DE112017001567T5 - A rapid production process for an airgel with a microemulsion precursor - Google Patents

Abstract

A rapid production process for an airgel having a microemulsion as a precursor, comprising: 1. measuring a specific water-soluble silicon source to produce a certain amount of an aqueous solution and adding a certain amount of a surfactant and a cosurfactant which are completely dissolved; 2. Measuring a specific active organosilicon compound and a secondary oil phase, which are added to the above solution and stirred for a certain time at high speed, so that a semitransparent, homogeneous and stable mixed liquid, d. H. forms a microemulsion; 3. combination of the microemulsion with an inorganic additive and a nonwoven fabric, which forms a solid phase after a certain time and you can win by aging and drying under normal pressure or supercritical drying a nonwoven airgel composite material. The present production process is novel, the cost of the raw materials is low, and the range of application is wide, both a normal pressure drying method and supercritical drying can be used, and the obtained material has very good heat insulating properties and a high strength structure and shrinkage rate for long-term use is low.

Description

Technical area

The present invention relates to a rapid production process for an airgel and its composite materials with a microemulsion precursor, and more particularly to a rapid production process for a hydrophobic airgel and its composite materials, wherein surface hydrophobing and modification is performed in a microemulsion system.

General state of the art

Silica aerogels are novel, lightweight and highly porous materials with air as the dispersion medium, which are formed by a collection of nanometer-sized particles. Their pore content is 80-99%, their typical pore size is 1-100 nanometers, and they have advantages such as low thermal conductivity, low acoustic impedance, low refractive index and high absorbency. From a chemical, thermophysical, optical, acoustical and electrical point of view, they have unique properties and have a broad application perspective in key areas such as aerospace, defense, communications, medical, materials science, electrical engineering, metallurgy and the chemical industry. In 2007, the English Times celebrated silica aerogels as "miracle materials capable of changing the world". Precisely because they have such a huge application potential, more and more scientists from all over the world are trying to develop manufacturing processes for different types of silica aerogels. If one summarizes the existing patents and documents, one can subdivide the state of the art in the production of silica aerogels by the drying method substantially in the two types of drying under normal pressure and a supercritical drying; according to the type of silicon source essentially in the two types of inorganic and organic silicon sources; and according to the type of surface modification substantially in the two types of modification before drying and the modification after drying. The usual manufacturing processes essentially include the following: 1. hydrolysis of the silicon source; 2. Sol-hydrophobing; 3. sol-gel process (combination with other materials); 4. Aging; 5. Exchange of the solvent in the gel; 6. gel surface modification (hydrophobization treatment); 7. drying process (supercritical drying or drying under normal pressure); 8. Airgel surface modification (hydrophobing treatment). Individual steps of the processes listed above do not have to be mandatory steps in different manufacturing processes and additional intermediate steps may be necessary in some manufacturing processes. In a typical production process using an organic silicon source, tetraethylorthosilicate or tetramethylorthosilicate (and corresponding polymers) are used as the silicon source and ethanol or a mixed liquid of ethanol and water as the solvent, an acid is added to effect hydrolysis, a base is added to obtain the hydrolyzate liquid is allowed to gel faster, solidification is brought about by aging and the liquid in the gel is exchanged several times with an organic solvent. Subsequently, a surface hydrophobization treatment of the gel is carried out by means of reactive silane reagents such as chlorotrimethylsilane, hexamethyldisilazane or hexamethyldisiloxane, and a hydrophobic silica airgel is obtained by supercritical drying or drying under normal pressure. The raw materials used in such processes are generally relatively expensive and also toxic, the technology is complicated, the consumption of organic solvents is large, the safety is low and the mass production and application of this technology is limited. See the patents CN101671030B . CN101264891B . US5830387 . CN100384726C . CN100400153C , In a typical production process for a silica airgel with an inorganic silicon source, water glass is used as the silicon source, an acidic silica sol is obtained with the aid of an ion exchange resin, a base is added thereto, and a gel is formed from the silica sol by polycondensation. Thereafter, the gel is washed with water to remove the electrolyte, or after the formation of the gel, repeated washing with water is performed to remove the electrolyte; Subsequently, with an organic solvent on the hydrogel, a multiple exchange is carried out so that the water content of the gel is reduced to a certain value, by means of reactive silane reagents such as chlorotrimethylsilane, hexamethyldisilazane or hexamethyldisiloxane a surface hydrophobic treatment of the gel is carried out and then obtained by supercritical drying or Drying under normal pressure a hydrophobized silica airgel. See the patents WO96 / 22942 ( CN1181053A ) WO97 / 17288 ( CN1087271C ) WO97 / 48642 ( CN1105679C ) WO98 / 23367 ( CN1101725C ) EP-A-0658513 . CN1636871B . CN1241953B . CN101844771A , Such processes are cumbersome to handle, the production cycle is long and in the manufacturing process, large amounts of saline wastewater. In a typical post-modification process, in general, the above-cited Sol - Gel - aging - exchanged used and dispenses with a surface modification with silane-based modifying liquids, wherein after a supercritical drying by means of the method of gassing with a silylating reagent to the airgel, a surface treatment is performed. See the patents CN1317188C . US6005012 . US5738801 and others, with this method often leaving relatively strong odors from the silane reagents or their decomposition products.

