamide, polyurethane, polyurea, epoxy thermosts, melamine, silicone, acrylic, alkyd, and their combination thereof; preferably polyurea.

6. Flame retardant cork agglomerate according to any of the previous claims wherein the amount of nitrogen-containing polymer particles in the pre-polymer dispersion ranges from 10-40%; preferably 15-25%.

7. Flame retardant cork agglomerate according to any of the previous claims, wherein the nitrogen-containing polymer particles have a granulometry of size ranging from 0.01 pm to 20 pm, preferably from 0.01 pm to 10 pm.

8. Flame retardant cork agglomerate according to any of the previous claims, wherein the expandable graphite comprises a granulometry of size ranging from 10 pm to 400 pm, preferably from 20 pm to 350 pm.

9. Flame retardant cork agglomerate according to any of the previous claims wherein the size of the flaked basalt particles comprises a granulometry of size ranging from 10 pm to 1000 pm, preferably from 50 pm to 800 pm, more preferably from 100 pm to 740 pm.

10. Flame retardant cork agglomerate according to any of the previous claims wherein the density of the flaked basalt particles ranges from 200 gr / dm3to 600 gr / dm3, preferably from 300 gr / dm3to 500 gr / dm3, more preferably from 360 gr / dm3to 430 gr / dm3.

11. Flame retardant cork agglomerate according to any of the previous claims, wherein the density ranges from 200 gr / dm3to 600 gr / dm3, preferably from 300 gr / dm3to 500 gr / dm3.

12. Flame retardant cork agglomerate according to any of the previous claims, wherein the pre-polymer is selected from a list consisting of: polyurethane, polyurea, aromatic and / or aliphatic isocyanate base, polyether polyols, ethylene oxide, propylene oxide, tetrahydrofuran, polyester polyols, polycarbonate polyols, polyols of vegetable origin and their combinations thereof.

13. Flame retardant adhesive paste for bonding the flame retardant cork agglomerate described in any of the previous claims, comprising:65-95 % (wt / wt) of pre-polymer; preferably 70-90 % (wt / wt);5-35 % (wt / wt) of flaked basalt, preferably 7.5-15 % (wt / wt);5-35 % (wt / wt) of expandable graphite, preferably 7.5-15 % (wt / wt);0.5-5 % (wt / wt) of liquid rheology additive, preferably 0.5-2.5 % (wt / wt).

14. Flame retardant adhesive paste according to the previous claim, wherein the liquid rheology additive is selected from a list consisting of a modified formulation comprising bentonite clay base, a modified formulation comprising organically modified clay, which includes a base of synthetic layered silicate modified with quaternary ammonium compounds, or their combinations.

15. An article comprising the flame retardant cork agglomerate described in any of the previous claims 1 to 14, preferably where the article is an interior train part or an interior construction part.

16. Method for the production of the flame-retardant cork agglomerate described in any of the previous claims 1 to 14, comprising the following steps: mixing the cork granules with the pre-polymer with a dispersion of nitrogencontaining polymer particles; adding the expandable graphite so that it is well dispersed in the mixture obtained in the previous step; adding the flaked basalt so that it is well dispersed in the mixture obtained in the first step; molding the mixture obtained in the previous step for the application of temperature and pressure.

17. Method according to the previous claim, comprising the previous step of heating the cork granules to a temperature ranging from 300 to 400°C for a period of 10 to 30 minutes with stirring.

18. Method according to any of the previous claims 16 to 17, further comprising the step of introduction of a matrix within the cork composite.

19. Method according to the previous claim, wherein the matrix is selected from a list consisting of glass fibre, basalt fibre, metallic fibre, or their combinations.

20. Method according to any of the previous claims 16 to 19, further comprising the addition of a liquid rheology additive at the same step of adding the flaked basalt for production of a flame retardant adhesive paste.

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