JP3084394B2 - Aerogel bonded to glass surface and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing aerogel bonded to a glass surface in order to improve the strength and handleability of the aerogel or to obtain an aerogel of any shape.

[0002]

2. Description of the Related Art Aerogel is a substance having a very high porosity and a large surface area, which is obtained by preparing a wet gel and supercritically drying the wet gel. It is known to exhibit unique physical properties such as properties, low density, and low refractive index. Therefore, conventionally,
With respect to the aerogel having such properties, its production method, property evaluation, applied technology, and the like have been actively studied (HD GESSSER and PCGO).
SWAMI, “Aerogels and Relat
ed Porous Materials ", Chem
cial Review, 89, 765 (1989),
Koji Tajiri "Characteristics and Applications of Aerogels", Surface Science
Vol. 14, No. 9, 28 (1993), Koji Tajiri "Characteristics and application of translucent silica airgel", Chemical Industry, Vol. 47, 288 (1996)).

[0003] With regard to the most commonly researched and prepared silica aerogels, the generally used preparation methods are as follows. As a raw material for silica,
Methyl silicate, ethyl silicate, or oligomers thereof are exclusively used because of the ease of handling of the gelation reaction and the availability such as price. Methyl silicate or its oligomer is diluted with methanol and ethyl silicate or its oligomer is diluted with ethanol at an appropriate ratio to obtain a silica wet gel having a desired silica concentration, and therefore a silica aerogel having a desired density. To cause a hydrolysis and gelation reaction to produce a silica wet gel. The liquid phase of the obtained silica wet gel is methanol when diluted with methanol, and ethanol when diluted with ethanol. After the aging treatment, the silica wet gel is placed in an autoclave, and the autoclave is filled with methanol when the liquid phase of the silica wet gel is methanol and ethanol when the liquid phase is ethanol. After slowly heating the autoclave to a temperature and pressure above the critical point of each alcohol (for example, 300 ° C., 80 atm), the alcohol is slowly released from the autoclave to zero while maintaining the temperature above the critical temperature. Allow to drain until completely removed. Thereafter, the temperature is lowered to take out the produced silica airgel (this is called supercritical drying with alcohol). Alternatively, a silica wet gel in which the liquid phase is alcohol or acetone is placed in an autoclave, and after filling the autoclave with the same alcohol or acetone as the liquid phase of the wet gel, the liquid in the autoclave is replaced with liquefied carbon dioxide. Heat to a temperature and pressure above the critical point of carbon dioxide (eg, 40 ° C., 90 atm), then slowly and completely remove the carbon dioxide while maintaining the temperature above the critical temperature and lower the temperature to produce The silica airgel thus obtained is taken out (this is called supercritical drying with carbon dioxide).

[0004] Aerogels of inorganic oxides such as zirconia, organic polymers such as phenolic resins, and organic-inorganic mixtures have also been prepared, but the preparation method is basically the same as that of silica, and the starting materials ( An aerogel can be obtained by preparing a wet gel of the target substance from the liquid mixture) by a sol-gel method (in the case of an inorganic substance) or a polymerization reaction (in the case of an organic substance) and then supercritically drying the wet gel. In the case of an organic substance, supercritical drying with carbon dioxide is exclusively used due to the heat resistance.

At present, the monolithic aerogels obtained by these production methods have only enough strength to break easily. For this reason, some reinforcement is required for applications that require strength, for example, for use in window glass as a transparent heat-insulating material, or that require strength and transparency in some cases. Conventionally, for this reinforcement, a practical method has been proposed in which, for example, a sheet glass is placed on both sides, and an aerogel is sandwiched between two sheet glasses to secure strength on the sheet glass side and maintain transparency. (KI Jensen, "Passi
ve solar component based
on evaluated monolithic s
ilica aerogel ", Journal of
Non-Crystalline Solids, V
ol. 145, 237 (1992); J. Pl
atzer, P .; O. Brown, “Transpar
ent Insulation Technology
for Buildings-a review ",
Proceedings of Window Inn
ovations '95, p. 588 (1995)). However, in the method in which the sheet glass is placed on both sides after the aerogel is produced, the operation cost is high, and the aerogel is likely to be damaged during the operation.

