Composite comprising aerogel particles

Abstract

The present invention relates to a composite comprising two or more layers comprising a layer (LA) with a thickness in the range of from 0.1 to 4 mm comprising primarily aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, and one adjacent binder layer (LB) with a thickness in the range of from 0.01 to 1 mm, optionally a support layer adjacent to the binder layer (LC) with a thickness in the range of from 0.01 to 3 mm, optionally a second adjacent binder layer (LB') and support or cover layer (LC') on the second side of particle layer (LA), where aerogel particle layer (LA) comprises a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and optionally parts of support layer (LC) and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm. The present invention furthermore relates to a process for preparing said composite and the use of a composite according to the invention as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, automotive applications, infrastructure applications, marine applications, oil and gas applications or apparel, or as heat-shield material or material against thermal propagation in batteries.

Description

[0001] Composite comprising aerogel particles

[0002] The present invention relates to a comprising two or more layers comprising a layer (LA) with a thickness in the range of from 0.1 to 4 mm comprising primarily aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, and one adjacent binder layer (LB) with a thickness in the range of from 0.01 to 1 mm, optionally a support or cover layer adjacent to and on the second side of the binder layer (LB) (LC) with a thickness in the range of from 0.01 to 3 mm, optionally a second adjacent binder layer (LB’) and support or cover layer (LC’) on the second side of aerogel particle layer (LA), where aerogel particle layer (LA) comprises a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and optionally parts of support layer (LC) and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm. The present invention furthermore relates to a process for preparing said composite and the use of a composite according to the invention as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, automotive applications, infrastructure applications, marine applications, oil and gas applications or apparel, or as heat-shield material or material against thermal propagation in batteries.

[0003] Aerogel materials are known from the state of the art for their superinsulating properties. Commercial aerogel materials are used as superinsulation e.g. in construction, transportation.

[0004] Currently available commercial aerogel materials are almost exclusively based on inorganic silica aerogel in the form of aerogel fiber blankets, aerogel particles or aerogel powder. Aerogels typically require hydrophobization e.g. with silane additives to be sufficiently resistant against water and humidity in the application. Inorganic silica aerogels, especially when dried using supercritical CO2, and especially hydrophobized silica aerogels suffer from weak mechanical integrity which leads to formation and release of dust across all use phases such as shipping, installation, use and disposal. The dust release makes handling and integration of the silica aerogels difficult.

[0005] For some applications, aerogel composites or blankets of various thicknesses are required. For electrical vehicle (EV) batteries, particularly thin composites or blankets of a thickness of 2 mm or less are required. Aerogel blankets can be cut into thin layers but there is a limit to the minimum thickness set by the fiber carrier since too thin layers can lead to loss of the contained aerogel if not sufficiently well retained in the fibrous structure of the carrier. Alternatively, composites of aerogel powder can be formed by mixing and compressing with fibers. One solution of the state of the art is encapsulation of the resulting composite or blanket to avoid dust release into the area surrounding the aerogel composite, which could make its handling difficult or negatively affect the function of the overall system. Especially in case of transportation applications, the typical vibrations created during use can otherwise lead to dust formation and release. Independent of any encapsulation, the aerogel material can also be dislocated inside the blanket or composite by the vibrations, which can lead to material inhomogeneities inside the composite and impairment of its function. This is especially problematic in case of heat shields for cell-to- cell applications of electrical vehicle batteries since such an impairment of function could compromise electrical vehicle safety in case of a thermal runaway event.

[0006] For example EP0850206B1 describes aerogel composites made of aerogel particles of small diameter (<0.5 mm) and different physical or reactive binder systems. The binder and aerogel are mixed and the mixture compressed. The binder forms a continuous phase, which degrades thermal conductivity via heat bridges. EP0854892B1 describes an aerogel sheet based on a wet process which requires drying.

[0007] EP0963358B1 describes an aerogel composite based on aerogel particles compressed with thermoplastic binder in a sandwich structure. The binder and aerogel are mixed and the mixture compressed. The binder forms a continuous phase, which degrades thermal conductivity via heat bridges. WO2016053399A2 describes thin aerogel blankets based on a typical aerogel manufacturing process based on supercritical drying using thin blankets, which requires supercritical drying of the aerogel inside the blankets.

[0008] US9097377B2 describes thin aerogel composites based on thin aerogel blankets encapsulated in lamination foil layers to avoid dust release, which requires manufacturing of the aerogel blankets, cutting into thinner blankets and lamination steps.

[0009] Another disadvantage of existing aerogel materials such as silica aerogel blankets results from cost-intensive production processes. Most aerogel materials require a supercritical drying process to conserve the desired material pore structure of the wet gel stage in the dry aerogel stage. Supercritical drying requires pressure vessels and the use of a drying medium such as CO2 or ethanol in the supercritical state, which requires high pressures and temperatures. The aerogel blankets are supercritically dried in autoclaves which need to be of sufficiently large internal diameter, often more than 0.5 m or even more than 1 m and length to accommodate the rolled aerogel blankets and thus are costly to build and operate. Furthermore, increased thickness of the aerogel blankets leads to longer supercritical drying time due to diffusion limitation, and in the case of aerogel blankets with a typical thickness range of 5-20 mm the drying time is exponentially longer than for small aerogel particles of less than 3-4 mm diameter. The loading and unloading of autoclaves is more difficult in case of aerogel blankets and requires high pressure-compatible fast-opening lids while alcogel particles and aerogel particles can simply be pumped as slurry or moved using pneumatic systems. Furthermore, the silica aerogel materials disclosed in the state of the art generally are dusty.

[0010] Therefore, there is a need for aerogel materials that combine the advantage of time- and costefficient aerogel production with easy fabrication of a blanket or composite that does not release any dust in the application. According to the present invention, this object has been solved by a composite comprising two or more layers comprising

[0011] (a) a layer (LA) with a thickness in the range of from 0.1 to 4 mm comprising primarily aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, and

[0012] (b) one adjacent binder layer (LB) with a thickness in the range of from 0.01 to 1 mm

[0013] (c) optionally a support layer adjacent to and on the second side of the binder layer (LB) (LC) with a thickness in the range of from 0.01 to 3 mm,

[0014] (d) optionally a second adjacent binder layer (LB’) and support or cover layer (LC’) on the second side of particle layer (LA), where aerogel particle layer (LA) comprises a layer section (LA-1 ) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and optionally parts of support layer (LC) and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm.

[0015] Surprisingly, it was found that by tuning the formulation of aerogel particles it is possible to adjust the ductility or brittleness of said particles and to obtain ductile aerogel particles so that under compression or vibration the ductile aerogel particles do not break apart and do not release any dust. Furthermore, it was found that by arranging a close-packed layer of such ductile aerogel particles and preferably also simple compression of the aerogel particle layer, the aerogel particles form an aerogel layer suitable for thermal insulation. In combination with facings and a binder layer on both sides of the aerogel particle layer, a dust-free layered aerogel composite is obtained that does not release any dust during use or under vibration.

