METHOD FOR PRODUCING A HYDROPHILIC AEROGEL GRANULE AND APPLICATION OF THE PRODUCT THEREOF

Abstract

A method for producing a hydrophilic aerogel granule is provided, which includes the steps of: mixing for the siloxane solvent mixture preparation, hydrolysis with proper acid catalyst, condensation dispersion by introducing a proper alkali catalyst into the mixture and dispersing it with hydrophobic dispersion solvent to obtain wet gel, aging under a specific temperature, disintegration dispersion for disintegrating the wet gel and dispersing it in the dispersion solvent, high temperature solvent exchange under ambient temperature with dispersion solvent, and solvent evaporation for removing the dispersion solvent.

Claims

1. A method for producing a hydrophilic aerogel, comprising: mixing step, wherein a reaction solution is prepared by mixing an alkoxysilane with a proper solvent; hydrolysis step, wherein an acid catalyst is added into the reaction solution for hydrolysis reaction; condensation dispersion step, wherein an alkali catalyst is added into the reaction solution to initiate condensation reaction, and during the condensation reaction, a hydrophobic disperse solvent is added and the reaction solution is rapidly stirred to form a uniform wet get structure of aerogel; aging step, wherein the aerogel structure is stabilized under a specific temperature; disintegration dispersion step, wherein the aged aerogel is dispersed in a large amount of a hydrophobic dispersion solvent, and then the bulk of gel is broken into particles with a diameter ranging from several centimeters to dozens of centimeters; solvent exchange step, wherein ambient pressure and high temperature are introduced to make the aerogel completely transparent or transparent with a tint of blue light; and solvent evaporation step, wherein the hydrophobic dispersion solvent is removed by high temperature distillation or filtered by a proper kind of filter, and then the aerogel is dried to obtain a hydrophilic aerogel with high porosity and high specific surface area.

2. The method as claimed in claim 1, wherein the alkoxysilane is an alkoxysilane compound or a R-alkoxysilane compound; the alkoxysilane compound is tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), or tetramethyl orthosilicate; the R-alkoxysilane compound is R-tetramethyl orthosilicate or R-tetraethyl orthosilicate, the R represents a hydrophilic functional group including a carboxyl group COOH, an amino group NH.sub.2, an imino group NH, a hydroxyl groups OH, an amide group CONH, an epoxy group CH(O)CH, an urea group NHCONH, a cyanate group NCO, or an isocyanate group NCON, and a carbon number of the R is of 1 to 8.

3. The method as claimed in claim 1, wherein the proper solvent contains water, treated water, distilled water or ethanols.

4. The method as claimed in claim 1, wherein the hydrophobic disperse solvent is alcohol, aromatic, or alkane; the alcohol is methanol or ethanol; the aromatic is benzene, toluene, or xylene; the alkane is n-hexane, n-pentane, or cyclohexane.

5. The method as claimed in claim 1, wherein the hydrophobic dispersion solvent is aromatic or alkane; the aromatic is benzene, toluene, or xylene; the alkane is n-hexane, n-pentane or cyclohexane.

6. The method as claimed in claim 1, wherein the solvent exchange step is performed under 50 C. to 160 C. and ambient pressure.

7. The method as claimed in claim 1, wherein the distillation in the solvent evaporation step is performed under atmospheric pressure and 70 C. to 150 C.; the drying in the solvent evaporation step is performed under 90 C. to 150 C. using a fluid bed dryer, an oven, a drum dryer, a mixer dryer, a spray dryer, or a vacuum drying equipment.

8. The method as claimed in claim 1, wherein density, particle size, porosity, and pore size of the hydrophilic aerogel is subject to the following factors used in the method: alkoxysilane content, R-alkoxysilane content, the amount of solvents, solvent viscosity, acid catalyst concentration, alkali catalyst concentration, hydrophobic disperse solvent species and content, hydrophobic dispersion solvent species and content, the temperature for the solvent exchange step, or stirring rate.

