MXPA98001908A - Aerogel mixed material that contains fib - Google Patents

Abstract

The present invention relates to a mixed material containing from 5 to 97% by volume of airgel particles, at least one binder and at least one fiber material, the diameter of the airgel particles being > - 0.5 mm, a procedure to manufacture it, and the use of

Description

AEROGEL MIXED MATERIAL THAT CONTAINS FIBERS DESCRIPTIVE MEMORY The present invention relates to a mixed material containing from 5 to 97% by volume of airgel particles, at least one binder, and at least one fiber material, the diameter of the airgel particles being > 0.5 mm, a procedure to make it, and the use of it. Due to their very low density, high porosity and small pore diameters, aerogels, particularly those with a porosity of more than 60% and densities of less than 0.4 g / cm3, exhibit extremely low thermal conductivity and, for this reason , they are used as materials for thermal insulation, as described in EP-A-0 171 722, for example. However, its high level of porosity leads to a low mechanical stability, both of the gel from which the airgel dries, and of the dried airgel itself. In the broadest sense, that is, when they are considered "gels that have air as a dispersant", aerogels are manufactured by drying a suitable gel. When used in this sense, the term "airgel" includes aerogels in the narrowest sense, such as xerogels and cryogels. A gel is designated as an airgel in the narrowest sense if the liquid is removed from the gel at temperatures above the critical temperature and starting from pressures that are above the critical pressure. In contrast to this, if the liquid is removed from the gel subcritically, for example, with the formation of a vapor-liquid boundary phase, then the resulting gel is known, in many cases, as xerogel. It should be noted that the gels according to the present invention are aerogels in the sense that they are gels having air as a dispersant. The procedure that configures the airgel is concluded during the sol-gel transition. After the solid structure of the gel has been formed, the external configuration can only be changed by size reduction, for example, by spraying. The material is too fragile for any other form of tension. However, for many applications, it is necessary to use airgel in certain configurations. In principle, the production of molded parts is possible even when the gel is being formed. However, the replacement of solvents that is determined by diffusion (with respect to aerogels, see, for example, US-A-4 610,863 and EP-A-0 396 0761), with respect to mixed airgel materials, see, for example, WO 93/06044), and drying - which is likewise determined by diffusion - leads to production times that are economically unacceptable. For this reason, it is appropriate to carry out a configuration step after producing the airgel, that is, after it has been dried, and to do this without any essential change of the internal structure of the airgel occurring with respect to the particular application. . However, for many applications, in addition to good thermal insulation, an insulating material is also required to provide good insulation against airborne sound. Typically, good sound insulation is found in porous materials, the porosity of which lies on a macroscopic scale (greater than 0.1 μm) when the speed of the sound waves is attenuated by air friction on the walls of the pores. For this reason, monolithic materials without any macroscopic porosity display only a very low level of acoustic damping. If a material is barely porous on a microscopic scale, as is the case with monolithic aerogels, air can not flow through the pores; rather, the sound waves are transmitted to the structure of the material, and the latter then conducts them without any marked attenuation. DE-A 33 46 180 describes rigid panels made from molded bodies based on silicic acid airgel obtained by flame pyrolysis combined with reinforcement by long mineral fibers. Nevertheless, this silicic acid airgel that is extracted from the flame pyrolysis is not an airgel in the above sense, since it is not manufactured by drying a gel and, for this reason, it has a completely different pore structure. Mechanically, it is much more stable and for this reason it can be pressed without destroying its microstructure, although it has a higher thermal conductivity than typical aerogels in the previous sense. The surface of a molded body such as this is extremely delicate and, for this reason, must be hardened, either by the use of a binder or by being covered with a film. EP-A-0 340 707 describes an insulating material with a density of 0.1 to 0.4 g / cm3 consisting of at least 50% by volume of silica airgel particles with a diameter between 0.5 and 5 mm, which are connected by medium of at least one organic and / or inorganic binder. If the airgel particles are connected by the binder only on the contact surfaces, the resulting insulating material is not very stable in the mechanical sense since, under mechanical stress, the part of the airgel particle that is covered with the binder is separates, so that the particle is no longer connected and the insulating material cracks. For this reason, as soon as possible, all spaces between the airgel particles should be filled with the binder. In the case of very small proportions of binder, the resulting material is as stable as pure aerogels, although cracking can very easily occur if all grains of the granulated material are not sufficiently enclosed by the binder. In the case of a high volumetric percentage of binder which is favorable for achieving a low level of thermal conductivity, only very small proportions of the binder will remain in the spaces between the particles and, especially in the case of porous binders such as foams with thermal conductivity. lower, this will result in low mechanical stability. In addition, due to the reduced macroscopic porosity (between the particles), filling all intermediate spaces with binder causes markedly reduced acoustic damping within the material. EP-A-489 319 describes a mixed foam with a low level of thermal conductivity, containing from 20 to 80% by volume of silica airgel particles, 20 to 80% by volume of a styrene polymer foam with a density from 0.01 to 0.15 g / cm3 that encloses the airgel particles and connects them together and, if necessary, effective amounts of the usual additives. The mixed foam produced in this way is resistant to compression, but is not very rigid at high concentrations of airgel particles. German Patent Applications DE-A 44 30 669 and DE-A-44 30 642 describe fiber reinforced airgel panels or mats. It is true that, due to the very high proportion of airgel, these panels or mats display a very low level of thermal conductivity, but require relatively long production times due to the diffusion problems described above. German Patent Application P 44 45 771.5 not yet published, discloses a mixed non-woven fiber airgel-textile material having at least one layer of non-woven fiber fabric and airgel particles, and which is characterized in that the textile of nonwoven fiber contains at least one fiber binary material, whose fibers are connected to each other and to the airgel particles by the low melting point coating material. This mixed material has a relatively low level of thermal conductivity and a high level of macroscopic porosity and, due to this, good