Aerogel-containing composite materials, process for producing the same and their use

Description: TECHNICAL FIELD [Detailed description of the invention]

Airgel composites, their manufacturing methods and their use The present invention relates to airgel composites, methods of their manufacture and their use. Porousness greater than 60% and 0.6 g / cm³Airgel with less than density Also have extremely low thermal conductivity due to their extremely low density and high porosity Tsu. However, due to its high porosity, it is then dried to give an airgel. Not only the mechanical stability of the dried airgel itself, but also the mechanical stability of the dried airgel itself is reduced. .. Airgel is not extremely flexible and is extremely brittle. Aeroge in a broad sense, that is, "gel containing air as a dispersion medium" Lus are prepared by drying a suitable gel. Eroge in this sense The term "le" is a narrowly defined airgel, xerogel and cryogel. Including gels). Dry gel is the critical pressure of the gel liquid at a temperature higher than the critical temperature. It is an airgel in the narrow sense when it is substantially removed starting from a pressure higher than the force. To. In contrast, gel liquids are subcritical, for example for the formation of liquid-vapor boundary phases. When removed more, the resulting gel is called a xerogel. Smell of this specification The term "airgel" used in the broad sense, that is, "" unless otherwise specified. It means airgel in the sense of "gel containing air as a dispersion medium". Capillary force creates extremely high stress when drying general gels, which is remarkable. Combined with the low stability of the porous gel structure, it causes disintegration during the drying process. Inui Capillary pressure P generated during the drying process_cIs the surface tension Y of the surface between the pore liquid 2 and its vapor 4._LV, The contact angle between the liquid meniscus and the pore wall 3, and the radius r of the pore 1. Determined (Fig. 1):<img file="JPH10504792A_D0001.tif" /> This collapse is, for example, European Patent Application Publication EP-A-0382310, EP- Described in A-0018955 and US Pat. No. US-A-4,610,863 The gel is supercritically dried so that the surface tension Y_LVReduced to zero It can be avoided by letting it. However, the airgel produced in this way is mechanically Not very stable. International patent application publication WO 93/06044 states that airgel is fiber-reinforced. Fiber reinforced monolithi whose mechanical stability is considerably superior to that of non-reinforced airgel It discloses that a monolithic airgel can be obtained. But fiber strength The flexibility of fiber-reinforced monolithic materials is greater than that of pure airgel. The resulting sheet has a high elastic modulus. Furthermore, publication of international patent application The manufacturing method described in WO 93/06044 requires supercritical drying. Therefore, it is technically extremely difficult. It makes the gel alcohol, for example methanol To dry at a temperature of 250-260 ° C and a pressure of 9.7-15.9 MPa Accompanied by that. West German Patent Application Publication DE-A-43 42 548 and International Patent Application Publication For Kai WO 94/25149, 0.3g / cm³Less than density and greater than 60% A method for producing a xerogel having a key porosity is described, in which the gel is described. Does not require supercritical drying. This gel can be air-dried without collapsing, For example, SiO₂In the case of xerogel, the internal surface area is treated by silylation. It is reformed by. The xerogel produced in this way is also mechanically extremely cheap. It is not constant and breaks easily. There are many applications, such as use as insulation for curved surfaces, in which case Airgels in the form of flexible shapes, i.e. extremely flexible sheets or mats, can be used Would be desirable. However, the prior art airgel is highly brittle, so This is hindered. An object of the present invention is a porosity greater than 60% and 0.6 g / cm.³Less than density and To provide an extremely flexible airgel with. Therefore, the present invention has a porosity greater than 60% and 0.6 g / cm.³Less than density It is a mat-shaped composite material containing airgel having and and fibers dispersed therein. Tsu The above airgel has cracks, and the average capacity is 0.001 mm.³Ka 1 cm³The airgel fragment surrounded by the fissure is formed by the above fibers. Provided are the composite materials described above, which are retained in the fold. The composite material of the present invention is preferably 0.1 to 30 mm.