9. The method as claimed in claim 1, wherein the hydrophilic aerogel is used for being added to a hydrophilic substrate, a hydrophilic glue, or a hydrophilic organic material to enhance heat proof and fire resistance of the hydrophilic substrate, the hydrophilic gel, or the hydrophilic organic material; the hydrophilic substrate is cement, cement paint and clay; the hydrophilic glue is hydrophilic PU glue, hydrophilic PMMA glue, or silicone.

10. The method as claimed in claim 9, wherein the hydrophilic aerogel is used for being added to cement to form concrete, and the concrete is used for a spray coating of RC structure or H-beam, a plaster of an RC structured wall or a brick wall, or a base of an RC structured wall or a brick wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1: the flow chart of hydrophilic aerogel manufacturing process diagram of this invention.

[0028] FIG. 2: the appearance of the hydrophilic aerogel prepared with this invention.

[0029] FIG. 3: the SEM image of the aerogel prepared with this invention.

[0030] FIG. 4: the appearance and weight of the concrete made with the hydrophilic aerogel and commercial cement-sand. (the ratio of aerogel to cement-sand is of 2 to 1).

[0031] FIG. 5: the cross-section image of the concrete made with the hydrophilic aerogel and commercial cement.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The detailed description and preferred embodiments of the invention will be set forth in the following content, and provided for people skilled in the art so as to understand the characteristics of the invention.

[0033] FIG. 1 discloses the hydrophilic aerogel manufacturing process, which includes the following steps of: mixing (S1), hydrolysis (S2), condensation dispersion (S3), aging (S4), disintegration dispersion (S5), high temperature solvent exchange (S6), and solvent evaporation (S7).

[0034] Mixing (S1): The reaction solution is prepared by mixing alkoxysilane, R-alkoxysilane or their mixtures with proper solvents. The alkoxysilane can be tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) or tetramethyl orthosilicate. The R-alkoxysilane can be R-tetramethyl orthosilicate or R-tetraethyl orthosilicate, where R represents hydrophilic functional groups, which includes COOH, NH.sub.2, NH, OH, CONH, CH(O)CH, NHCONH, NCO, or NCON. The number of carbon atom is ranged from 1 to 8. The purpose of the addition of R-alkoxysilane is to modify the micro-structure of aerogel and control the content of functional groups. The total content of alkoxysilane and R-alkoxysilane is ranged from 3.0 to 60.0 mol % and the amount of solvent is range between 97.0 to 40.0 mol %.

[0035] The solvents used in the mixing process can be water, distilled water, deionized water, secondary distilled water, alcohol with 1 to 10 carbons, ether with 2 to 10 carbons, or ketone with 3 to 10 carbons. More specifically, those organic solvents can be ethanol, acetone, ethoxyethane, or dibutyl ether.

[0036] Hydrolysis (S2): An acid catalyst is added to the solution obtained in the mixing step (S1) to initiate the hydrolysis reaction. The ratio of alkoxysilane and R-alkoxysilane to acid catalyst is ranged from 1:0.5 to 1:0.001; In addition, some of these R-alkoxysilane do not require catalysts to proceed the hydrolysis reaction.

[0037] The hydrolysis reaction time was about 360 minutes when the ratio of the total content of alkoxysilane with R-alkoxysilane to the catalyst equals to 1:0.001; while it only takes about 10 min as the ratio of the total content of alkoxysilane with R-alkoxysilane to the catalyst was increased to 1:0.5. Accordingly, the processing time of hydrolysis was related to the concentration of the catalyst.

[0038] Condensation dispersion (S3): Alkali catalyst was added to the reaction solution. The molar ratio of acid catalyst to alkali catalyst was between 1:1 to 1:3.

[0039] The experimental results had shown that the condensation time (i.e. the gelation time) decreased as the concentration of alkali-catalyst increased. When the molar ratio of acid catalysts to alkali catalysts equaled to 1:1, the gelation time was about 1,600 minutes; when the molar ratio changed to 1:3, the gelation time would become 1 minute only. Hence, the entire processing time could be controlled by the content of alkali catalyst.