A typical pre-modification process comprises two methods: in one, after gelation, a surface modification is performed by dipping in a silylation reagent, whereby the consumption of the organic reagent is usually relatively large and takes a long time; the other is a method for a self-hydrophobing gel generally adding silylation reagents such as methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, etc. in the process of preparing the sol. These silylating reagents are hydrolyzed under the action of an acidic or basic catalyst by the interaction of the hydrophobic Group containing hydrolysis products with the sol particles of other silicon sources produced by hydrolysis polycondensation the hydrophobic groups are connected to the particle surfaces and under the action of a basic catalyst by polycondensation, a gel is produced, which is then obtained by a drying process, a hydrophobic silica airgel. See the patents CN100372765C . CN100398492C . CN101372337B . WO2005 / 110919 ( CN1984843A ) CN101450852A . CN101439958A . CN101973752A . US8663739B2 , Such processes avoid the heavy use of organic reagents, but prior to gelling, the surfaces of the sol particles are enveloped by large amounts of hydrophobic groups, often resulting in mutual repulsion between the particles and limiting the gelation process. Even if various basic catalysts are added, the gelation process is greatly prolonged as opposed to non-participation of hydrophobic groups, such as in patent CN100372765C where a time of 4 hours and more is needed for gelation; the strength of the gel formed is comparatively low, and it is necessary for a long aging, the patent CN100372765C 24 hours. Some inventors also attempt to circumvent the processes of pre-modification or post-modification as well as solvent exchange by the addition of surfactants, such as in the patents CN103204666A and CN103496707A to obtain a hydrophilic or poorly hydrophobic xenogel whose density is relatively high and whose porosity and specific surface area are relatively low. In summary, the cost of producing silica aerogels with organic silicon sources is relatively high, the consumption of organic solvents is high and the safety is relatively low; inorganic siliceous sources are noted for their low price, but still suffer from problems such as difficult handling and long production cycle. Methods for self-hydrolyzing gels can shorten the production cycle and avoid the heavy use of organic reagents, but currently the cost of their raw materials is relatively high and limits the use of these methods. The patent CN104003406A discloses a method for producing an airgel powder, characterized in that a microemulsion prepared from a sol-silicon source, an oil phase, a surfactant and a cosurfactant is used to prepare a wet gel which is treated by aging, washing, solvent exchange and surface modification in which, after drying under normal pressure, a hydrophobized silica airgel powder is obtained. The differences of this method to the above process of producing an airgel from an inorganic silicon source reside in the use of a microemulsion process to produce a wet gel, the later process still being a traditional elaborate treatment process, consuming large amounts of organic solvents in the wash and exchange process and in addition a surface modification must be performed, whereby the whole process takes a relatively long time. Because of this, the present invention is presented.

Brief description of the invention

With respect to the respective features and deficiencies of the above prior art processes, the present invention provides a rapid production process for an airgel having a microemulsion precursor, wherein the main raw material of the process is a water-soluble inorganic silicon source, and a process of microemulsion their self-hydrophobization is realized, thus effectively avoiding the shortcomings of prior self-hydrophobing processes, shortening the entire production cycle, avoiding complicated exchange and surface modification processes, and obtaining a high temperature resistant silica airgel material.