acoustic damping, although the scale of temperature at which the material can be used, and its characteristic of protection against fire, they are restricted by the use of binary fibers. In addition, the corresponding mixed materials, in particular complex molded bodies, are not easy to manufacture. For this reason, one of the objectives of the present invention was to produce a mixed material which was based on granulated airgel material, which had a lower level of thermal conductivity, and which was both mechanically stable and easy to manufacture. A further objective of the present invention was to produce a mixed material that was based on granular airgel material, and which would further display good acoustic damping characteristics. This objective is achieved by a mixed material containing from 5 to 97% by volume of airgel particles, at least one binder and at least one fiber material, the diameter of the airgel particles being >; 0.5 mm. The fibers or aerogels are connected to each other and to each other by the binder, or the binder serves as a matrix material in which the fibers and airgel particles are embedded. The connection of the fibers and the airgel particles to one another and to one another by the binder and, optionally, including them in a binder matrix, results in a mechanically stable material of very low thermal conductivity. In contrast to a material consisting solely of airgel particles that are connected by their surfaces or embedded in an adhesive matrix, more surprisingly, even small proportions of fibers in volume can result in significant mechanical strength, given an equal proportion of binder in volume, since they assume a large part of the load. If a larger volume of fibers is used, with only a small amount of binder, it is possible to obtain a porous material in which the fibers that are connected by the binder form a mechanically stable structure within which the airgel particles are embedded. The resulting pores of air then lead to a higher porosity level, and thus to improved acoustic damping. Natural fibers such as cellulose, cotton or flax fibers, as well as synthetic fibers, can be used as the fiber material; With respect to synthetic fibers, it is possible to use inorganic fibers such as glass fibers, mineral fibers, silicon carbide fibers or carbon fibers; and using polyester fibers, polyamide fibers or polyaramide fibers as organic fibers. The fibers may be new, or a waste material such as shredded fiberglass waste or waste debris. The fibers can be straight or wavy, and be in the form of individual fibers, wadding, or a woven or non-woven fiber material. The fiber material and / or the non-woven fabrics can be contained in the binder in the form of a cohesive whole and / or in the form of several small pieces. The fibers can be round, trilobal, pentalobular, octalobular, in the form of strips, or be shaped into spruce, weights or other shapes. Hollow fibers can also be used. The diameter of the fibers that are used in the mixed material should preferably be less than the average diameter of the airgel particles, so that a large proportion of the airgel is bound in the mixed material. The selection of very fine fibers makes the mixed material slightly flexible. It is preferred to use fibers with diameters that are between 0.1 μm and 1 mm. Typically, in the case of fixed fiber proportions by volume, the use of smaller diameters results in mixed materials that are more resistant to breakage. There are no restrictions on fiber lengths. Preferably, however, the lengths of the fibers must be greater than the average diameter of the airgel particles, ie, at least 0.5 mm. In addition, mixtures of the above types can be used. The stability and thermal conductivity of the mixed material increase as the proportion of fibers increases. The volume percentage of the fibers should preferably be between 0.1 and 40% by volume, and in particular on the scale between 0.1 and 15% by volume, depending on the application. To improve the way in which they are joined in the matrix, the fibers can be coated with sizing or coupling agents, as is typically done in the case of glass fibers. Aerogels suitable for the composition according to the present invention are those based on metal oxides, which are suitable for the sol-gel technique (CJ Brin er, GW Scherer, Sol-Gel Science, 1990. Chapters 2 and 3), for example, Si or Al compounds such as those based on organic substances that are suitable for the sol-gel technique, such as melamine-formaldehyde condensates (US-A-5 086 085) or resorcinformaldehyde condensates (US-A-4 873 218). They can also be based on mixtures of the materials mentioned above. It is preferred to use aerogels containing Si compounds, especially SÍO 2 aerogels, and in particular SióO2 aerogels. The airgel may contain IR light opacifiers, such as soot, titanium dioxide, iron oxide or zirconium dioxide, as well as mixtures thereof, to reduce the contribution of radiation to thermal conductivity. In addition, the thermal conductivity of aerogels decreases as porosity increases and density decreases; this is applied under densities in the neighborhood of 0.1 g / cm3. For this reason, aerogels with porosities of more than 60% and densities between 0.1 and 0.4 g / cm3 are especially preferred. It is preferred that the thermal conductivity of the granulated airgel material is less than 40 mW / mK, and in particular less than 25 mW / mK. In a preferred embodiment, hydrophobic airgel particles are used; these can be obtained by incorporating hydrophobic surface groups on the surface of the pores of the aerogels during or after the production thereof. In the present application, the term "airgel particles" is used to designate particles that are monolithic, that is, they are composed of one piece or, essentially, airgel particles with a diameter that is smaller than the diameter of the particles that they are joined by a suitable binder and / or they are compressed to form a larger particle. The size of the grains will depend on the use that is going to be given to the material. To achieve a higher level of stability, the granulated material should not be too thick, and it is preferred that the diameter of the grains be less than 1 cm and, in particular, less than 5 mm. On the other hand, the diameter of the airgel particles should be greater than 0.5 mm to avoid the difficulties associated with the handling of a very fine, low density powder. In addition, as a rule, during processing, the liquid binder penetrates into the upper layers of the airgel which, in this area, loses its great efficiency as insulation. For this reason, the ratio of the surface of macroscopic particles to the volume of particles should be as small as possible, which would not be the case where the particles are too small. To achieve a low thermal conductivity on the one hand, and on the other hand, to achieve adequate mechanical stability of the mixed material, the volume percentage of the airgel should preferably be between 20 and 97% by volume, and especially between 40 and 95% by volume. volume, in which case the higher volume percentages result in lower thermal resistance and conductivity. To achieve a high level of porosity of the material in general, and increased acoustic absorption, air pores must be incorporated in the material, for which purpose the volume percentage of the airgel should preferably be less than 85% by volume.