[0016] The thicknesses can determined for example by measuring distances in a cross-section using light microscopy or by using x-ray tomography. For measuring thicknesses below 10 pm, imaging techniques such as scanning electron microscope or micro x-ray tomography is the preferred choice. For measuring thicknesses above 10 pm, optical microscropy or also scanning electron microscopy can be used. Composites are cut into pieces in such a way as to generate cross-sections from which thicknesses of the various layers can be determined. Layers may need to be separated prior to measurement.

[0017] Measurement of the thickness of thin coatings on a surface using angled cuts and light microscopy is for example described by ASTM D 4138. Measurement of thicknesses using thickness gauges is described in ASTM D 6988.

[0018] Layer (LA) has a thickness in the range of from 0.1 to 4 mm and comprises primarily aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, and may comprise further particles. It is also possible according to the present invention that layer (LA) comprises more than 35% by volume of layer (LA) of aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, for example more than 50% by volume, or more than 60% by volume. According to the present invention, layer (LA) may also comprise aerogel particles with a different diameter or aerogel particles with different composition.

[0019] It is also possible that layer (LA) is free of further particles. It is also possible to purposefully leave empty spaces between the aerogel particles of layer (LA), or also to fill empty spaces with fillers or other materials, but layer (LA) preferably comprises more than 35% by volume of aerogel particles.

[0020] The thickness of layer (LA) may be determined by measuring the respective thickness, for example by measuring the thickness of the layer using the cross section of a respective sample. According to the present invention, the thickness may be determined by measuring several samples and using the average value obtained. For measuring the thickness of layer (LA), the distance between the upper and lower surfaces of the layer (LA) parallel to layer (LC) is measured. The respective surfaces are defined by two planes formed by the largest aerogel particles of the layer (LA) from which upper and lower boundaries of layer (LA) can be derived. The surfaces of the upper and lower planes are not flat and vary according to the aerogel particle size variation across the composite surface.

[0021] Layer (LA) is defined as the sum of two aerogel layers layer (LA-1), that contains both aerogel and binder from the binder layer (LB) and layer (LA-2), which is the aerogel layer (LA) absent of binder from the binder layer (LB).

[0022] The thickness of layer (LA-1) and (LA-2) may be determined by measuring the respective thickness, for example by measuring the thickness of the layer using the cross section of a respective sample. According to the present invention, the thickness may be determined by measuring several samples and using the average value obtained. For measuring the thickness of layer (LA-1) and (LA-2), the distance between the respective surface of the layer defined by the aerogel particles of the layer and the surface formed by the binder between the aerogel particles is measured. In case the composite comprises layers (LB) and (LB’), the thickness of layer (LA-2) is the average distance between the surfaces formed by the binder layers (LB) and (LB’) between the aerogel particles.

[0023] The binders in use in this present invention can be classified into solid binders such as thermoplastic binders or liquid binders such as thermo-setting binders. In both cases, to create adhesion, the binder is converted into an incompressible liquid (in the max compression range of this invention). In case of thermoplastic binders, the solid polymer is converted to a polymer melt upon increasing the temperature. Since the final composite is dry, the thickness of the binder should also be measured in its final form i.e. solid binder layer. This implies measuring the binder thickness after cooling in case of thermoplastic binders or after drying or curing in case of thermo-setting plastic binders. The thickness of layer (LB) may be determined by measuring the respective thickness, for example by measuring the thickness of the layer using the cross section of a respective sample. According to the present invention, the thickness may be determined by measuring several samples and using the average value obtained. For measuring the thickness of layer (LB), the distance between the upper and lower surfaces of the layer (LB) parallel to layer (LC) is measured. The respective surfaces are defined by two planes formed by the upper and lower points at a given point within the composite from which boundaries of layer (LB) can be derived. The plane surfaces can vary according to the thickness variation of layer (LB) across the composite surface. There may also be gaps in the layer (LB) e.g. if it contains fibers coated with binder.

[0024] For incompressible support layers (LC), the coating thickness of the binder layer (LB) can be determined with ISO 2808:2019 which describes procedures to determine the wet film thickness, dry film thickness and the film thickness of uncured powder layers.

[0025] The support layer thickness can be measured for example using Vernier calipers or a thickness gauge. There are various ASTM or ISO norms depending on the material of layer (LC). According to the present invention, the thickness may be determined by measuring several samples and using the average value obtained. If layer (LC) is coated with layer (LB) at the point of measurement, the thickness of (LB) is subtracted from the measured thickness to obtain the actual thickness of layer (LC). Alternatively, layers (LB) and (LA) can be removed from layer (LC) using methods known in the state of the art prior to thickness measurement.

[0026] The support layer can be compressible (thickness change upon compression) or incompressible. o determine whether the support layer (LC) is compressible, the (LC) stack is compressed with a bench press up to 5 MPa for 5 min and then the thickness is measured after removal of the compression force. If the average thickness of the support layer after compression is within 10 pm of the average thickness of the (LC) stack prior to compression, then the support layer is deemed incompressible.

[0027] Layer (LC) may consist of fibers, non-wovens or similar.

[0028] The composite according to the present invention comprises layer (LA) and layer (LB) and optionally layers (LC), (LB’), and (LC’). According to the present invention, layer (LB) is adjacent to layer (LA) and typically adheres to layer (LA). In particular, layer (LB) at least partially adheres to the aerogel particles of layer (LA), preferably to more than 60% of aerogel particles of layer (LA).

[0029] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein binder layer (LB) adheres to more than 60% of aerogel particles of layer (LA) to support layer (LC). According to the present invention, binder layer (LB) and support layer (LC) may also be combined.

[0030] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein binder layer (LB) and support layer (LC) or binder layer (LB’) and (LC’) are combined.

[0031] The aerogel particles may be organic such as based on synthetic polymers such as polyurethane, polyimide etc. or inorganic such as based on silica or hybrids of two or more polymers or systems. Suitable aerogel particles and processes for their preparation are in principle known to the person skilled in the art.

[0032] Aerogels may be hydrophobized or coated to give water repellency and humidity resistance. Coating may also impart function to the aerogels. The coating may incorporate binder. An example of coating of aerogel substrates is illustrated in the following publication https: / / doi.Org / 10.1007 / sl 0570-021 -04032-0

[0033] To improve water resistance and humidity resistance the final composites can be hydrophobized with hydrophobization agents known in the state of the art such as silanes such as TMCS, HMDSO or HMDZ, preferably in the gas phase.

[0034] The aerogel particle size depends on the final desired composite thickness in combination with the facing thickness and the desired aerogel content in the layered composite and the level of compression. Smaller aerogel particles are faster to produce while very small aerogel particles may pose explosion hazards during production and handling in case of predominantly organic aerogels or may be difficult to handle. Preferably, the aerogel particle size is <4 mm, <3 mm, <2 mm, <1 mm and larger than 0.1 mm, preferably larger than 0.5 mm and more preferably larger than 1 mm. Small aerogel particles may be produced directly or by milling or grinding of larger aerogel particles. A mixture of two or more particle sizes may be employed to replace the gaps of air between spherical particles of a given size with smaller particles fitting into the air gap directly or after a compression step. In this way, the aerogel particle layer may be substantially air-gap free while still not containing aerogel powder with a particle size of less than 0.1 mm that may lead to release of dust from the composite.