If an aerogel can be produced in a form bonded to glass, the process for application after the aerogel is produced can be greatly simplified, such as practical use, and the occurrence of breakage of the aerogel during the process can be greatly reduced. It is thought that it is possible. In addition, it is considered that an airgel having an arbitrary shape can be easily obtained by bonding an airgel to a glass surface having an arbitrary shape.

As described above, since aerogel is obtained by supercritical drying of a wet gel, a wet gel is formed on a glass surface, and the entire body, including the glass, is supercritically dried as it is and bonded to glass. It is also believed that airgel can be made. However, the glass as it is,
Or, if used only after washing by the usual method,
The obtained aerogel and the glass were weakly or not bonded at all, and the aerogel and the glass were easily separated, and it was difficult to produce an aerogel firmly bonded to the glass.

[0008]

SUMMARY OF THE INVENTION Under such circumstances, the present invention has been made for the purpose of reliably producing an aerogel in a form firmly bonded to glass and providing an aerogel in such a form. Things.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, a glass on which aerogel is to be formed on the surface thereof is first treated with ammonium acid fluoride (HF.NH _4). F) The glass surface is activated by immersing it in a solution having a property of corroding glass such as an aqueous solution, and after removing the solution by washing with water, the mixed solution serving as a starting material for the wet gel is poured onto the glass surface. Aqueous gel was produced by causing a gelling or polymerizing reaction to form a wet gel attached to the glass, and then drying it in an autoclave in a supercritical manner to obtain an aerogel bonded to the glass. Was. During this operation, it is necessary to dry the activated glass surface and pour the starting material mixture of the wet gel without exposing it to air.

The present inventors have obtained the above findings and completed the present invention. That is, the present invention relates to a method of immersing glass in a solution that erodes the glass surface, such as an aqueous solution of hydrofluoric acid or an aqueous solution of ammonium ammonium fluoride. A glass characterized by pouring a reaction solution that is a body, causing a gelling or polymerization reaction on the glass surface to produce a wet gel attached to the glass, and then supercritically drying the generated wet gel. An object of the present invention is to provide a method for producing an airgel bonded to a surface. Further, the present invention, the solution eroding the glass surface, hydrofluoric acid aqueous solution, acidic ammonium fluoride aqueous solution, acidic ammonium fluoride aqueous solution, potassium hydrogen fluoride, aqueous solution of hydrogen fluoride such as sodium hydrogen fluoride, or The method for producing the aerogel, which is one kind selected from organic solvent solutions such as alcohol solutions thereof, and a reaction solution serving as an aerogel precursor is obtained by reacting with a silicate alkoxide such as methyl silicate or ethyl silicate or an oligomer thereof. Water, and an alcohol such as methanol or ethanol, if necessary, a mixed solution to which an alkali such as ammonia or an acid such as acetic acid is added as a catalyst, titanium isopropoxide, zirconium n-propoxide, and metal alkoxide such as aluminum ethoxide. Water and alcohol, if necessary, acetylacetone A mixture of various condensation inhibitors, a plurality of metal alkoxides such as silicate alkoxides and aluminum alkoxides, water and an alcohol, and if necessary, a mixture of catalysts, aqueous solutions of phenols such as resorcinol and phenol and aqueous solutions of formaldehyde, and 1 is selected from a mixed solution containing a catalyst such as sodium carbonate and a solution obtained by mixing a melamine aqueous solution and a formaldehyde aqueous solution.
The above-described method for producing aerogel, which is a seed, is a desirable embodiment. Further, the present invention provides an airgel bonded to a glass surface produced by the above-mentioned production method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The glass used in the present invention is a solution that erodes and activates the glass surface. As the solution, an aqueous solution of ammonium ammonium fluoride or an aqueous solution of hydrofluoric acid is preferable. can give. Other examples include aqueous solutions of hydrogen fluoride such as potassium hydrogen fluoride and sodium hydrogen fluoride, and respective alcohol solutions. The solution which erodes the glass surface is usually considered to be a 5% by weight aqueous solution of ammonium acid fluoride, considering the safety of handling and the appropriate reaction rate with the glass. If you do
It is not limited to the solution described above.