Granular material with a bimodal distribution of favorable grain size can be used to achieve a high volume percentage of airgel. Other distributions may also be used, depending on the application, for example, in the acoustic damping area. The fibers or airgel particles are connected to each other, and the fibers and airgel particles are connected to each other by at least one binder. The binder can only serve to join the fibers and the airgel particles together and with each other, or it can serve as a matrix material. In principle, all known binders are suitable for manufacturing the mixed materials according to the present invention. Inorganic binders such as water glass adhesive or organic binders, or mixtures thereof, can be used. The binders may also contain additional organic and / or inorganic components. Suitable organic binders are, for example, thermoplastics such as polyolefins or polyolefin waxes, styrene polymers, polyamides, ethylene-vinyl acetate copolymers, or mixtures thereof, or duroplasts such as phenol, resorcin, urea or melamine resins. . Adhesives such as melt adhesives, dispersion adhesives (in aqueous form, for example, styrene butadiene, and styrene-acrylic ester copolymers), solvent adhesives or plastisols; Also suitable are reaction adhesives, for example, in the form of unitary systems such as heat-cured epoxy resins, formaldehyde condensates, polyimides, polybenzimidazoles, cyanoacrylates, polyvinylbutyrals, polyvinyl alcohols, anaerobic adhesives, polyurethane adhesives and hardened silicones with moisture, or in the form of binary systems such as methacrylates, cold-hardened epoxy resins, binary silicones and cold-hardened polyurethanes. It is preferred to use polyvinyl butyrals and / or polyvinyl alcohols. It is preferred that the binder be selected so that if it is in liquid form during the specific phases of the processing, during this time interval it can not penetrate into the very porous airgel, or can only penetrate to an insignificant degree. Penetration of the binder into the airgel particles can be controlled by selecting the binder and regulating processing conditions such as pressure, temperature and mixing time. If the binder forms a matrix in which the aerogels and fibers are embedded, then, due to their low thermal conductivity, porous materials with densities of less than 0.75 g / cm 3 are used, such as foams, preferably polymer foams ( example, polystyrene or polyurethane foams). To achieve good distribution of the binder in the interstices when using large proportions of airgel, and to achieve good adhesion, in case a solid binder form is used, the grains of the binder should preferably be smaller than those of the material granulated airgel. Higher pressure processing may also be required. If the binder has to be processed at elevated temperatures, such as in the case of melt adhesives or reaction adhesives such as, for example, melamine-formaldehyde resins, then the binder must be selected so that its melting temperature does not exceed the melting temperature of the fibers. In general, the binder is used at a rate of 1 to 50% by volume of the mixed material, preferably at a rate of 1 to 30% by volume. The selection of the binder will be determined by the thermal and mechanical demands imposed on the mixed material, as well as by the requirements with respect to fire protection. The binder may also contain effective amounts of other additives such as, for example, coloring agents, pigments, diluents, fire retardant agents, synergists for fire protective agents, antistatic agents, stabilizers, softeners and infrared light opacifiers.