[0035] The aerogel particle density depends on the desired aerogel properties and is typically set by the specific formulation. Ductile aerogel particles are obtained with organic polymers including biopolymers and with hybrids of organic polymers including biopolymers and inorganic precursors such as reported by PCT / EP2023 / 955870. For green composites, bio-based polymers are chosen. For fire- and high-temperature-resistant composites, a high degree of inorganic content is chosen while avoiding brittleness and dust formation. According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the uncompressed aerogel particles of layer (LA) have one or more of features (a) to (y)

[0036] (a) 80 - 99.6% porosity,

[0037] (P) 15 - 200 kg / m3particle bulk density,

[0038] (y) 16 - 30 mW / mK thermal conductivity measured at 10 °C of a loose filled particle bed.

[0039] It has been found that the aerogel particles used allow for the preparation of composites with advantageous properties. The aerogel particles can be compressed and stable composite materials can be obtained. Therefore, according to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the individual aerogel particles can be compressed to 5 - 98% of original thickness without visible breakage of the aerogel particle during compression with a compression rate from 0.01 to 5 mm / sec, or present less than 1 N drop in force due to primary breakage during compression.

[0040] Stable composites can be obtained from the aerogel particles. It has been found that particularly stable composites can be obtained when using aerogel particles having a diameter of the uncompressed aerogel particles in the range of from 0.1 to 4 mm. Preferably, the aerogel particle size distribution is monodisperse or polydisperse or partially monodisperse, and preferably sphericity of the individual aerogel particle ranges from 25% to 100%.

[0041] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein,

[0042] (I) the aerogel particle size distribution is monodisperse or polydisperse or partially monodisperse, and / or

[0043] (II) sphericity of the individual aerogel particle ranges from 25% to 100%.

[0044] According to the present invention, it has been found that in particular silica based aerogels have good properties for the preparation of composites. Preferably, the aerogel is a silica-based aerogel.

[0045] In particular, hybrid aerogels comprising a biopolymer selected from ionically crosslinkable polycarboxylate polymer, alginate, pectin or modified cellulose.

[0046] The polarity of the aerogel may also be adjusted by further treatment steps of the aerogel as such. Suitable treatments such as for example hydrophobization steps are in principle known.

[0047] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the aerogel is a silica-based aerogel comprising (A) 20-80% silica by mass and 20% of ionically crosslinkable polycarboxylate polymer but at least 25 kg / m3ionically crosslinkable polycarboxylate polymer, or

[0048] (B) 20-90% silica by mass and 10% alginate by mass but at least 15 kg / m3alginate, or

[0049] (C) 20-85% silica by mass and 15% pectin by mass but at least 20 kg / m3pectin, or

[0050] (D) 20-80% silica by mass and 20% CMC by mass but at least 25 kg / m3CMC, or

[0051] (E) 20-85% silica by mass and 7.5% alginate by mass and at least 15 kg / m3alginate and at least 10 kg / m3of non-alginate ionically crosslinkable polycarboxylate polymer.

[0052] The aerogel particles may also contain further materials to adjust the properties of the materials such as for example lignin, tannin, polysaccharides, proteins, synthetic polymers, fillers, opacifiers or materials providing high-temperature stability or fire resistance or elasticity. According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the aerogel particles contain lignin, tannin, polysaccharides, proteins, synthetic polymers, fillers, opacifiers or materials providing high-temperature stability or fire resistance or elasticity.

[0053] Binders may be required to bond aerogel particles to the facings or the aerogel particles to each other as long as there is a layer (LA-2) that is free of binder to avoid negative impact of the binder on the thermal insulation performance of the composite. The binder should not enter the aerogel layer beyond the depth set by layer (LA-1 ) but at least layer (LA-2) needs to be free of binder forming thermal bridges. Reactive binders such as acrylate, polyurethane, epoxy, silicone or thermoplastic binders such as PE, PP, PA, TPU, silicone and others are possible. For green composites bio-based binders are chosen. The binders may be in the form of a liquid formulation, a powder, a sheet, a non-woven, fibers or other suitable geometries. The binder formulation needs to be chosen in such a way as to avoid penetration and damage to the aerogel particle pores and loss of insulation performance for example by using water-based binder formulations and water-repelling aerogel particles or highly viscous binder formulations. The binders need to show good binding to the aerogel particles and any facings to achieve mechanical integrity of the layered composite and to avoid unwanted detachment or release of aerogel particles from the composite. At the same time the binder layer should be as thin as possible to avoid negative impact on the thermal insulation performance of the composite. The binders need to be chosen based on the operating temperature of the application for example thermoplastic binders with a sufficiently high melting temperature need to be used. The temperature should not be so high as to damage the aerogel particles or facings. Such binders are known in the state of the art.

[0054] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein herein the binder is selected from reactive binders based on acrylates, polyurethanes, epoxy resins, silicone or water glass or other inorganic binder systems, or from thermoplastic binders based on PE, PP, PA, TPU, PLA or other bio-based polymers, silicone, or on mixtures of any of those binders. For manufacturing of the layered aerogel particle composites, it is possible to first form the binder and facing layers and subsequently add the aerogel particles for binding instead of mixing or coating aerogel particles with binder.

[0055] In the context of the present invention, it is also possible to use a binder as such or a binder composition comprising a binder and suitable additives such as for example fillers, in particular fibrous fillers or fire-resistant fillers.

[0056] Surprisingly, it was found that by tuning the formulation of the aerogel particles, it is possible to obtain fire-resistant ductile aerogel particles that do not lead to dust release. From such fire-resistant ductile aerogel particles fire-resistant layered aerogel composites can be formed that are dust-free.

[0057] The aerogel particle composites can be produced from the aerogel particles in a discontinuous or continuous process. In principle, a cost-efficient and fast roll-to-roll process is possible.

[0058] The facings may be non-wovens, textiles or sheets and are in principle known from the state of the art. The facings may consist of or incorporate textiles or non-wovens, glass fiber, ceramic fiber, mica, cellulose, hemp, paper or coated paper and other bio-based materials, synthetic polymer, biopolymer. For green composites, bio-based materials are chosen. To obtain thin facings with a high relative aerogel content within the composite or a flexible composite thin facings are advantageous such as facings with a thickness of less than 2 mm, preferably less than 1 mm, more preferable less than 0.5 mm, in particular less than 0.1 mm.

[0059] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the composite contains an elastic non-woven or blanket, elastic particles, or an elastic frame surrounding aerogel layer (LA) providing elasticity to the composite when compressed mechanically.

[0060] When based on thermoplastic binder layers, layered aerogel particle composites can be made temporarily flexible by applying heat.

[0061] For manufacturing of the aerogel particle composite compression may be required to improve binding between aerogel particle layers and binder layers and facings or to reduce air gaps between aerogel particles or to reduce composite thickness. Preferably, the aerogel particles are not compressed by more than 80%, more preferably 50% to not increase the density excessively which may negatively impact thermal insulation performance.