1. (1) Herstellung einer Mikroemulsion: eine bestimmte Menge einer wasserlöslichen Siliziumquelle wird mit Wasser vermischt und es wird eine bestimmte Menge eines Tensids und eines Cotensids hinzugegeben; alles wird in einem Mixer mit hoher Geschwindigkeit verrührt und dann langsam eine oder mehrere siliziumorganische Verbindungen sowie sekundäre Ölphasen hinzugegeben, bis man eine semitransparente und homogene Mikroemulsion erhält.
2. (2) Herstellung eines Gels: an der in Schritt (1) gewonnenen Mikroemulsion wird über einen bestimmten Zeitraum und/oder unter Zugabe einer entsprechenden Menge eines sauren oder basischen Katalysators eine beschleunigte Gelierung durchgeführt.
3. (3) Alterungs- und Verfestigungsprozess: an dem in Schritt (2) gebildeten Gelmaterial wird innerhalb eines bestimmten Zeitraums und/oder unter Erwärmung eine Alterung durchgeführt.
4. (4) überkritische Trocknung oder Trocknung unter Normaldruck: an dem in Schritt (3) gewonnenen Gel wird eine überkritische Trocknung oder eine Trocknung unter Normaldruck durchgeführt, worauf man ein hydrophobes Siliziumdioxid-Aerogel erhält.

In order to achieve the above object, the present invention is realized via the following technical solutions:
A rapid production process for an airgel with a microemulsion precursor, characterized by comprising the steps of:

1. (1) Preparation of a microemulsion: a certain amount of a water-soluble silicon source is mixed with water, and a certain amount of a surfactant and a cosurfactant are added thereto; Stir everything in a blender at high speed and then slowly add one or more organosilicon compounds as well as secondary oil phases until a semitransparent and homogeneous microemulsion is obtained.
2. (2) Preparation of gel: Accelerated gelation is carried out on the microemulsion obtained in step (1) for a certain period of time and / or with the addition of an appropriate amount of an acidic or basic catalyst.
3. (3) Aging and solidification process: Aging is performed on the gel material formed in step (2) within a certain period of time and / or under heating.
4. (4) supercritical drying or drying under normal pressure: on the gel obtained in step (3), a supercritical drying or drying is carried out under normal pressure, whereupon a hydrophobic silica airgel is obtained.

The water-soluble silicon source in step (1) is water glass, an acidic silica sol with water as solvent, a basic silica sol with water as solvent, lithium methyl silicate, sodium methyl silicate, potassium methyl silicate, lithium silicate, lithium metasilicate, sodium silicate, sodium metasilicate, potassium silicate or potassium metasilicate or a combination of several this;
the surfactant in step (1) is sodium dioctylsulfosuccinate, sodium laurylsulfonate, sodium dodecylbenzenesulfonate, sodium laurylsulfate, fatty alcohol polyoxyethylene ether sodium sulfate, polysorbate 60, polysorbate 80, Span 20, or polyethylene glycol monooleate or a combination of any of these;
the cosurfactant in step (1) is acetone, methyl butanone, methyl isobutyl ketone, ethyl acetate, methanol, ethanol, ethylene glycol, 1-propanol or 2-propanol or a combination of any of these;
the organosilicon compound in step (1) is hexamethyldisiloxane, hexamethyldisilazane, dimethyldiethoxysilane, monomethyldiethoxymonohydrosilane, methyltriethoxysilane, methyltrimethoxysilane, polymethyltriethoxysilane, polymethyltrimethoxysilane, methylhydroxysilicone oil, hydroxyhydrogensilicone oil, methyltrifluoropropylsilicone oil or methylvinylsilicone oil or a combination of any of these;
and the secondary oil phase in step (1) is n-hexane, cyclohexane, n-pentane or liquid paraffin, or a combination of several of these.

The acidic catalyst in step (2) is hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, clover acid, acetic acid or ethanedioic acid or a combination of several of these; the basic catalyst in step (2) is ammonia water, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, sodium carbonate or potassium carbonate or a combination of several of these.

Before an acidic or basic catalyst is added in step (2), an appropriate amount of an inorganic additive is added to the microemulsion obtained in step (1), and after uniform mixing, the microemulsion is entrained by spraying or complete dipping a fibrous material, wherein the microemulsion after uniting into a gel forms a unit with the fiber.