Next, the glass is immersed in the above solution.
When using glass that is not so dirty such as glass delivered as new, it may be immersed in the solution as it is. If the surface of the glass is dirty such as oil stains such as fingerprints or mud stains, wash the glass with an appropriate method such as acetone washing, water washing, or washing with a detergent, and then immerse the glass in the solution. The glass surface may not be eroded cleanly and not activated due to uneven wettability.

The time for immersing the glass in the above solution is, for example, about 2 to 5 minutes when a 5% by weight aqueous solution of acidic ammonium fluoride is used at room temperature. The smoothness and transparency of the glass surface may be impaired. Of course, this time should be appropriately selected according to the concentration and type of the solution.

The glass taken out of the solution is immediately washed with a clean liquid such as distilled water to remove erosive chemicals.
Thereafter, the glass surface may never be dried and exposed to air, e.g., the glass may be stored in a clean liquid until the wet gel starting material mixture of the aerogel precursor reaction is poured onto the glass surface. Need not be. When the glass is exposed to air, the effect of erosion and activation of the glass surface by the solution is lost. It is not preferable to store the glass in a clean liquid for an excessively long period of time. If possible, it is preferable to pour a wet gel starting material mixture of a reaction liquid to be an airgel precursor immediately after the cleaning treatment. As a reaction solution serving as an airgel precursor, that is, a mixed solution of a wet gel starting material, for example, in the case of silica, preferably, methyl silicate, ethyl silicate, or methanol, ethanol or the like is used with respect to 1 mol of an oligomer thereof. 2 to 40 moles of alcohol, 2 to 10 moles of water, and, if necessary, a mixed solution to which a catalyst such as ammonia or acetic acid is added. Particularly preferably, 5 to 20 moles of alcohol to 1 mole of silicate alkoxide, Water 4-8
A mole is used as a catalyst, and ammonia is added to water, and a mixed liquid is used in which 4 to 8 moles of water to be added is replaced with 0.05 to 0.1 normal ammonia water.
Further, a mixed solution containing a metal alkoxide such as zirconium n-propoxide, titanium isopropoxide, aluminum ethoxide and an alcohol, water, and, if necessary, a reaction inhibitor such as acetylacetone, may be used, for example, zirconia, titania, alumina, etc. Exemplified as a wet gel starting material mixture. Further, a mixed aqueous solution of a phenol such as resorcinol and phenol, or a catalyst such as melamine and formaldehyde and, if necessary, sodium carbonate is exemplified as a wet gel starting material mixed solution of a phenol resin or a melamine resin. Further, a mixture of a silicate alkoxide and an aluminum alkoxide, an alcohol, water, a catalyst and the like are exemplified as a wet gel starting material mixture of an inorganic-inorganic mixture such as cordierite (silica-alumina mixed composition). You. Gelation or polymerization of the reaction solution is performed in air or in a closed container,
Room temperature or constant temperature up to 90 ° C (for organic polymer)
It is carried out by leaving it still for several minutes to several days.