[0062] It was found that the thermal conductivity of the aerogel particle bed was in a similar range as that of the composite, for example the lambda value will not change by more than 5 mW / m*K, preferably 2 mW / m‘K. The lambda value of such a composite will depend on the lambda value of the aerogel particles and the relative thicknesses of the aerogel particle layer compared to the binder and facing layers, but it is to be expected to be less than 30 mW / m*K, preferably less than 25 mW / m‘K, more preferably less than 23 mW / m*K.

[0063] Multiple compressed aerogel particle layers can be stacked to form thicker aerogel composites. The aerogel particle layers can be joined together by use of binders known in the state of the art or by sewing textile facings together as is also known in the state of the art. It is also possible to arrange multiple layers of aerogel particles on top of each other and compressing the multi-layer aerogel particle arrangement into a thicker aerogel composite. Binders may be required to bond the particles in such a multi-layer aerogel particle arrangement to each other or the aerogel particles to the facings. It is also possible to form a multi-layer arrangement of different types of aerogel particles or to fabricate mixed layers such as organic / organic, synthetic polymer / biopol- ymer, organic / inorganic, inorganic / inorganic or order to achieve certain properties of the aerogel composite.

[0064] Additionally, other types of layers or facings may be introduced to impart additional functions to the aerogel particle composites such as electrically insulating layers, heat-conducting layers, phase-change materials, layers resistant to mechanical impingement, water-barrier or fire-resistant layers.

[0065] It is possible to introduce elastic layers to impart elastic behavior to the composite. This may be advantageous for batteries of electrical vehicles to compensate for the battery cell expansion and shrinkage during operation and over the battery lifetime. One or several binder layers may be elastic for example through the use of thermoplastic elastomer or elastomer sheets, webs, powders, shaped geometries, particles and similar for example TPU. It is also possible to introduce elastic particles or shaped geometries into the aerogel particle layer (LA) for example elastomer beads, 3D-printed parts or molded parts. It is also possible to integrate smaller elastic particles into the aerogel particles of layer (LA) during the manufacturing process in the gelation step to increase and tune their elasticity. It is also possible to modify the elastic behavior of the aerogel particles through variation of the biopolymer content and type.

[0066] Typically, the composite according to the present invention has a thickness in the range of from 0.1 to 20 mm, for example in the range of from 0.2 to 15 mm, preferably in the range of from 0.3 to 10 mm or from 0.5 to 5 mm.

[0067] Typically, layers (LA) and (LB) represent at least 20% of the composite, preferably at least 30%, in particular at least 50% of the composite. In case the composite comprises multiple layers (LA) and / or (LB), the respective sum of layers (LA) and (LB) typically represents at least 20% of the composite, preferably at least 30%, in particular at least 50% of the composite

[0068] Suitable processes for preparing aerogel powder or aerogel beads are in principle known to the person skilled in the art. Suitable processes may for example comprise the preparation of a gel, solvent exchange and drying steps.

[0069] According to a further embodiment, the present invention is also directed to the method for preparing a composite as disclosed above, wherein where the aerogel beads are obtained by solvent exchange and supercritical drying or freeze drying.

[0070] The production of the aerogel particles avoids cost- and time-intensive supercritical drying of silica aerogel blankets. Supercritical drying of aerogel particles is in principle known and can be carried out in tubes of smaller diameters which can serve as autoclaves for the aerogel particles as opposed to larger and more costly autoclaves for silica aerogel blankets.

[0071] Suitable processes for preparing aerogel particle gel precursors are in principle known to the person skilled in the art. Suitable processes might include ionic crosslinking or pH-induced crosslinking.

[0072] According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the aerogel particles are prepared via ionic crosslinking or pH-induced crosslinking.

[0073] Typically a gel is formed from the components of a mixture (M 1 ) and at least one polyvalent metal ion. Mixture (M 1) comprises components which are suitable to allow the formation of a gel with the polyvalent metal ion, in particular have to have suitable functional groups.

[0074] Typically, mixture (M1 ) is brought into contact with an aqueous solution of a polyvalent metal ion to prepare a gel (A). Suitable mixing steps are in principle known to the person skilled in the art. It is for example possible to add mixture (M1 ) dropwise to the aqueous solution of the polyvalent metal ion to prepare spherical aerogel particles. It is also possible that mixture (M1 ) is provided in the pores of a carrier material or in admixture with fibers before bringing it into contact with the aqueous solution of a polyvalent metal ion to prepare a gel (A). Also, mixture (M1) can be brought into contact with the polyvalent metal ion in an emulsion or in a spray process.

[0075] Gelling is known per se to a person skilled in the art and is described, for example, in WO 2009 / 027310 on page 21 , line 19 to page 23, line 13.

[0076] Preferably, the conditions are adjusted and the hydrogel, alcogel and / or aerogel exhibit a round shape. Preferably, according to step b), a round bead with an average diameter in the range of from 0.1 to 4 mm, preferably 1 to 2 mm is obtained.

[0077] Preferably, no crosslinking or hydrophobization via covalent chemical reaction occurs. Preferably, temperature and pressure in the gelation step are adjusted to conditions under which a gel is formed. A suitable temperature might be in the range of from 5 to 40 °C, preferable in the range of from 15 to 35 °C. According to a further embodiment, the present invention also relates to a process as described above, wherein step b) is carried out at a temperature in the range of from 5 to 40 °C.

[0078] The rate of formation of the insoluble gel can be controlled very exactly and easily by choosing suitable conditions.

[0079] Gel (A) typically is a gel comprising water, i.e. a hydrogel. Usually, gel (A) is exposed to a water- miscible solvent (L) to obtain a gel (B), i.e. an organogel.

[0080] In the context of the present invention, water-miscible means that the solvent is at least partially miscible with water in order to allow an exchange of solvent in the gel.

[0081] Solvent exchange is carried out either by soaking the gel directly in the new solvent (one-step) or by following a sequential soaking (multi-step) in different water-to-new solvent mixtures with increasing content in the new solvent after a certain time (exchange frequency) in the previous soaking step (Robitzer et al., 2008, Langmuir, 24(21), 12547-12552). The solvent chosen for water replacement must satisfy the requirements of not dissolving the gel structure, being completely soluble with the solvent which precedes them (water) and preferably also accepted for manufacturing of pharmaceuticals. Furthermore, in case the process encompasses a step of supercritical drying, solvent (L) preferably is at least partially miscible with the supercritical medium.

[0082] The solvent (L) can in principle be any suitable compound or mixture of a plurality of compounds, which meets the above requirements with the solvent (L) being liquid under the temperature and pressure conditions of the process used.

[0083] Possible solvents (L) are, for example, alcohols, ketones, aldehydes, alkyl alkanoates, organic carbonates, amides such as formamide and N-methylpyrollidone, sulfoxides such as dimethyl sulfoxide, aliphatic and cycloaliphatic halogenated or non-halogenated hydrocarbons, halogenated or non-halogenated aromatic compounds and fluorine-containing ethers. Mixtures of two or more of the abovementioned compounds are likewise possible.