The fibrous material is a glass fiber, an aluminosilicate fiber, a mullite fiber, a basalt fiber, a polyester fiber, a polyacrylonitrile fiber, a carbon fiber or a viscose fiber, or a combination of a plurality of them; the inorganic additive is titanium dioxide, ferric oxide, ferrous oxide, aluminum oxide, magnesium oxide, zinc oxide, aluminosilicate, magnesium silicate, calcium silicate, zinc silicate, zinc borate, magnesium hydroxide, aluminum hydroxide or iron (III) hydroxide oxide or a combination of several of these.

The period of time for aging in step (3) is 10 minutes to 10 hours and the aging temperature is 10 to 75 ° C. In the aging process in step (3), a certain amount of organic solvent is added, wherein the organic solvent is methanol, ethanol or acetone or a combination of several of them.

The drying temperature in step (4) under normal pressure conditions is 50-200 ° C and under the conditions of supercritical drying with carbon dioxide 30-65 ° C; under the conditions of supercritical drying with ethanol, the drying temperature is 220-250 ° C.

Compared with the methods of the prior art, the present invention has the following advantages: 1. With a water-soluble silicon source as the main silicon source, the cost remains low and there are prospects for mass production; 2. the use of the microemulsion process to produce a precursor firstly completes the hydrophobing process and secondly, a gel can be formed more quickly and the influence of the hydrophobizing reagents on the gelation process is reduced; 3. The handling process is short and fast, a strong consumption of organic Solvent is avoided and the entire manufacturing process is shortened; 4. The process is novel and unique, completely combining the particularities of the microemulsion method and the sol-gel process, overcoming the previously unique sol-gel process in gel production and providing one for the production of hydrophobic silica aerogels new approach ready; 5. The microemulsion prepared in this process has very good wettability and permeability, it is well compatible with various inorganic additives and fiber materials, and the airgel material obtained therefrom has high mechanical strength and temperature resistance.

list of figures

• 1 shows a representation of a water phase with an inorganic silicon source and an oil phase with an organosilicon compound, which form an entangled three-dimensional structure at the micro level.
• 2 Figure 4 shows a representation of the microstructure of an airgel obtained with the present invention.