³A with an average capacity of Contains Rogel fragments. The smaller the average volume of composite fragments, the more mechanical the composite Great flexibility. In addition, the flexibility of composites is the flexibility of fibers and airgels. Therefore, it is affected. Typically, the composites of the invention are fibrous according to the prior art. It is more flexible than monolithic aerogels made with or without conversion. The airgel suitable for the composite material of the present invention is a metal oxide suitable for the sol-gel method. CJ Brinker, GWScherer, Sol-Gel Scie nce, 1990, Chapters 2 and 3), for example of silicon or aluminum Compound-based or organic substances suitable for the sol-gel process, such as Based on lamin-formaldehyde condensate (US Pat. No. US-A-5,0) 86,085), or based on resorcinol-formaldehyde condensate (US Pat. No. US-A-4,873,218). They are the above substances It may be based on a mixture of. Airgels containing silicon compounds, especially SiO₂Prefer to use airgel I'm sorry. To reduce the involvement of radiation in thermal conductivity, airgel is IR opaque IR opacifiers such as carbon black, titanium dioxide, iron oxide Alternatively, it may contain zirconium dioxide or a mixture thereof. For coloring the gel may optionally contain dyes and / or colored pigments. It is particularly preferable to use xerogel, which is SiO₂Xerogel is especially good Good. The fiber material used is inorganic fiber, for example glass fiber or mineral fiber, organic fiber. , For example polyester fiber, aramid fiber, nylon fiber, or plant-derived It may be a fiber or a blend thereof. The fibers are coated For example, it may be a polyester fiber metallized with a metal such as aluminum. The coating is on the fibers and on the glass in fiberglass reinforced plastic It also helps improve the binding of airgel to the binder on the fiber. The fire class of composite materials is the fire resistance of airgel and textile materials, etc. It depends on the grade. Optimal fire resistance grade (low flammability or non-flammability) for the above composites ) Is obtained from non-flammable materials such as mineral or fiberglass Or should consist of low flammability fibers, such as melamine resin fibers. Sa In addition, for heat treatment that does not significantly change the structure of the airgel and therefore the thermal conductivity. Therefore, the organic component of the aerogel matrix can be eliminated. To avoid increasing thermal conductivity due to the contained fibers a) Fiber volume ratio should be 0.1-30%, preferably 0.1-10% And b) The thermal conductivity of the fibrous material should be as low as possible, preferably &lt;1 W / mK. is there. When high density fibers, such as glass fiber, are used in high volume ratios, composite materials also 0.9g / cm³May have densities ranging from. With proper selection of fiber diameter and / or material, for thermal conductivity It is possible to reduce the involvement of radiation and obtain greater mechanical intensity. For this The diameter of the fiber is a) 0.1-30 μm for non-metallized fibers and / or b) In the case of metallized fibers, preferably 0.1 to 20 μm Is. The involvement of radiation in thermal conductivity is due to IR opaque fibers such as carbon fiber. It can be further reduced by using PET fiber blackened with black. Mechanical strength is further influenced by the length and distribution of fibers in the airgel To. Fibers should be randomly or regularly contained, for example as individual fibers. Can be done. In this case, there are few fibers to ensure that a composite material of sufficient strength is obtained. Both should be 1 cm long. You can also use the web or mat, In the case of, a plurality of webs or mats may be overlapped. Stack in the selected direction In the case of the arranged mat, it is advantageous to change the selection direction for each layer. The composite can be hydrophobized by proper modification of the airgel pore surface. The present invention is also a method for producing a composite material of the present invention. a) Prepare the sol and b) Add fiber to the sol and add c) Convert the sol obtained in b) into a gel and d) The gel is subjected to a deformation treatment suitable for causing cracks in the gel in a specific manner. Average capacity 0.001mm³From 1 cm³Formed fiber-bonded fragments with The liquid present in the gel can be replaced before, during and / or after this deformation. Or do not replace, and e) Dry the deformed gel obtained in d) so that an airgel can be obtained. Provide a method including that. The starting material for step a) is a metal oxide compound suitable for the sol-gel method, especially silicon. And aluminum compounds (CJ Brinker, GW Scherer) , Sol-Gel Science, 1990, Chapters 2 and 3), for example Alkoxide of iodine or aluminum, water glass, organic polycondensate, etc. Based on lamin-formaldehyde resin (US Pat. No. US-A-5,08) 6,085), or based on resorcinol-formaldehyde