[0084] In many cases, particularly suitable solvents (L) are obtained by using two or more completely miscible compounds selected from the above mentioned solvents.

[0085] Suitable solvents are in particular alcohols and ketones, for example C1 to C6 alcohols and C1 to C6 ketones and mixtures thereof.

[0086] Particularly suitable are alcohols such as methanol, ethanol and isopropanol and ketones such as acetone, and methyl ethyl ketone. The solvent exchange might be carried out in one step, 2 steps, 3 steps or in multiple steps with varying concentration of the solvent. According to a preferred embodiment, gels (A) are successively immersed in ethanol / water mixtures with concentrations of fer example 30, 60, 90 and 100 wt% for 5 min to 12 h in each depending on the particle size and porosity. The solvent exchange might also be carried out continuously.

[0087] By solvent exchange, gel (B) is obtained which is then dried.

[0088] Drying typically takes place in a known manner. Drying under supercritical conditions is preferred, preferably after replacement of the solvent by CO2 or other solvents suitable for the purposes of supercritical drying. Such drying is known per se to a person skilled in the art. Supercritical conditions characterize a temperature and a pressure at which CO2 or any solvent used for removal of the gelation solvent is present in the supercritical state. In this way, shrinkage of the gel body on removal of the solvent can be reduced.

[0089] It is also possible to dry the gels obtained by conversion of the liquid comprised in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid comprised in the gel.

[0090] Preferably, the drying of the gel obtained is preferably carried out by converting the solvent (L) into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the solvent (L). Accordingly, drying is preferably carried out by removing the solvent (L) which was present in the reaction without prior replacement by a further solvent.

[0091] Such methods are likewise known to those skilled in the art and are described in WO 2009 / 027310 on page 26, line 22 to page 28, line 36.

[0092] Drying may be carried out by converting the liquid comprised in the gel into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid comprised in the gel. It is also possible that the drying is carried out under supercritical conditions.

[0093] The process might also comprise one or more further modification steps such as a shaping step that may include fibers and / or adhesives and / or thermoplastic materials, a compression step, a lamination step, a hydrophobization step, or a carbonization step. It is for example possible to combine one or more of these steps, for example a post-drying and a hydrophobization step.

[0094] According to the present invention, it has been found that in particular hybrid aerogels have good properties for the preparation of composites according to the present invention. In particular, hybrid aerogels comprising a secondary material and a biopolymer selected from ionically crosslinkable polycarboxylate polymer, alginate, pectin or modified cellulose are suitable. Suitable processes for preparing aerogels based on biopolymers are in principle known to the person skilled in the art. Typically, the aerogels are obtained by processes including formation of a gel, solvent exchange and drying. According to a further embodiment, the present invention is also directed to the liquid or pasty composition as disclosed above, wherein the aerogel beads are obtained by solvent exchange and supercritical drying or freeze drying.

[0095] Suitable aerogels might for example be prepared by a process at least comprising the steps of: a) providing a mixture (M 1 ) comprising at least one compound (C1) selected from water-soluble biopolymers and inorganic precursors, and at least one water-soluble polysaccharide with carboxylic acid groups as component (C2) and water, b) bringing mixture (M 1 ) into contact with an aqueous solution of a polyvalent metal ion to prepare a gel (A) c) exposing the gel (A) obtained in step b) to a water miscible solvent (L) to obtain a gel (B), d) drying of the gel (B) obtained in step c).

[0096] Suitable inorganic precursors in the context of the present invention have to be soluble or at least partially soluble in the mixture (M 1 ) and have to solidify in the gelation step.

[0097] For the purposes of the present invention, a gel is a crosslinked system based on a polymer which is present in contact with a liquid (known as solvogel or lyogel), or with water as liquid (aquagel or hydrogel). Here, the polymer phase forms a continuous three-dimensional network.

[0098] In the context of the present invention, water-soluble means that the solubility in water is sufficient to form a solution which can be used for preparing a gel. In the context of the present invention, also aqueous swollen dispersions may be used for the preparation of a gel.

[0099] Properties of the aerogels can be customized by adjusting the composition of mixture (M1), the reaction conditions at the stage of the formation of the hydrogel (gel (A)), or during solvent exchange as well as in the drying step. According to the present invention, it is possible to influence the properties of the hydrogels and / or aerogels by varying the ratio of the components, as well as by controlling the parameters of step b) and also by introducing a wide range of organic and inorganic materials in the gel matrix.

[0100] According to a further aspect, the present invention is also directed to a process for preparing a composite comprising two or more layers comprising the steps of

[0101] (i) forming a binder layer (LB),

[0102] (ii) forming a layer comprising primarily aerogel particles (LA), (iii) forming a composite comprising layers (LA) and (LB) by applying condition suitable to achieve stable bonding between layers (LA) and (LB), wherein the uncompressed aerogel particles of layer (LA) preferably have one or more of features (a) to (y)

[0103] (a) 80 - 99.6% porosity

[0104] (P) 15 - 200 kg / m3particle bulk density

[0105] (Y) 16 - 30 mW / mK thermal conductivity measured at 10°C of a loose filled particle bed.

[0106] In particular, the present invention is diected to a process for preparing a composite comprising two or more layers comprising the steps of

[0107] (i) forming a binder layer (LB),

[0108] (II) forming a layer comprising aerogel particles (LA) with a diameter in the range of from 0.1 to 4 mm before any compression,

[0109] (iii) forming a composite comprising layers (LA) and (LB) by applying condition suitable to achieve stable bonding between layers (LA) and (LB) and formation of a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm, wherein the uncompressed aerogel particles of layer (LA) preferably have one or more of features (a) to (Y)

[0110] (a) 80 - 99.6% porosity;

[0111] (P) 15 - 200 kg / m3particle bulk density;

[0112] (Y) 16 - 30 mW / mK thermal conductivity measured at 10°C of a loose filled particle bed.

[0113] The process of the invention comprises steps (i), (ii), and (iii) but may comprise further steps.

[0114] With respect to the preferred aerogel particles used. Reference is made to the disclosure above.

[0115] According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the aerogel is a silica-based aerogel.

[0116] According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the aerogel is a silica-based aerogel comprising

[0117] (A) 20-80% silica by mass and 20% of ionically crosslinkable polycarboxylate polymer but at least 25 kg / m3ionically crosslinkable polycarboxylate polymer, or

[0118] (B) 20-90% silica by mass and 10% alginate by mass but at least 15 kg / m3alginate, or

[0119] (C) 20-85% silica by mass and 15% pectin by mass but at least 20 kg / m3pectin, or

[0120] (D) 20-80% silica by mass and 20% CMC by mass but at least 25 kg / m3CMC, or (E) 20-85% silica by mass and 7.5% alginate by mass and at least 15 kg / m3alginate and at least 10 kg / m3of non-alginate ionically crosslinkable polycarboxylate polymer.