embodiments

1. 1. Mikroemulsionsverfahren zur Herstellung eines Aerogels bei Trocknung unter Normaldruck: Zu 500 ml basischem Kieselsol werden bei gleichzeitigem Rühren mit hoher Geschwindigkeit nacheinander 650 ml Wasser, 30 g Natriumdioctylsulfosuccinat, 20 g Azeton, 350 g n-Hexan und 150 g Methyltriethoxysilan hinzugegeben und mit hoher Geschwindigkeit verrührt, bis man eine semitransparente homogene Mikroemulsion erhält, der eine kleine Menge wässrige Schwefelsäurelösung zugegeben wird, bis der pH-Wert 8 eingestellt ist; daraufhin wird 10 min mit hoher Geschwindigkeit verrührt, anschließend die Form umgedreht und für 40 min ruhen gelassen, worauf die Mikroemulsion in ein semitransparentes weißblaues Gel umgewandelt wird; das Gel wird in Ethanol bei 60°C für 1 h gealtert, wobei im Alterungsprozess durch eine effektive Abdichtung und Hinzugabe einer kleinen Menge Ethanol verhindert wird, dass das Gel aufgrund einer Verflüchtigung des Lösungsmittels bricht. Nach Beendigung der Alterung wird das Gel in einem Trockenluftofen bei 150°C für 2 h getrocknet, worauf man einen Block aus hydrophobem Siliziumdioxid-Aerogel mit einer Dichte von etwa 110 mg/cm³ erhält, dessen Mikrostruktur auf dem Scan des Rasterelektronenmikroskops in 2 zu sehen ist.
2. 2. Mikroemulsionsverfahren zur Herstellung eines Aerogel-Faserfilzes - überkritische Trocknung mit Kohlenstoffdioxid: Zu 500 ml Wasserglas werden bei gleichzeitigem Rühren mit hoher Geschwindigkeit nacheinander 800 ml Wasser, 36 g Natriumlaurylsulfat, 20 g Ethylazetat, 10 g 2-Propanol, 350 g n-Hexan und 200 g Polymethyltriethoxysilan hinzugegeben und mit hoher Geschwindigkeit verrührt, bis man eine semitransparente homogene Mikroemulsion erhält, der eine kleine Menge wässriger Schwefelsäurelösung zugegeben wird, bis der pH-Wert 7 eingestellt ist, es wird 10 min mit hoher Geschwindigkeit verrührt und die Mischung für eine weitere Verwendung bereitgehalten. Ein Stück Glasfaser-Nadelfilz mit 30 cm Länge, 30 cm Breite, 10 mm Dicke und einer Dichte von 80 kg/m³ wird flach in eine vorbereitete Form gelegt, anschließend wird die vorbereitete Mikroemulsion gleichmäßig in die Form gegossen, bis der Faserfilz mit der Flüssigkeit getränkt ist und der Deckel der Form aufgesetzt, um ein Verflüchtigen zu verhindern. Nach 30 min Ruhenlassen hat sich ein Glasfaser-Gel-Verbundmaterial gebildet; das Gelmaterial wird in Ethanol gelegt und bei 60°C für 5 h gealtert, wobei das Ethanolvolumen das 5fache des Volumens des Gelmaterials beträgt; nach Beendigung der Alterung wird das Gelmaterial in einen Extraktor mit überkritischem Kohlenstoffdioxid gegeben, der Druck wird auf 10 MPa und die Temperatur auf 40°C eingestellt, nach 6 h Trocknung wird der Druck beibehalten und die Temperatur gesenkt und zuletzt erhält man ein hydrophobes, hochfestes Faserfilz-Siliziumdioxid-Aerogel-Verbundmaterial, das bei 25°C einen Wärmeleitkoeffizienten von 0,0155 W/mK aufweist.
3. 3. Mikroemulsionsverfahren zur Herstellung eines verstärkten Aerogel-Faserfilzes - überkritische Trocknung: Zu 300 ml Wasserglas und 200 ml Natriummethylsilikat werden bei gleichzeitigem Rühren mit hoher Geschwindigkeit nacheinander 600 ml Wasser, 36 g Natriumlaurylsulfat, 20 g Azeton, 10 g 2-Propanol, 300 g n-Hexan, 200 g Polymethyltriethoxysilan und 50 g Methylhydroxysilikonöl hinzugegeben und mit hoher Geschwindigkeit verrührt, bis man eine semitransparente homogene Mikroemulsion erhält, der eine kleine Menge wässrige Schwefelsäurelösung zugegeben wird, bis der pH-Wert 7 eingestellt ist, und anschließend werden 15 g Titandioxid, 12 g Aluminiumhydroxid, 12 Magnesiumhydroxid und 12 g Eisen(III)-hydroxidoxid hinzugegeben und mit hoher Geschwindigkeit für 10 min verrührt und für eine weitere Verwendung bereitgehalten. Ein Stück Glasfaser-Mullitfaser-Verbundnadelfilz mit 30 cm Länge, 30 cm Breite, 10 mm Dicke, einer Dichte von 100 kg/m³ und einem Gewichtsverhältnis von Glasfaser und Mullitfaser von 7:3 wird flach in eine vorbereitete Form gelegt, anschließend wird die vorbereitete Mikroemulsion gleichmäßig in die Form gegossen, bis der Faserfilz mit der Flüssigkeit getränkt ist, und der Deckel der Form wird aufgesetzt, um ein Verflüchtigen zu verhindern. Nach 40 min Ruhenlassen hat sich ein Gel-Verbundmaterial aus einem anorganischen Additiv und einer Faser gebildet; das Gelmaterial wird in Ethanol gelegt und bei 60°C für 5 h gealtert, wobei das Ethanolvolumen das 5fache des Volumens des Gelmaterials beträgt; nach Beendigung der Alterung wird das Gelmaterial in einen Extraktor mit überkritischem Kohlenstoffdioxid gegeben, der Druck wird auf 12 MPa und die Temperatur auf 50°C eingestellt, nach 6 h Trocknung wird der Druck beibehalten und die Temperatur gesenkt, und zuletzt erhält man ein hydrophobes, verstärktes Faser-Siliziumdioxid-Aerogel-Verbundmaterial mit einer relativ homogenen Verteilung des organischen Additivs, das bei 25°C einen Wärmeleitkoeffizienten von 0,0186 W/mK aufweist, bei einer Durchschnittstemperatur von 500°C einen Wärmeleitkoeffizienten von 0,059 W/mK aufweist, dessen Schrumpfrate bei 800°C innerhalb von 24 h weniger als 2 % beträgt und das sehr gute Anwendungseigenschaften bei hohen Temperaturen besitzt. Die vorliegende Erfindung stellt ein Schnellherstellungsverfahren für ein hydrophobes Aerogel und dessen Verbundmaterialien bereit, das eine Mikroemulsion als Prekursor verwendet und mit geringen Kosten verbunden ist. Bei einer Mikroemulsion bilden zwei sich nicht ineinander lösende Flüssigkeiten unter der Wirkung eines Tensids und eines Cotensids spontan ein homogenes und transparentes, thermodynamisch stabiles disperses System. Bei den beiden sich nicht ineinander lösenden Dispersionsmedien werden durch die amphiphilen Moleküle des Tensids winzige Räume aufgespalten und Mikroreaktoren gebildet, deren Größe im Nanometerbereich gesteuert werden kann, wobei die Reaktanten bei der Reaktion im System Partikel einer festen Phase erzeugen. Da die Mikroemulsion die Partikelgröße und Stabilität des Nanomaterials genau steuern und Prozesse wie Keimbildung, Wachstum, Ansammlung und Vereinigung begrenzen kann, sind die gebildeten Nanopartikel von einer Tensidschicht umhüllt und bilden eine bestimmte Struktur kondensierter Materie.