resin Based on the thing (US Pat. No. US-A-4,873,218), or a mixture thereof To do. The sol is further granular or colloidal silicon oxide or oxide a. It may consist of luminium. It is preferable to use silicon compounds, especially water glass. I'm sorry. Sol particles have condensable functional groups on their surface. These groups are listed below in this document. It is described as a surface group. Typically from a compound of silicon or aluminum The sol particles are hydrophilic and have a hydroxyl group (OH). Alkoxy as a starting material Alkoxy groups (OR) from the manufacturing process may remain slightly when using Possibility (CJ Brinker, GW Scherer, Sol-Ge l Science, 1990, Chapter 10). IR opaque agents such as carbon black, titanium dioxide, iron oxide or di When zirconium oxide is added to the sol before gel production, the relationship of radiation to thermal conductivity You can reduce the amount given. Dyes and / or colored pigments may be added for coloring if desired. The fibers used in step b) are subject to the above findings. Fibers are suitable for improving their dispersibility or web wettability. Can be coated with a syrup. The coating improves the binding of the gel to the fibers Can also be used for. The sol-to-gel conversion (step c) is, for example, for silicon or aluminum. Hydrolysis and condensation of alkoxides, granular or colloidal silicon or Performed by gelling aluminum oxide or a combination of these methods Can be done. For the production of silicon-containing gels, for example, International Patent Application Publication WO 93/0 It is described in No. 6044. The production of organic gels is, for example, US Patent US-A- Described in 5,086,085 and US Pat. No. US-A-4,873,218 ing. If an aqueous sol is used in step a) and the pH is changed with a mineral acid, it contains an electrolyte. The sol should be washed with water until it is no longer present. The addition of fibers, especially for individual fibers, during gel formation, the sol is already highly viscous. It can also be done when it has reached a certain level but is not yet solid. In step d), a crevice was ideally formed over the entire area and surrounded by it. The gel is deformed to define the fibrous bonded pieces. For this, the song Raise the gel not only on the gel surface but also on the gel back surface (subface) in the same direction. Should be. This favorably rolls the gel or flexes This can be achieved by guiding around a deflecting roller. in particular Uniform fragments are obtained when deformed in two directions perpendicular to each other. Average volume of fragments when crevices are formed by guiding around the roll Selects roll diameter and gel hardness (eg by gel aging) It can be controlled in a specific way. To form the above average volume fragments The roll diameter is preferably 2-10 cm. The diameter of these rollers is small The average volume of the fragments is small, and the mechanical flexibility of the composite is high. To increase the hardness of the gel, age the gel obtained in step c) or d). Is advantageous. Gel aging is generally from 20 ° C to the liquid present in the gel. It is done at temperatures up to the boiling point of the body. For example, the liquid of the gel is water, and the gel matri Tsu Camphor tree₂If, the aging process is generally 20-90 ° C, preferably 1 minute to 48 hours at 20 to 70 ° C, pH 6 to 11, preferably 6 to 9. Especially, it takes from 15 minutes to 24 hours. The liquid present in the gel is subjected to at least one cleaning process (step d), followed by subsequent operations. Can be replaced with the same or other liquid suitable for drying in step e). It is advantageous to deform the gel during the liquid exchange in step d). Steps a) to d) are generally the temperature between the freezing point of the liquid present in the gel and 70 ° C. Degrees, but not above the boiling point of the liquid present in the gel. Advantageously, the gel obtained in step d) is dried below criticality to make an airgel composite. Can be formed. Drying process includes: e1) The gel obtained in step d) is further condensed between the surface groups on the surface of various pores. Sufficiently sufficient to substantially suppress and / or dry with the pore surface Sufficient to reduce capillary force by changing the contact angle with the liquid One or more so that a large proportion of gel surface groups are replaced by groups of surface modifiers React with more surface modifiers e2) Replace the liquid present in the gel if desired, and e3) The obtained gel is cooled to a temperature below the critical temperature of the liquid present in the gel, and 0. Dry at a pressure from .001 bar to the vapor pressure of this liquid at this temperature .. In step d), a liquid suitable for the above-mentioned subsequent