[0121] It has been found that particularly stable composites may be obtained by applying pressure to the composite. According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the process comprises the steps of

[0122] (iv) compressing the composite such that the aerogel is compressed to 5 - 98% of original thickness,

[0123] (v) preferably applying a compression rate in the range between 0.01 - 1 mm / sec.

[0124] The composite may also comprise further layers, such as coating layers or also further layers comprising aerogel particles. According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein further layers comprising aerogel particles are formed as part of the composite.

[0125] Also, with respect to preferred embodiments of the composite, reference is made to the disclosure above. According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the thickness of the composite is in the range of 0.1 to 20 mm.

[0126] According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the thickness of the layer (LA) comprising aerogel particles is in the range of from 0.1 to 4 mm.

[0127] According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the diameter of the uncompressed aerogel particles is in the range of from 0.1 to 4 mm.

[0128] According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the binder is selected from acrylates, polyurethanes, epoxy resins, silicone or thermoplastic binders such as PE, PP, PA, TPU, PLA.

[0129] According to a further aspect, the present invention is also directed to a composite obtained according to the process as disclosed above.

[0130] It has been found that the composites have good stability and good insulating properties which make them suitable for the use as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, oil and gas applications or apparel, or as heatshield material or material against thermal propagation in batteries. According to a further aspect, the present invention is also directed to the use of a composite as disclosed above as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, automotive applications, infrastructure applications, marine applications, oil and gas applications or apparel, or as heat-shield material or material against thermal propagation in batteries.

[0131] Preferred embodiments may be found in the claims and the description. Combinations of preferred embodiments do not go outside the scope of the present invention. Preferred embodiments of the components used are described below.

[0132] The present invention includes the following embodiments, wherein these include the specific combinations of embodiments as indicated by the respective interdependencies defined therein.

[0133] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The composite of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The composite of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0134] 1 . A composite comprising two or more layers comprising:

[0135] (a) a layer (LA) with a thickness in the range of from 0.1 to 4 mm comprising aerogel particles, with a diameter in the range of from 0.1 to 4 mm before any compression, and

[0136] (b) one adjacent binder layer (LB) with a thickness in the range of from 0.01 to 1 mm

[0137] (c) optionally a support layer adjacent to the binder layer (LC) with a thickness in the range of from 0.01 to 3 mm,

[0138] (d) optionally a second adjacent binder layer (LB’) and support or cover layer (LC’) on the second side of particle layer (LA), where aerogel particle layer (LA) comprises a layer section (LA-1 ) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and optionally parts of support layer (LC) and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm.

[0139] 2. The composite according to embodiment 1 , where binder layer (LB) adheres to more than 60% of aerogel particles of layer (LA) to support layer (LC). 3. The composite according to embodiment 1 or 2, where binder layer (LB) and support layer (LC) or binder layer (LB’) and (LC’) are combined.

[0140] 4. The composite according to any one of embodiments 1 to 3, wherein the uncompressed aerogel particles of layer (LA) have one or more of features (a) to (y)

[0141] (a) 80 - 99.6% porosity,

[0142] (P) 15 - 200 kg / m3particle bulk density,

[0143] (y) 16 - 30 mW / mK thermal conductivity measured at 10 °C of a loose filled particle bed.

[0144] 5. The composite according to any one of embodiments 1 to 4, where the individual aerogel particles can be compressed to 5 - 98% of original thickness without visible breakage of the aerogel particle during compression with a compression rate from 0.01 to 5 mm / sec, or present less than 1 N drop in force due to primary breakage during compression.

[0145] 6. The composite according to any one of embodiments 1 to 5, wherein,

[0146] (I) the aerogel particle size distribution is monodisperse or polydisperse or partially monodisperse, and / or

[0147] (II) sphericity of the individual aerogel particle ranges from 25% to 100%.

[0148] 7. The composite according to any one of embodiments 1 to 6, wherein the aerogel is a silica-based aerogel, preferably wherein the aerogel is a silica-based aerogel comprising

[0149] (A) 20-80% silica by mass and 20% of ionically crosslinkable polycarboxylate polymer but at least 25 kg / m3ionically crosslinkable polycarboxylate polymer, or

[0150] (B) 20-90% silica by mass and 10% alginate by mass but at least 15 kg / m3alginate, or

[0151] (C) 20-85% silica by mass and 15% pectin by mass but at least 20 kg / m3pectin, or

[0152] (D) 20-80% silica by mass and 20% CMC by mass but at least 25 kg / m3CMC, or

[0153] (E) 20-85% silica by mass and 7.5% alginate by mass and at least 15 kg / m3alginate and at least 10 kg / m3of non-alginate ionically crosslinkable polycarboxylate polymer.

[0154] 8. The composite according to any one of embodiments 1 to 7, wherein the aerogel particles contain lignin, tannin, polysaccharides, proteins, synthetic polymers, fillers, opacifiers or materials providing high-temperature stability or fire resistance or elasticity.

[0155] 9. The composite according to any one of embodiments 1 to 8, wherein the aerogel particles are prepared via ionic crosslinking or pH-induced crosslinking. The composite according to any one of embodiments 1 to 9, wherein herein the binder is selected from reactive binders based on acrylates, polyurethanes, epoxy resins, silicone or water glass or other inorganic binder systems, or from thermoplastic binders based on PE, PP, PA, TPU, PLA or other bio-based polymers, silicone, or on mixtures of any of those binders. The composite according to any one of embodiments 1 to 10, wherein the composite contains an elastic non-woven or blanket, elastic particles, elastic shapes or an elastic frame surrounding aerogel layer (LA) providing elasticity to the composite when compressed mechanically. Process for preparing a composite comprising two or more layers comprising the steps of (i) forming a binder layer (LB),

[0156] (II) forming a layer comprising aerogel particles (LA) with a diameter in the range of from 0.1 to 4 mm before any compression,

[0157] (iii) forming a composite comprising layers (LA) and (LB) by applying condition suitable to achieve stable bonding between layers (LA) and (LB), wherein the uncompressed aerogel particles of layer (LA) have one or more of features (a ) to (y)

[0158] (a) 80 - 99.6% porosity

[0159] (P) 15 - 200 kg / m3particle bulk density

[0160] (Y) 16 - 30 mW / mK thermal conductivity measured at 10°C of a loose filled particle bed. Process for preparing a composite comprising two or more layers comprising the steps of (i) forming a binder layer (LB),

[0161] (II) forming a layer comprising aerogel particles (LA) with a diameter in the range of from 0.1 to 4 mm before any compression,

[0162] (iii) forming a composite comprising layers (LA) and (LB) by applying condition suitable to achieve stable bonding between layers (LA) and (LB) and formation of a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm, wherein the uncompressed aerogel particles of layer (LA) preferably have one or more of features (a) to (Y)

[0163] (a) 80 - 99.6% porosity;

[0164] (P) 15 - 200 kg / m3particle bulk density;

[0165] (Y) 16 - 30 mW / mK thermal conductivity measured at 10°C of a loose filled particle bed. The process according to embodiment 12 or 13, wherein the aerogel is a silica-based aerogel. 15. The process according to any one of embodiment 12 to 14, wherein the aerogel is a silica-based aerogel comprising

[0166] (A) 20-80% silica by mass and 20% of ionically crosslinkable polycarboxylate polymer but at least 25 kg / m3ionically crosslinkable polycarboxylate polymer, or

[0167] (B) 20-90% silica by mass and 10% alginate by mass but at least 15 kg / m3alginate, or

[0168] (C) 20-85% silica by mass and 15% pectin by mass but at least 20 kg / m3pectin, or

[0169] (D) 20-80% silica by mass and 20% CMC by mass but at least 25 kg / m3CMC, or

[0170] (E) 20-85% silica by mass and 7.5% alginate by mass and at least 15 kg / m3alginate and at least 10 kg / m3of non-alginate ionically crosslinkable polycarboxylate polymer.