In addition, the mixed material may also contain additives that are used to make it or that are formed when it is manufactured; said substances may include compression slip agents, such as zinc stearate, or the reaction products formed from acid or hardening accelerators by acid separation, when resins are used. The fire protection characteristic of the mixed material is determined by the fire protection characteristics of the airgel, the fibers and the binder and - optionally - by those of the other substances contained therein. To achieve the most favorable fire protection characteristic for the mixed material, non-flammable fibers such as glass or mineral fibers, or fibers that are difficult to ignite, such as TREVIRA CSR, or melamine resin fibers, aerogels are used based on inorganic substances, preferably based on SIO2; binders that are difficult to ignite are also used, such as inorganic urea binders and melamine-formaldehyde resins, silicon resin adhesives, and polyimide and polybenzimidazole resins. If the material is used in the form of flat structures such as panels or mats, these can be coated on at least one side with at least one coating layer to improve their surface properties, and to make them stronger, form them as a barrier against steam, or protect them against dirt. These coating layers can also improve the mechanical stability of the molded parts made of the mixed material. If coating layers are used on both sides, these can be identical or different. All materials known to those skilled in the art are suitable for use as coating layers. They can be non-porous and thus act as a vapor barrier, for example, plastic films, preferably metal films, or metallized plastic films that reflect thermal radiation. It is also possible to use porous coating layers such as porous films, papers, textiles or non-woven fabrics that allow air to penetrate the material and thus increase its acoustic damping properties. The coating layers may themselves consist of a plurality of layers. The coating layers can be secured with the binder that binds the fibers and airgel particles together and with each other, although a different adhesive can also be used. The surface of the mixed material can be sealed and consolidated also incorporating at least one suitable material in a surface layer. Suitable materials are thermoplastic polymers such as polyethylene and polypropylene, or resins such as melamine-formaldehyde resins. It is preferred that the mixed materials according to the present invention have a thermal conductivity that is between 10 and 100 mW / mK, especially in the range of 10 to 50 mW / mK, and in particular in the range of 15 to 40 mW / mK. A further objective of the present invention was to provide a method for manufacturing the mixed materials according to the present invention. If the binder is initially in the form of a powder that melts at an elevated temperature and, if necessary, at a high pressure and then reacts, as in the case of the reaction adhesives, then the mixed material can be obtained as follows : the aerolgel particles, the fiber material and the binder are mixed using conventional mixers. The mixture is then subjected to a configuration procedure. The mixture will be hardened in the mold by heating, if necessary under pressure, depending on the type of binder, for example, in the case of reaction adhesives, or in the case of melt adhesives being heated to a point above the point of fusion of the binder. A material that is porous on a macroscopic scale can be obtained, in particular, in accordance with the following procedure: in case the fibers are no longer in the form of batting (for example, small tassels of short fibers, or small pieces of a film), they will be processed to form small tassels by methods well known to those skilled in the art. Even in this step it is possible, if necessary, to incorporate the granulated airgel material between the fibers. Subsequently, these tassels are mixed together with the binder and, optionally, the airgel particles, for example in a mixer, until the binder and, optionally, the airgel particles are distributed as evenly as possible between the fibers. The compound is then placed in a mold and, if necessary, under pressure, and heated to a temperature which, in the case of melt adhesives, is above the melting temperature of the adhesive and, in the case of Reaction adhesives, be above the temperature that is required for the reaction. After the binder has melted or reacted, the material cools. It is preferred to use polyvinylbutyrals here. The density of the mixed material can be increased using a higher pressure. In a preferred embodiment, the mixture is compressed. When this is done, the person skilled in the art can select the press and pressure die that are most suitable for the particular application. If necessary, skilled artisans can add known glidants, such as zinc stearate, to the pressing process when melamine-formaldehyde resins are used. The use of vacuum presses is particularly advantageous due to the large amount of air in the molding compound contained in the aerogels. In a preferred embodiment, the molding compound containing the airgel is compressed to form panels. To avoid cooking the compound on the pressure hub, the mixture containing the airgel and to be compressed can be separated from the pressure hub by releasable paper. The mechanical strength of the panels containing the airgel can be increased by laminating the mesh fabrics, non-woven fabrics or papers on the surface of the panel. These mesh textiles, non-woven fabrics or papers can subsequently be applied to the panels containing the airgel, in which case the mesh fabrics, the nonwovens or the papers are previously impregnated with suitable binder or adhesive, and then they are bonded to the surface of the panel in a heated press when they are under pressure. Furthermore, in a preferred embodiment, this