In the following, the present invention will be described in detail in connection with the concrete embodiments, but the scope of the present invention is not limited thereto.

1. 1. Microemulsion process for the preparation of an airgel under normal pressure drying: 650 ml of water, 30 g of sodium dioctylsulfosuccinate, 20 g of acetone, 350 g of n-hexane and 150 g of methyltriethoxysilane are added in succession to 500 ml of basic silica sol in high speed Stir the speed until a semitransparent homogeneous microemulsion is obtained, to which is added a small amount of aqueous sulfuric acid solution until the pH is 8; then stirred for 10 minutes at high speed, then inverted and allowed to rest for 40 minutes, whereupon the microemulsion is converted to a semi-transparent white-blue gel; the gel is aged in ethanol at 60 ° C for 1 h, during the aging process by effectively sealing and adding a small amount of ethanol to prevent the gel from breaking due to volatilization of the solvent. After completion of the aging, the gel is dried in a dry air oven at 150 ° C for 2 h, followed by a block of hydrophobic silica airgel having a density of about 110 mg / cm ³ , whose microstructure on the scan of the scanning electron microscope in 2 you can see.
2. 2. Microemulsion process for producing an airgel fiber felt - supercritical drying with carbon dioxide: To 500 ml of water glass while stirring at high speed in succession 800 ml of water, 36 g of sodium lauryl sulfate, 20 g of ethyl acetate, 10 g of 2-propanol, 350 g of n-hexane and 200 g of polymethyltriethoxysilane are added and stirred at high speed until a semitransparent homogeneous microemulsion is obtained, to which a small amount of aqueous sulfuric acid solution is added until the pH is adjusted to 7, stirred at high speed for 10 minutes, and the mixture is stirred for a while further use. A piece of fiberglass needled felt 30 cm long, 30 cm wide, 10 mm thick and 80 kg / m ^{3 in} density is placed flat in a prepared mold, then the prepared microemulsion is poured evenly into the mold until the fiber felt with the Liquid is soaked and the lid of the mold placed on to prevent volatilization. After resting for 30 minutes, a glass fiber-gel composite has formed; the gel material is placed in ethanol and aged at 60 ° C for 5 h, the ethanol volume being 5 times the volume of the gel material; after aging, the gel material is placed in an extractor with supercritical carbon dioxide, the pressure is set at 10 MPa and the temperature at 40 ° C, after 6 h drying, the pressure is maintained and the temperature is lowered and finally obtained a hydrophobic, high-strength Felt-silica composite airgel composite having a coefficient of thermal conductivity of 0.0155 W / mK at 25 ° C.
3. 3. Microemulsion process for producing a reinforced airgel fiber felt - supercritical drying: To 300 ml of waterglass and 200 ml of sodium methyl silicate with simultaneous stirring at high speed successively 600 ml of water, 36 g of sodium lauryl sulfate, 20 g of acetone, 10 g of 2-propanol, 300 g n-hexane, 200 g of polymethyltriethoxysilane and 50 g of methylhydroxy-silicone oil are added and stirred at high speed until a semitransparent homogeneous microemulsion is added, to which is added a small amount of aqueous sulfuric acid solution until the pH is adjusted to 7, and then 15 g of titanium dioxide , 12 g of aluminum hydroxide, 12 mg of magnesium hydroxide and 12 g of iron (III) hydroxide oxide and stirred at high speed for 10 min and kept ready for further use. A piece of fiberglass-mullite fiber composite needle felt 30 cm long, 30 cm wide, 10 mm thick, 100 kg / m ^{3 in} density and 7: 3 weight ratio of glass fiber and mullite fiber is placed flat in a prepared form, then the poured microemulsion uniformly poured into the mold until the fiber felt is soaked with the liquid, and the lid of the mold is placed to prevent volatilization. After resting for 40 minutes, a gel composite of an inorganic additive and a fiber has formed; the gel material is placed in ethanol and aged at 60 ° C for 5 h, the ethanol volume being 5 times the volume of the gel material; after aging, the gel material is placed in an extractor with supercritical carbon dioxide, the pressure is adjusted to 12 MPa and the temperature to 50 ° C, after 6 h drying, the pressure is maintained and the temperature is lowered, and finally a hydrophobic, reinforced fiber-silica-airgel composite material having a relatively homogeneous distribution of the organic additive, which has a coefficient of thermal conductivity of 0.0186 W / mK at 25 ° C, at an average temperature of 500 ° C has a heat transfer coefficient of 0.059 W / mK, the Shrinkage rate at 800 ° C within 24 h is less than 2% and has very good application properties at high temperatures. The present invention provides a rapid production process for a hydrophobic airgel and its composites using a microemulsion precursor and at a low cost. In the case of a microemulsion, two liquids which do not dissolve into one another spontaneously form a homogeneous and transparent thermodynamically stable dispersed system under the action of a surfactant and a cosurfactant. In the two non-dissolving dispersion media, tiny spaces are split by the amphiphilic molecules of the surfactant and microreactors are formed whose size can be controlled in the nanometer range, the reactants producing particles of a solid phase upon reaction in the system. Since the microemulsion can precisely control the particle size and stability of the nanomaterial and limit processes such as nucleation, growth, accumulation and association, the nanoparticles formed are enveloped by a surfactant layer and form a specific condensed matter structure.