[0015] After the wet gel is formed on the glass by gelation or polymerization, it is immersed in alcohol or the like to replace the liquid phase of the wet gel and aging in the same manner as in the usual aerogel preparation method. Do
Supercritical drying is performed in an autoclave to obtain an airgel bonded to glass. Specifically, for example, immersion in methanol, ethanol, isopropyl alcohol, or the like, replacement and aging of the wet gel liquid phase are performed. The wet gel attached to the glass is placed in an autoclave, and the autoclave is filled with a wet gel liquid phase liquid such as methanol. It takes more than 1 to 10 hours depending on the size of the wet gel, and the critical point of the liquid phase of the wet gel (for example, 63 atm for ethanol, 243 ° C) or more (for example, 80 atm, 300 ° C) The temperature is increased and the pressure is increased until the liquid phase becomes a supercritical fluid. Thereafter, the supercritical fluid is discharged and removed to atmospheric pressure over 30 minutes to several hours. Thereafter, the temperature is lowered to room temperature over about half a day, and the airgel bonded to the produced glass is taken out (supercritical drying with alcohol).
Alternatively, the wet gel liquid phase is replaced with ethanol or acetone by immersion in ethanol or acetone, and aging is also performed. The airgel attached to the glass is placed in an autoclave, and the autoclave is filled with ethanol or acetone. The liquefied carbon dioxide is fed while maintaining the condition that the liquefied carbon dioxide does not evaporate, for example, 25 ° C. or less, 80 atm or more, and completely replaces the liquid phase in the autoclave with the liquefied carbon dioxide over several hours to two days. I do. Then, the critical point of carbon dioxide (73 atm, 3
(1 ° C.) or more (e.g., 90 atm, 60 ° C.) over several tens of minutes to several hours to raise the temperature and pressure to make the liquid phase a supercritical fluid. Thereafter, carbon dioxide is discharged and removed to atmospheric pressure over 30 minutes to several hours. Thereafter, the heating is stopped, and when the temperature drops to around room temperature, the airgel bonded to the produced glass is taken out (supercritical drying with carbon dioxide).

The above-mentioned glass is not limited to a sheet glass, and for example, an aerogel bonded to glasses of various shapes can be obtained by using, for example, a curved glass, a glass tube, or the like having an appropriate shape. it can.

[0017]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 A dish made of hard glass was washed by the following various methods. (1) Those that have been washed only with water. (2) After rubbing with a sponge to which a neutral detergent has been applied, and then washing with water. (3) Ultrasonic cleaning in the order of a neutral detergent aqueous solution, distilled water, ethanol and acetone for 15 minutes each. (4) After washing in the above (3), immersed in diluted hydrochloric acid for 1 day, washed with distilled water to remove the diluted hydrochloric acid, and immediately used in the operation described below without drying. (5) After washing with a neutral detergent, soaked in a 5% by weight aqueous solution of ammonium ammonium fluoride for 3 minutes, washed with distilled water, dried and stored. (6) Similar to (5) above, immersed in a 5% by weight aqueous solution of ammonium ammonium fluoride for 3 minutes, washed with distilled water, and immediately used for the operation described below without drying.

A solution prepared by mixing 1 mol of methyl silicate, 10 mol of methanol, and 6 mol of 0.1 N aqueous ammonia in water was poured into these petri dishes. About 3
At 0 minutes, the solution gelled, producing a wet gel of silica in the Petri dish.

After wrapping in a wrap to prevent drying from the surface of the wet gel and leaving it to stand for one day, the gelling reaction is further advanced.
The wet gel is immersed in a large amount of petroleum in a large amount of ethanol, and the operation of replacing the ethanol once every half day is repeated for two days.
The liquid phase of the wet gel was completely replaced with ethanol. After that, put the wet gel together with the petri dish in the autoclave,
After filling the autoclave with ethanol,
A silica airgel was obtained by performing a supercritical drying operation using ethanol as a supercritical medium at an atmospheric pressure and 260 ° C.

Table 1 shows the degree of bonding of the obtained silica airgel to a glass petri dish. The state of bonding was evaluated by visual observation and whether the glass plate and the airgel were separated or the aerogel itself was damaged when a shear stress was applied by hand between the aerogel and the glass plate.

[0022]

[Table 1]

When the glass and silica airgel were used after being immersed in an aqueous ammonium solution, washed with distilled water and not dried, the glass and the silica airgel were firmly bonded, and the bonding state between the two was extremely good.