can be done in one step by accumulating mesh textiles, nonwovens and paper, optionally pre-impregnated with a suitable binder or adhesive, in the pressure mold, and applying them to the molding compound that it contains the airgel and which is to be pressed, and then subjected to pressure and elevated temperatures to form a mixed panel containing aerogels. Depending on the binder used, in any mold, the pressing usually occurs at pressures of 1 to 1000 bar and at temperatures of 0 to 300 ° C. In the case of phenol, resorcin, urea and melamine-formaldehyde resins, the pressing preferably occurs at pressures of 5 to 50 bar, especially at 10 to 20 bar, and at temperatures preferably 100 to 200 ° C, especially 130 to 190 ° C. , and in particular between 150 and 175 ° C. If the binders are initially in liquid form, the mixed material can be obtained in the following manner: the airgel particles and the fiber material are mixed using conventional mixers. The mixture thus obtained is then coated with the binder, for example, by spraying, placed in a mold and then hardened in this mold. Depending on the type of binder used, the mixture hardens under pressure by heating and / or evaporating the solvent or dispersant used. It is preferred that the airgel particles are subjected to swirling action with the fibers in a gas flow. A mold is then filled with the mixture, and the binder is sprinkled during the filling process. A material that is porous on a macroscopic scale can be obtained in the following way: in case the fibers are no longer in piled form (for example, small tassels of short fibers, or small pieces of non-woven fabric), they are processed in small tassels using methods that are known to those skilled in the art. Even in this step, the granulated airgel material can be incorporated, if necessary, between the fibers. Otherwise, these tassels are mixed with the granulated airgel material in a mixer until the airgel particles have been distributed as uniformly as possible between the fibers. In this step, or subsequently, the binder is sprinkled, divided as finely as possible over the mixture, and the mixture is then placed in a mold and heated - if necessary under pressure - to the temperature that is required so that the agglutination occurs. Subsequently, the mixed material is dried using a conventional method. If a foam is used as a binder, the mixed material can be produced as follows, depending on the type of foam used. If the foam is made in a mold by expanding expandable grains of granular matter, as in the case of expanded polystyrene, all of the components can be completely mixed and typically then heated, advantageously by hot air or steam. Due to the expansion of the particles, the pressure in the mold increases, which means that the interstices are filled with foam and the airgel particles are fixed in the mixed material. After cooling, the molded part of the mixed material is removed from the mold and dried, if necessary. If the foam is manufactured by extrusion or expansion of a non-viscous mixture, with subsequent solidification, the fibers can be mixed in the liquid. The airgel particles are mixed in the resulting liquid, which then foams. If the material is to be provided with a coating layer, it can be deposited in a mold, before or after the filling process, so that the coating and the configuration can occur in one step, in which the binder used for the material mixed is also used as a binder for the coating. However, it is also possible to provide the mixed material with a coating layer in a subsequent step. The configuration of the molded part consisting of the mixed material in accordance with the present invention is in no way restricted; in particular, the mixed material can be configured in panels. Due to the high percentage of airgel and its low thermal conductivity, mixed materials are particularly well suited as thermal insulation. Formed into panels, the mixed material can be used as sound absorbing material, either directly or in the form of resonance absorbers for sound insulation. In addition to the cushioning of the airgel material, depending on the porosity resulting from macroscopic pores, additional cushioning is provided as a result of the air friction on these macroscopic pores in the mixed material. The macroscopic porosity can be regulated by changing the proportion of fibers and their diameter, the grain size, the proportion of airgel particles and the type of binder. The frequency function of the acoustic damping and its degree can be changed by selecting the coating layer, the thickness of the panel and its macroscopic porosity, which is done in a manner known to those skilled in the art. Due to their macroscopic porosity and, in particular, to their high porosity, and to the specific surface of the airgel, the mixed materials according to the present invention are also suitable as adsorption materials for liquids, vapors and gases. The present invention will be described in greater detail below on the basis of examples of modalities without, however, being restricted by them: EXAMPLE 1 Molded part of airgel. polyvinyl butyral and fibers 90% by volume of hydrophobic granulated airgel material, 8% by volume of polyvinylbutyral powder Mowital® (Polymer F) and 2% by volume of high-strength Trevira® fibers are thoroughly mixed. The hydrophobic granulated airgel material has an average grain size in the range of 1 to 2 mm, a density of 120 kg / m3, a BET surface area of 620 p / g and a thermal conductivity of 11 mW / mK. The bottom of the pressure mold, with a base area of 30 cm x 30 cm, is covered with release paper. The molding material containing the airgel is uniformly applied thereto, and everything is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220 ° C for a period of 30 minutes. The molded part obtained in this way has a density of 269 kg / m3 and a thermal conductivity of 20 mW / mK.