In the present invention, by the addition of surfactants and cosurfactants and aided by high-speed stirring, the aqueous solution of the water-soluble silicon source with the non-water-soluble organosilicon compound and the secondary oil phase forms a homogeneous and stable microemulsion system, the water phase containing the inorganic phase Silicon source and the oil phase with the organosilicon compound on the micro-level form an entangled three-dimensional structure, as in 1 and the surfactant and the cosurfactant form a dynamic boundary between the two phases, after a certain time or accelerated by an adjustment of the pH and temperature of the system, the inorganic silicon source in the microemulsion system gradually condenses into a three-dimensional framework and at the same time the hydroxyl groups, which has obtained the organosilicon compound by hydrolysis or which it already possessed, condense with the hydroxyl groups of the framework surface and thus the organosilicon compound envelops the framework surface. Likewise, before it loses its fluidity, the microemulsion may soak the loose fiber felt base and, in combination with the fiber felt, form a composite in which both reinforce each other. The thus obtained condensate or its composite materials are further aged and solidified and after drying under normal pressure, a hydrophobic airgel and its composite materials can be obtained; simultaneously with the aging and solidification, the water in the pores of the condensate can also be replaced with the assistance of an organic solvent and subsequently a hydrophobic airgel and its composite materials can be obtained by supercritical drying.

The production method of the present invention is novel, the cost of the raw materials is low, and the range of application is wide, both a normal pressure drying process and supercritical drying can be used, and the recovered material has very good heat insulating properties and a high strength structure , and the shrinkage rate for long-term use is low.