treatment step must be used for cleaning. It doesn't become. For example, if the gel contains water, make the gel protic or non-proto The water content of the gel is 5% by weight, preferably 2% by weight. It is recommended to wash with. The organic solvents used are generally ethers, esters or ketones, as well as It is an aliphatic or aromatic hydrocarbon. Preferred solvents are methanol, etano Lu, acetone, tetrahydrofuran, ethyl acetate, dioxane, n-hexane, n-heptane and toluene. A mixture of the above solvents can also be used. The solvent must be substantially inert to the surface modifier used in subsequent steps. I. The surface modifier used in step e1) is a hydrophilic group or reactive surface group on the surface of the pores. Most are converted to hydrophobic surface groups or higher surface groups that are not suitable for condensation. As a result, further condensation between groups on different pore surfaces is suppressed and the pore walls Changes in the contact angle between the and the liquid meniscus to be dried Reduces capillary strength. The gel is silicon oxide gel, aluminum oxide gel or silicon aluminum oxide If it is a gel, the first surface group present is generally a group of formula MOH or MOR. In the equation, M is Al or Si and R is C.₁~ C₆-Alkyl, preferably me It is chill or ethyl. General formula R'_nMX_mBy the reaction with the surface modifier of The first surface group is MR'_nSubstituted with an inactive group of type. Where n and m are from zero It is a large integer, the sum of which corresponds to the valence of M. R'is hydrogen or non-hydrogen Reactive, organic straight chain, branched chain, cyclic, aromatic or heteroaromatic groups, eg C₁~ C₁₈-Alkyl, preferably C₁~ C₆-Alkyl, preferably methyl Or ethyl, cyclohexyl or phenyl; R'is independent, It may be equal to or different from the others, and may be cross-linked. In addition, X is a haloge , Preferably Cl, or the group -OR , -SR or -NR ₂And In these, R is linear or branched, equal or different, mono-. Or poly-substituted aliphatic group C₁~ C₁₈(Here 1 or more C H₂The groups are -CC-, -CH = CH-, -COO-, -O (C = O)-, SiR₂-, -CO-, may be replaced with phenylenediyl, and / also Is a maximum of every second CH₂Units may be exchanged with O or NR , this In them, R is phenyl, C₁~ C₁₈-Alkyl or benzyl) Or R is a benzyl or phenyl group (these are 1 to 5 groups) Substituents R', OH, OR', COOR', OCOR', SO₃H, SO₂Cl, F, Cl, Br, NO₂Or it may be replaced by CN); and the field of N In that case, each R is independently equal to or different from the others. m is at least 2 In some cases, each X is independent, equal to, different from, or crosslinked. doing. A mixture of surface modifiers can also be used. Equation R'_4-nSiCl_nOr R'_4-nSi (OR )_nTo use the silylating agent of Is preferable, n in the formula is 1 to 3, and R and R are defined above, respectively. It is a thing. Shirazans are also suitable. Methyltrichlorosilane, dimethyldic Lorosilane, trimethylchlorosilane, trimethylmethoxysilane or hexa It is preferable to use methyl disilazane. Preferably, this silylated gel is subjected to step e2) to remove the unconverted surface modifier. Protic or aprotic until essentially removed (residual level 1% by weight) Clean with a sex solvent. Suitable solvents are those described in step d). Similarly , The solvent described therein as preferred is also preferred in this case. In a special embodiment, in step e3), a fiber-reinforced surface-modified gel is applied at -30 to 2 Temperatures of 00 ° C, preferably 0-100 ° C, and 0.001-20 bar, preferred Dry at 0.01-5 bar, especially preferably 0.1-2 bar. 2 Temperatures above 00 ° C and / or pressures above 20 bar are also easily possible. However, they involve unnecessary effort and bring no advantage. Drying is generally This is done until the residual solvent content is less than 0.1% by weight. For a suitable drying process, For example, contact drying and convection drying are included. In addition, gel drying is marked by the adoption of dielectric drying methods, such as microwave drying. Can be promoted. For this purpose, after surface modification, the solvent is required in step e2). The effective microwave absorber is a solvent such as water, ethanol or preferred Or replace with acetone. The gel is then quickly dried in a microwave dryer. be able to. Solvent exchange time and drying time are essentially determined by the diffusion of solvent or solvent vapor. To be determined, solvent exchange and drying should be done on gels with a thickness of 0.5-5 mm. Is particularly advantageous. SiO of the present invention₂A method of manufacturing airgel composites a) Water glass aqueous solution (SiO)₂Concentration is generally 10% by weight, preferably 7% by weight %) Is adjusted to pH 3 with, for example, an acidic ion exchange