[0171] 16. The process according to any one of embodiments 12 to 15, wherein the process comprises the step of

[0172] (iv) compressing the composite such that the aerogel is compressed to 5 - 98% of original thickness.

[0173] 17. The process according to any one of embodiments 12 to 16, wherein the process comprises the steps of

[0174] (iv) compressing the composite such that the aerogel is compressed to 5 - 98% of original thickness,

[0175] (v) applying a compression rate in the range between 0.01 - 1 mm / sec.

[0176] 18. The process according to any one of embodiments 12 to 17, wherein further layers comprising aerogel particles are formed as part of the composite.

[0177] 19. The process according to any one of embodiments 12 to 18, wherein the thickness of the composite is in the range of 0.1 to 20 mm.

[0178] 20. The process according to any one of embodiments 12 to 19, wherein the thickness of the layer (LA) comprising aerogel particles is in the range of from 0.1 to 4 mm.

[0179] 21 . The process according to any one of embodiments 12 to 20, wherein the binder is selected from acrylates, polyurethanes, epoxy resins, silicone or thermoplastic binders such as PE, PP, PA, TPU PLA.

[0180] 22. The process according to any one of embodiments 12 to 21 , wherein the binder layer (LB) has a thickness in the range of from 0.01 to 1 mm. 23. The process according to any one of embodiments 12 to 22, wherein the composit comprises a support layer adjacent to the binder layer (LC) with a thickness in the range of from 0.01 to 3 mm.

[0181] 24. The process according to any one of embodiments 12 to 23, wherein aerogel particle layer (LA) comprises a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and optionally parts of support layer (LC) and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm.

[0182] 25. The process according to any one of embodiments 12 to 24, wherein binder layer (LB) adheres to more than 60% of aerogel particles of layer (LA) to support layer (LC).

[0183] 26. The process according to any one of embodiments 12 to 25, where binder layer (LB) and support layer (LC) or binder layer (LB’) and (LC’) are combined.

[0184] 27. The process according to any one of embodiments 12 to 26, wherein the uncompressed aerogel particles of layer (LA) have one or more of features (a) to (y)

[0185] (a) 80 - 99.6% porosity,

[0186] (P) 15 - 200 kg / m3particle bulk density,

[0187] (y) 16 - 30 mW / mK thermal conductivity measured at 10 °C of a loose filled particle bed.

[0188] 28. The process according to any one of embodiments 12 to 27, where the individual aerogel particles can be compressed to 5 - 98% of original thickness without visible breakage of the aerogel particle during compression with a compression rate from 0.01 to 5 mm / sec, or present less than 1 N drop in force due to primary breakage during compression.

[0189] 29. The process according to any one of embodiments 12 to 28, wherein,

[0190] (I) the aerogel particle size distribution is monodisperse or polydisperse or partially monodisperse, and / or

[0191] (II) sphericity of the individual aerogel particle ranges from 25% to 100%.

[0192] 30. The process according to any one of embodiments 12 to 29, wherein the aerogel particles contain lignin, tannin, polysaccharides, proteins, synthetic polymers, fillers, opacifiers or materials providing high-temperature stability or fire resistance or elasticity. 31 . The process according to any one of embodiments 12 to 30, wherein the aerogel particles are prepared via ionic crosslinking or pH-induced crosslinking.

[0193] 32. The process according to any one of embodiments 12 to 31 , wherein herein the binder is selected from reactive binders based on acrylates, polyurethanes, epoxy resins, silicone or water glass or other inorganic binder systems, or from thermoplastic binders based on PE, PP, PA, TPU, PLA or other bio-based polymers, silicone, or on mixtures of any of those binders.

[0194] 33. The process according to any one of embodiments 12 to 32, wherein the composite contains an elastic non-woven or blanket, elastic particles, elastic shapes or an elastic frame surrounding aerogel layer (LA) providing elasticity to the composite when compressed mechanically.

[0195] 34. A composite obtained according to the process according to any one of embodiments 12 to 33.

[0196] 35. Use of a composite according to any one of embodiments 1 to 11 or embodiment 34 or a composite obtained or obtainable according to the process according to any one of embodiments 12 to 33 as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, automotive applications, infrastructure applications, marine applications, oil and gas applications or apparel, or as heat-shield material or material against thermal propagation in batteries.

[0197] Brief description of the figures:

[0198] Fig. 1 shows possible schematic structure of the cross-section of composites with different structure of layers.

[0199] Figure 1 (a) shows a schematic view of a cross-section of a composite with layers (LA), (LB) and (LC). The composite has a total thickness (LT) which follows the formulae:

[0200] (LT) - (LC) - (LB) = (LA) = (LA-1 ) + (LA-2)

[0201] Figure 1 (b) shows a schematic view of a cross-section of a composite with layers (LA), (LB), (LC), (LB’) and (LC’). The composite has a total thickness (LT) which follows the formulae:

[0202] (LT) - (LC) - (LC’) - (LB) - (LB’) = (LA) = (LA-1 ) + (LA-2) Figure 1(c) shows a schematic view of a cross-section of a composite with layers (LA), (LB) and (LC) with sections 1 , 2, 3 and with different thickness and an average thickness is obtained for layers (LA) and (LA-2):

[0203] Fig. 2 shows a schematic view of a cross-section of a composite with layers (LA), (LB) and (LC) with varying thickness of layers (LB) or (LB) and (LC).

[0204] Fig. 3 shows a schematic view of a cross-section of a composite with layers (LA), (LB), and (LC). Layer LC is a fibrous layer and binder covering the fibers resulting in an average thickness of layers (LA), (LB), (LC).

[0205] Examples will be used below to illustrate the invention.

[0206] EXAMPLES

[0207] 1 . Aerogel preparation

[0208] Aerogel particles were produced as follows: Colloidal silica (CS, Levasil CS15-340P from Nouryon) and sodium alginate (SA, Protanal LF120 from IFF) were blended with water to obtain a precursor solution at a given target concentration. 1 I of the precursor solution was dripped into a calcium chloride bath (20 g / l) of 5 I at room temperature to form hydrogel particles. Hydrogel particle size was controlled by the dripping method between 0.1 mm and 4 mm diameter. The water in the hydrogel particles was exchanged to -98% ethanol over ten steps against 98% ethanol by immersion in ten times of the particle volume of 98% ethanol for -3 hours at room temperature. The obtained alcogel particles were dried with supercritical CO2 to obtain aerogel particles. If required, the aerogel particles were ground to powder (particle size 10-100 pm) by blending in a kitchen blender for -60 s.