EXAMPLE 2 Molded part of airgel. polyvinyl butyral and recirculation fibers 80% by volume of hydrophobic granulated airgel material as described in Example 1, 10% by volume of polyvinylbutyral powder Mowital® (Polymer F) and 10% by volume of coarse crumbled polyester fiber residues are thoroughly mixed as the recirculation fibers. The bottom of the pressure mold, with a base area of 30 cm x 30 cm, is covered with release paper. The molding material containing the airgel is uniformly applied thereto, and everything is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220 ° C for a period of 30 minutes. The molded part obtained in this way has a density of 282 kg / m3 and a thermal conductivity of 25 mW / mK.

EXAMPLE 3 Molded part of airgel. polyvinyl butyral and recirculation fibers 50% by volume of hydrophobic granulated airgel material as described in Example 1, 10% by volume Mowital polyvinylbutyral * powder (Polymer F) and 40% by volume of coarse crumbled polyester fiber residues are thoroughly mixed. as the fibers of recirculation. The bottom of the pressure mold, with a base area of 30 cm x 30 cm, is covered with release paper. The molding material containing the airgel is uniformly applied thereto, and everything is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220 ° C for a period of 30 minutes. The molded part obtained in this way has a density of 420 kg / m3 and a thermal conductivity of 55 mW / mK.

EXAMPLE Molded part of airgel. polyethylene wax and fibers 60% by weight of hydrophobic granulated airgel material as described in Example 1 and 38% by weight of Ceridust polyethylene wax powder "130, and 2% by volume of high strength" T "fibers are thoroughly mixed. The bottom of the pressure mold, with a base area of 12 cm x 12 cm, is covered with release paper. The molding material containing the airgel is applied evenly to this, and everything is then covered with release paper. A pressure of 70 bars is applied at 170 ° C for 30 minutes. The molded part obtained in this way has a thermal conductivity of 25 mW / mK.