resin or mineral acid, and then Base to the obtained silicic acid, generally NH₄OH, NaOH, KOH, Al (O H)₃And / or add colloidal silica, b) Add fiber and c) Polycondensate silicic acid d) The gel is subjected to a deformation treatment suitable for causing cracks in this gel in a specific manner. And the average capacity is 0.001mm³From 1 cm³Form fiber-bonded fragments with Allow the gel to have a water content of 5 weight before, during and / or after this deformation. Wash with organic solvent until% e1) The gel obtained in step d) is reacted with a silylating agent to cause it to react. e2) If desired, the residual level of the unconverted silylating agent of the silylated gel is 1. Wash with organic solvent until weight%, and e3) The silylated gel obtained in step e1) or e2) was -30 to 200 ° C and 0. Dry at .001 ~ 20bar The method including the above is preferable. Step a) is preferably carried out using an acidic ion exchange resin. The composite material thus obtained is, for example, when trimethylchlorosilane is used. As described above, when the surface group imparted by surface modification is hydrophobic, it is hydrophobic. Sparse Water content is then substantially reduced, for example by release or partial pyrolysis. Can be done. Alternatively, in step e), the gel obtained in step d) is present in, for example, the gel. Converts the liquid to a supercritical state, and then flushes this liquid from the solid at supercritical temperature. The airgel composite is dried by removing it by vaporizing it. Can be formed. To do this, a liquid suitable for drying, such as liquid CO₂Alternatively, methanol shall be used for the exchange in step d). CO₂From Typical methods for supercritical drying are, for example, US Pat. No. US-A-4,610,8 No. 63 or Bommel MJ, de Haan AB, Journ al of Materials Science, 29 (1994), 943 -948, and the method from methanol is European Patent Gazette EP-B-039607 It is described in No. 6 or WO 93/06044 of the International Patent Application Publication No. To finally obtain a hydrophobic airgel, between steps d) and e), if desired. After exchanging the solvent, the gel can be reacted with a surface modifier that makes the surface hydrophobic. To. If necessary, do not replace the solvent with a liquid suitable for drying again following this step. You may have to. Suitable for this purpose are, for example, for surface modification. The above-mentioned substances and methods. But advantageously, this reaction is carried out in the gas phase after drying. You can also do it. The advantage of the method of the present invention over the deformation of pre-dried fiber reinforced airgel is that the fragments are Uniform formation and deformation in the gel state typically shed fragments There is no such thing. The composite material thus obtained is visually uniform due to the similar size of the fragments. To. The flexural rigidity of the composite material depends on the selection of the fiber material to be used and the degree of bending after gel formation. It can be changed depending on the degree. The thin aerogel mat of the present invention, for example a suitable three Insertion, gluing or suitable mechanical bonding, eg clipping or sewing They can be reinforced by joining them together. The surface of the composite material Materials known to those of skill in the art, such as polymer films, paper, web or woven fabrics May be laminated with. The composites of the present invention also have low thermal conductivity suitable for using them as insulation. Tsu. When using transparent fibers, such as fiberglass, the mats of the invention still remain. It is translucent and can therefore be used as a transparent insulation. Textile material and distribution Use the right choices to change translucency on the one hand and achieve decorative effects on the other can do. In addition, they have a low speed of sound and are compared to monolithic aerogels. Since it has a high sound deadening capacity, they can be used directly as a sound absorbing material or in the form of a resonance absorber. Can be used in. Specific variation in the average volume of fragments, and thus the number of fissures Therefore, the porosity of the material, and therefore the degree of sound deadening, can be increased. A brief description of the drawing Figure 1 shows pore 1, liquid meniscus and pores almost half-filled with liquid 2 and vapor 4. The contact angle θ with the wall 3 and the radius r of the pores are schematically shown. Example 1: Using tetraethyl orthosilicate (TEOS) by the following method Manufactured: 100 ml TEOS, 100 ml ethanol, 7.98 ml distilled water, and And 0.33 ml of 1M HCl were added together and refluxed for 1.5-2 hours. 