The above embodiments are merely illustrative of the ideas of the present invention and are not limiting of the patent protection of the present invention. All non-substantial changes made to the present invention using these ideas fall within the scope of the present invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

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• CN 104003406 A [0003]

Claims (8)

A rapid production process for an airgel having a microemulsion as precursor, characterized in that it comprises the steps of: (1) preparing a microemulsion wherein a certain amount of a water-soluble silicon source is mixed with water and a certain amount of a surfactant and a cosurfactant are added ; stirring them in a blender at high speed and then slowly adding one or more organosilicon compounds as well as secondary oil phases until a semi-transparent and homogeneous microemulsion is obtained; (2) the preparation of a gel wherein accelerated gelation is performed on the microemulsion recovered in step (1) over a period of time and / or with the addition of an appropriate amount of an acidic or basic catalyst; (3) an aging and solidification process wherein aging is performed on the gel material formed in step (2) within a certain period of time and / or under heating; (4) supercritical drying or drying under atmospheric pressure, wherein the gel obtained in step (3) is subjected to supercritical drying or drying under atmospheric pressure, whereupon a hydrophobic silica airgel is obtained. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 , characterized in that the water-soluble silicon source in step (1) is water glass, an acidic silica sol with water as solvent, a basic silica sol with water as solvent, lithium methyl silicate, sodium methyl silicate, potassium methyl silicate, lithium silicate, lithium metasilicate, sodium silicate, sodium metasilicate, potassium silicate or potassium metasilicate or a Combination of several of these is; the surfactant in step (1) is sodium dioctylsulfosuccinate, sodium laurylsulfonate, sodium dodecylbenzenesulfonate, sodium laurylsulfate, fatty alcohol polyoxyethylene ether sodium sulfate, polysorbate 60, polysorbate 80, Span 20 or polyethylene glycol monooleate or a combination of any of these; the cosurfactant in step (1) is acetone, methyl butanone, methyl isobutyl ketone, ethyl acetate, methanol, ethanol, ethylene glycol, 1-propanol or 2-propanol or a combination of any of these; the organosilicon compound in step (1) is hexamethyldisiloxane, hexamethyldisilazane, dimethyldiethoxysilane, monomethyldiethoxymonohydrosilane, methyltriethoxysilane, methyltrimethoxysilane, polymethyltriethoxysilane, polymethyltrimethoxysilane, methylhydroxysilicone oil, hydroxyhydrogensilicone oil, methyltrifluoropropylsilicone oil or methylvinylsilicone oil or a combination of any of them; and the secondary oil phase in step (1) is n-hexane, cyclohexane, n-pentane or liquid paraffin or a combination of several of these. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 characterized in that the acidic catalyst in step (2) is hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, clover acid, acetic acid or ethanedioic acid or a combination of any of these; and the basic catalyst in step (2) is ammonia water, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, sodium carbonate or potassium carbonate, or a combination of any of them. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 or 3 characterized in that before adding in step (2) an acidic or basic catalyst, to the microemulsion obtained in step (1) an appropriate amount of an inorganic additive is added and after uniform mixing the microemulsion by the method of penetration by spraying or a complete dipping with a fiber material is combined, wherein the microemulsion after the conversion into a gel forms a unit with the fiber. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 4 characterized in that the fibrous material is a glass fiber, an aluminosilicate fiber, a mullite fiber, a basalt fiber, a polyester fiber, a polyacrylonitrile fiber, a carbon fiber or a viscose fiber, or a combination of any of these; and the inorganic additive is titanium dioxide, ferric oxide, ferrous oxide, alumina, magnesia, zinc oxide, aluminosilicate, magnesium silicate, calcium silicate, zinc silicate, zinc borate, magnesium hydroxide, aluminum hydroxide or ferric hydroxide or a combination of several of these. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 , characterized in that the period of time for aging in step (3) is 10 minutes to 10 hours and the aging temperature is 10 to 75 ° C. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 or 6 , characterized in that in the aging process in step (3) a certain amount of organic solvent is added, wherein the organic solvent is methanol, ethanol or acetone or a combination of several of these. Rapid manufacturing process for an airgel with a microemulsion as precursor to Claim 1 characterized in that in step (4) under normal pressure conditions the drying temperature is 50-200 ° C, under conditions of supercritical drying with carbon dioxide is 30-65 ° C; and under the conditions of supercritical drying with ethanol, the drying temperature is 220-250 ° C.

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