EXAMPLE 5 Molded part of airgel. polyethylene wax and fibers 50% by weight of hydrophobic granulated airgel material as described in Example 1 and 48% by weight of Hoechst-Wachs PE 520 polyethylene wax powder, and 2% by volume of high strength Trevira® fibers are thoroughly mixed. The bottom of the pressure mold, with a base area of 12 cm x 12 cm, covered with release paper. The molding material containing the airgel is applied evenly to this, and everything is then covered with release paper. A pressure of 70 bars is applied at 180 ° C for 30 minutes. The molded part obtained in this way has a thermal conductivity of 28 mW / mK.

EXAMPLE 6 Molded part of airgel. polyvinyl alcohol and fibers 90% by weight of hydrophobic granulated airgel material is thoroughly mixed as described in Example 1, 8% by weight of a polyvinyl alcohol solution and 2% by volume of high strength Trevira® fibers. The polyvinyl alcohol solution consists of 10% by weight of Mo iol R type 41-88, 45% by weight of water and 45% by weight of ethanol. The bottom of the pressure mold, with a base area of 12 cm x 12 cm, is covered with release paper. The molding material containing the airgel is uniformly applied thereto, and everything is then covered with release paper, after which it is pressed at a pressure of 70 bar for a period of 2 minutes, and then dried. The molded part obtained in this way has a thermal conductivity of 24 mW / mK. The thermal conductivity of the granulated airgel material was measured by a hot wire method (see, for example, 0. Nielsson, G. R? Schenpohler, J. Groß, J. Fricke, High Tempe ratures-High Pressures, vol. 21, pp. 267-274 (1989)).

The thermal conductivity of the molded parts was established in accordance with DIN 52612.

Claims (20)

NOVELTY OF THE INVENTION CLAIMS

1. - A mixed material containing from 5 to 97% by volume of airgel particles, at least one binder and at least one fiber material, the diameter of the airgel particles being > 0.5 mm.

2. The mixed material according to claim 1, characterized in that the volume percentage of the fiber material is 0.1 to 40% by volume.

3. The mixed material according to claim 1 or claim 2, characterized in that the fiber material contains glass fibers as the main component.

4. The mixed material according to claim 1 or claim 2, characterized in that the fiber material contains organic fibers as the main component.

5. The mixed material according to at least one of claims 1 to 4, characterized in that the proportion of airgel particles is in the range of 20 to 97% by volume.

6. The mixed material according to at least one of claims 1 to 5, characterized in that the porosity of the airgel particles is greater than 60%, its density is less than 0.4 g / cm3, and its thermal conductivity is less than 40 mW / mK.

7. The mixed material according to at least one of claims 1 to 6, characterized in that the airgel is a SIOO2 airgel which, if necessary, has been modified organically.

8. The mixed material according to at least one of claims 1 to 7, characterized in that at least some of the airgel particles have hydrophobic surface groups.

9. The mixed material according to at least one of claims 1 to 8, characterized in that the binder is of a density that is less than 0.75 g / cm3.

10. The mixed material according to at least one of claims 1 to 9, characterized in that the binder contains an inorganic binder as the main component.

11. The mixed material according to claim 10, characterized in that the inorganic binder is water glass.

12. The mixed material according to at least one of claims 1 to 9, characterized in that the binder contains an organic binder as a main component.

13. The mixed material according to claim 12, characterized in that the organic binder is polyvinyl butyral and / or polyvinyl alcohol.

14. The mixed material according to at least one of claims 1 to 13, characterized in that at least some of the airgel particles and / or the binder contain at least one infrared light opaver.

15. The mixed material according to at least one of claims 1 to 14, characterized in that it is flat and is covered on at least one side with at least one recovery layer.

16. A process for manufacturing a mixed material according to at least one of claims 1 to 15, characterized in that the airgel particles and the fiber materials are mixed with the binder, and the mixture is subjected to configuration and hardening.

17. The use of a mixed material according to at least one of claims 1 to 15 for thermal and / or acoustic insulation.

18. The molded part containing a mixed material according to at least one of claims 1 to 15.

19. The molded part consisting essentially of a mixed material according to at least one of claims 1 to 15. The molded part according to claim 18 or claim 19, characterized in that it is in the form of a panel.