[0209] 2. Composite preparation

[0210] 2.1 Materials

[0211] Aerogel particles as described above. Glass fiber facing (thickness -0.2 mm). Hotmelt web (copolyester, 100 g / m2).

[0212] 2.2 Monolayer composite

[0213] Aerogel particles were layered on a first glass fiber facing (20x20 cm) and a first layer of hotmelt web (20x20 cm) and covered with a second layer of hotmelt web and glass fiber facing. The assembly was compressed to the target thickness under heating above the melting temperature of the hotmelt web for -30 s to obtain a layered composite sheet of aerogel particles bonded on two sides by the hotmelt web between two glass fiber facings. The hotmelt did not penetrate into the central part of the composite to create a binder-free layer of aerogel particles. 2.3 Multilayer composite

[0214] Aerogel particles were layered on a glass fiber facing with a layer of hotmelt web and covered with a layer of hotmelt web and then further alternating layers of ductile aerogel particles and hotmelt web. The assembly was covered with a final glass fiber facing and compressed to the target thickness under heating above the melting temperature of the hotmelt web for ~30 s to obtain a thick layered composite of aerogel particles. The overall thickness of the thick layered aerogel composite was controlled by number of layers.

[0215] 3. Composite test

[0216] CS: colloidal silica, SA: sodium alginate, T.C.: thermal conductivity (measured in Fox 200) composite pulled apart easily; +: composite not pulled apart easily. burning; +: not burning, may char.

[0217] Literature cited:

[0218] EP 0850206 B1 EP 0854892 B1

[0219] EP 0963358 B1

[0220] WO 2016 / 053399 A2

[0221] US 9097377 B2

[0222] PCT / EP2023 / 955870 Robitzer et aL, 2008, Langmuir, 24(21), 12547-12552

[0223] WO 2009 / 027310

Claims

Ciaims1 . A composite comprising two or more layers comprising:(a) a layer (LA) with a thickness in the range of from 0.1 to 4 mm comprising aerogel particles with a diameter in the range of from 0.1 to 4 mm before any compression, and(b) one adjacent binder layer (LB) with a thickness in the range of from 0.01 to 1 mm(c) optionally a support layer (LC) adjacent to the binder layer with a thickness in the range of from 0.01 to 3 mm,(d) optionally a second adjacent binder layer (LB’) and support or cover layer (LC’) on the second side of particle layer (LA), where aerogel particle layer (LA) comprises a layer section (LA-1) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and is located adjacent to binder layer (LB), and where the aerogel particle layer (LA) further contains a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm.

2. The composite according to claim 1 , where binder layer (LB) adheres to more than 60% of aerogel particles of layer (LA) and preferably adheres to support layer (LC).

3. The composite according to claim 1 or 2, where binder layer (LB) and support layer (LC) or binder layer (LB’) and (LC’) are combined.

4. The composite according to any one of claims 1 to 3, wherein the uncompressed aerogel particles of layer (LA) have one or more of features (a) to (y)(a) 80 - 99.6% porosity,(P) 15 - 200 kg / m3particle bulk density,(y) 16 - 30 mW / mK thermal conductivity measured at 10 °C of a loose filled particle bed.

5. The composite according to any one of claims 1 to 4, where the individual aerogel particles can be compressed to 5 - 98% of original thickness without visible breakage of the aerogel particle during compression with a compression rate from 0.01 to 5 mm / sec, or present less than 1 N drop in force due to primary breakage during compression.

6. The composite according to any one of claims 1 to 5, wherein,(I) the aerogel particle size distribution is monodisperse or polydisperse or partially monodisperse, and / or(II) sphericity of the individual aerogel particle ranges from 25% to 100%.

7. The composite according to any one of claims 1 to 6, wherein the aerogel is a silica- based aerogel comprising(A) 20-80% silica by mass and 20% of ionically crosslinkable polycarboxylate polymer but at least 25 kg / m3ionically crosslinkable polycarboxylate polymer, or(B) 20-90% silica by mass and 10% alginate by mass but at least 15 kg / m3alginate, or(C) 20-85% silica by mass and 15% pectin by mass but at least 20 kg / m3pectin, or(D) 20-80% silica by mass and 20% CMC by mass but at least 25 kg / m3CMC, or(E) 20-85% silica by mass and 7.5% alginate by mass and at least 15 kg / m3alginate and at least 10 kg / m3of non-alginate ionically crosslinkable polycarboxylate polymer.

8. The composite according to any one of claims 1 to 7 wherein herein the binder is selected from the group consisting of reactive binders based on acrylates, polyurethanes, epoxy resins, silicone or water glass or other inorganic binder systems, or from thermoplastic binders based on PE, PP, PA, TPU, PLA or other bio-based polymers, silicone, or on mixtures of any of those binders.

9. Process for preparing a composite comprising two or more layers comprising the steps of(i) forming a binder layer (LB),(ii) forming a layer comprising aerogel particles (LA) with a diameter in the range of from 0.1 to 4 mm before any compression,(iii) forming a composite comprising layers (LA) and (LB) by applying condition suitable to achieve stable bonding between layers (LA) and (LB) and formation of a layer section (LA-1 ) with a thickness of 0.01 to 1 mm which contains both binder and aerogel particles and a layer section (LA-2) free of binder with a thickness of equal to or more than 0.05 mm, wherein the uncompressed aerogel particles of layer (LA) preferably have one or more of features (a) to (y)(a) 80 - 99.6% porosity;(P) 15 - 200 kg / m3particle bulk density;(y) 16 - 30 mW / mK thermal conductivity measured at 10°C of a loose filled particle bed.

10. The process according to claim 9, wherein the aerogel is a silica-based aerogel.11 . The process according to any one of claims 9 to 10, wherein the process comprises the steps of(iv) compressing the composite such that the aerogel is compressed to 5 - 98% of original thickness,(v) applying a compression rate in the range between 0.01 - 1 mm / sec.

12. The process according to any one of claims 9 to 11 , wherein the thickness of the composite is in the range of 0.1 to 20 mm.

13. The process according to any one of claims 9 to 12, wherein the thickness of the layer (LA) comprising aerogel particles is in the range of from 0.1 to 4 mm.

14. The process according to any one of claims 9 to 13, wherein the binder is selected from the group consisting of acrylates, polyurethanes, epoxy resins, silicone or thermoplastic binders such as PE, PP, PA, TPU PLA.

15. Use of a composite according to any one of claims 1 to 8 or a composite obtained or obtainable according to the process according to any one of claims 9 to 14 as thermal insulation material for building and construction, appliances, thermologistics, cryogenic applications, automotive applications, infrastructure applications, marine applications, oil and gas applications or apparel, or as heat-shield material or material against thermal propagation in batteries.

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