10 parts of this sol is 1 part of 0.5M NH₄Mix with OH solution and in Petri dish, 50% 0.9dtex and 1.7dtex TREVIRA (registered) respectively Trademark) 290 (Density 15 kg / m³, 150 stitches (stitches) / cm²And knee Pour onto a polyester web consisting of (dollar processing). This amount just covers the fibers It was enough for me. The gelation time was about 20 minutes. During that period, try The charge was kept in a sealed state. Age of gel by heating at 50 ° C for 24 hours I went to The gel plate thus produced is then placed in a glass cylinder with a diameter of 3 cm. Wrapped around. The plate is once with the front side facing the cylinder, and the back side is a cylinder. It was wrapped around the cylinder once towards the dar. Then turn the plate 90 ° It was rolled and this operation was repeated once more. Aging gel cooled to room temperature is charged in ethanol and then at 50 ° C. Heated for 1 hour. Do this twice with fresh ethanol, then with n-hexane 1 Repeated times. The n-hexane is then changed 3 times and the sample is placed at 50 ° C for another 24 o'clock. Saved for a while. The gel plate thus formed is then glassed with a diameter of 3 cm. For the linder, first turn the front side of the plate toward the cylinder, then the back side of the plate. I wrapped it around Linder. Then rotate the gel plate 90 ° and this The operation was repeated. This wet gel was then subjected to 10 wt% trimethylchlorosilane. It was mixed with (TMCS) and stored at 50 ° C for 24 hours. Then the TMCS balance is 50 The cells were washed and removed twice with n-hexane at ° C for 1 hour each. Then, dry for 24 hours in 3 steps of 37 ° C, 50 ° C and 140 ° C. went. This airgel composite has a fragment capacity of 3.5 mm³Have. Thermal conductivity Measured by the hot wire method (eg O.Ni)<img file="JPH10504792A_D0002.tif" />ke, High Temperatures-High Pressures, See Vol.21,267-274 (1989)). The result is a value of 22mW / mK Met. Modulus was measured by the 3-point bending method (eg GW Schere) r, SAPardenek, RMSwiatek, J.Non-Cry See stalline Solids, Vol.107, 14-22 (1988) Teru). The result is a value of 1.3MPa, which is extremely high compared to the prior art airgel. It was a flexible aerogel mat. This aerogel mat does not break at a constant tension during the 3-point bending test and has a high negative value. It was only irreversibly deformed by the load. Example 2: An experiment was performed in the same manner as in Example 1, but a glass cylinder with a diameter of 10 cm. Was used. This airgel composite has a fragment capacity of 8 mm³Had. Thermal conductivity And the elastic modulus was measured in the same manner as in Example 1. The obtained thermal conductivity value is 20m W / mK, elastic modulus was 2 MPa. This aerogel mat does not break at a constant tension during the 3-point bending test and has a high negative value. It was only irreversibly deformed by the load. Example 3: Waterglass was used as the basis for the production of aerogel mats by the following methods: Basic weight 300g / m²And 3mm thick fiberglass web (Polymat- PolyMat-Glasnadelmatte Thailand (From Pu G300, Weltheim, Schuller) was calcined at 50 ° C for 1 hour. 1 l sodium water glass solution (8 wt% SiO₂Contains, Na₂O: Si O₂Weight ratio 1: 3.3), 0.5 liter of acidic ion exchange resin (sulfonic acid group) Styrene-divinylbenzene copolymer with Duolite, This aqueous solution has a pH of 2.7, along with a registered trademark) (commercially available under the name C20). Stirred until reached. Next, the ion exchange resin is filtered off, and the aqueous solution is 1M NaO. The pH was adjusted to 4.8 with H solution. Put the web in a mold and pour the above sol on top of it Covered the entire web with. Then seal the mold and place it in the drying cabinet at 85 ° C at 5 o'clock. Saved for a while. The gel plate thus produced is then placed in a glass cylinder with a diameter of 10 cm. Wrapped around. Plate once with the front side facing the glass cylinder, and the back side Wrapped around the cylinder once towards the glass cylinder. Then pre This operation was repeated once more by rotating the machine 90 °. The mat is then washed with acetone until the water content is less than 0.5% by weight. did. Wet gel is mixed with 10 wt% trimethylchlorosilane (TMCS) and Stored at room temperature for 24 hours. It was then washed 6 more times with acetone. Dry In two steps, ie 50 ° C and pressure 850 mbar for 24 hours, then 14 It was carried out at 0 ° C. and a pressure of 50 mbar for 12 hours. The density of this composite is 0.25 g / cm³Met. Thermal conductivity and elastic modulus The measurement was carried out in the same manner as in the case of Example 1. The measured value of thermal conductivity is 18mW / mK, elastic modulus Was 2 MPa. This aerogel mat does not break at a constant tension during the 3-point bending test and has a high negative value. It was only irreversibly deformed by the load.