Example 2 An aqueous solution prepared by mixing 2 mol of formaldehyde, 0.005 mol of sodium carbonate and 85 mol of water with respect to 1 mol of resorcinol was added to a 5% by weight aqueous solution of ammonium ammonium fluoride for 5 minutes and then distilled. Place in a glass Petri dish that has been washed with water and the surface has not been exposed to the air as it is, or washed with a neutral detergent and then washed with water, placed in a closed container, and placed in a thermostat at 95 ° C for 4 days. ,
Polymerized. The wet gel in the form adhered to the obtained glass is first immersed in a liquid of water 2: acetone 1 (weight ratio) and left for half a day, and then acetone: water 1: acetone 2, water 1: acetone 9 and gradually acetone After immersing the mixture in a highly concentrated mixture for half a day, the operation of replacing the liquid phase of the wet gel with acetone is repeated, and finally, the operation of immersing in 100% acetone and leaving for half a day is repeated twice to obtain a wet gel. The liquid phase was completely replaced with acetone. Next, the polymer wet gel attached to the glass was put into an autoclave, and the inside of the autoclave was filled with acetone.
While maintaining the pressure of 80 atm or more, the liquefied carbon dioxide is fed into the autoclave at a rate of 10 to 20 ml / min for 2 hours by a liquid sending pump, and the operation of replacing with acetone is repeated once a half day three times, and the liquid phase is separated. It was replaced by liquefied carbon dioxide. Then, take about 1 hour,
The temperature was raised and raised to 0 atm and 60 ° C., and then carbon dioxide was discharged over about 2 hours. After the discharge was completed, the heating was stopped, and when the temperature dropped to around room temperature, the airgel was taken out.
Among the obtained phenolic (resorcinol-formaldehyde) resin aerogels, those using a glass petri dish treated with acidic ammonium fluoride were bonded to glass, while those washed with a neutral detergent were separated.

[0025]

According to the present invention, aerogels bonded to glass can be reliably obtained, and aerogels of various shapes can be produced according to the shape of glass. The airgel in the state of being bonded to the glass according to the present invention is kept strong by the glass, and in the case of a highly transparent airgel such as silica aerogel, its transparency is maintained even in the state of being bonded to the glass. It is expected to greatly contribute to the reduction of the cost of introducing aerogels, as it will be easier to handle when applied to window materials etc. as a transparent heat insulating material, and the processing process for window materials can be greatly simplified. Is done.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yutaka Tai 2-3-3 Yoshioka-cho, Owariasahi-city, Aichi Prefecture 27 (56) References JP-A-10-45429 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) C03C 15/00-23/00

Claims (4)

(57) [Claims] 1. A method of immersing a glass in a solution that erodes the glass surface, such as an aqueous solution of hydrofluoric acid or an aqueous solution of ammonium ammonium fluoride, and washing the glass surface without exposing the glass surface to air. After pouring a reaction solution that will cause a gelling or polymerization reaction on the glass surface to produce a wet gel attached to the glass, the resulting wet gel is supercritically dried. Of producing aerogels bonded to a surface. 2. A solution for eroding the glass surface is selected from an aqueous solution of hydrofluoric acid, an aqueous solution of acidic ammonium fluoride, an aqueous solution of hydrogen fluoride such as sodium hydrogen fluoride and potassium hydrogen fluoride, or an alcohol solution thereof. The method for producing an airgel according to claim 1, which is one kind of the airgel to be produced. 3. A reaction solution serving as an airgel precursor is a mixed solution containing silicate alkoxide or an oligomer thereof, water and an alcohol, and if necessary, an alkali or an acid as a catalyst, titanium isopropoxide or zirconium n-propoxy. , A mixture of a metal alkoxide such as aluminum ethoxide and water, and an alcohol, if necessary, a condensation inhibitor such as acetylacetone, a plurality of metal alkoxides such as silicate alkoxide and aluminum alkoxide, water and an alcohol, if necessary , A mixture of catalysts, an aqueous solution of phenols such as resorcinol or phenol and an aqueous solution of formaldehyde, and, if necessary, a mixed solution containing a catalyst such as sodium carbonate, or a mixture of an aqueous solution of melamine and an aqueous formaldehyde solution. Claim that is Item 4. A method for producing the airgel according to Item 1. 4. An airgel bonded to a glass surface produced by the production method according to claim 1.