[0040] The reaction solution had become a sol-like solution at the end of the condensation dispersion step. A significant amount of hydrophobic dispersion solvent was then added into the sol-like solution followed by rapid stirring (stirring speed was set between 100 to 500 rpm). During this process, the strong interaction between water molecules and silica structure was suppressed by the interference of solvent molecules from the dispersion solvents. Finally, the sol was converted into hydrophilic wet gel. The volume ratio of the reaction solution and dispersion solvent was set from 1:0.0 to 1:0.3. As the content of the hydrophobic dispersion solution became higher, the gel's porosity went higher and the density became lower. However, the appearance of the gel became less transparent as the degree of phase separation intensified.

[0041] The solvents used in condensation dispersion (S3) could be alcohols with 2 to 10 carbon atoms, aromatics with 6 to 10 carbon atoms, alkanes with 5 to 10 carbon atoms, aromatic alcohols with 2 to 6 carbon atoms, aromatic halide with 6 to 12 carbon atoms, or alkyl halide with 6 to 12 carbon atoms. More specific, the solvents can be methanol, ethanol, cyclohexane, n-hexane, benzene, or toluene.

[0042] Aging (S4): The structure of the hydrophilic aerogel is stabilized by the heat treatment in a specific range of temperature. More specific, the aging temperature can be of 20-80 C. For example, the aging temperature is of 40-50 C.

[0043] Disintegration dispersion (S5): The hydrophilic wet gel was dispersed and disintegrated in the hydrophobic solvents, and was broken into particles with the diameters ranged from hundreds of micrometers to dozens of millimeters.

[0044] The hydrophobic solvents use in disintegration dispersion (S5) can be aromatics with 6 to 10 carbon atoms, alkanes with 5 to 10 carbon atoms, or their mixtures. To be more specifically, the solvents can be cyclohexane, n-hexane, benzene, or toluene.

[0045] High temperature solvent exchange (S6): This step was prepared under ambient pressure and high temperature. The high temperature solvent exchange process used both hydrophilic and hydrophobic solvents. Utilizing the co-boiling effect of water, ethanol and hydrophobic solvents, water molecules that trapped inside the micropore of wet gel were replaced and the wet get became totally transparent or slightly with blue tone. Thereafter, the hydrophilic aerogel product with low density and high porosity was manufactured. More specific, the solvent exchange temperature can be of 50-160 C.

[0046] Solvent evaporation (S7): Hydrophilic aerogels with low density were obtained by the rapid heating process from 70 C. to 150 C. under atmospheric pressure after filtering out the residual solvents or after high temperature distillation. Furthermore, the solvent evaporation process was preceded from 70 C. to 150 C. by the high temperature flow bed or oven and the dried hydrophilic aerogel granule were obtained. More specific, the high temperature distillation is performed under 90 C. to 150 C. and atmospheric pressure.

[0047] According to this process, hydrophilic aerogel granule with the diameter size ranged from hundreds of micrometers to dozens of millimeters were prepared. In addition, surface modification was made available by using this invention. With different kinds of surface modifier, the aerogel could be applied to different kind of hydrophilic cements, paints and adhesives with proper organic solvents, and thereby the application areas of the aerogel are expanded. Especially in the preparation of fireproof concrete area, hydrophilic aerogels can be used to improve the degree of fire proof and heat resistance significantly.

[0048] The appearance and SEM image of the hydrophilic aerogel granule are shown in FIGS. 2-3. The results indicated that the size of the aerogel granule was between several millimeters to dozens of millimeters in diameters.

[0049] FIG. 4 displays the appearance and weight of the concrete segments prepared with cement and hydrophilic aerogels (1:2 volume ratio). The weight of the samples prepared from commercial cement and cement-aerogel are of 1420.5 g and 788.2 g, respectively. The concrete segment weight prepared with this invention is only 55% of the commercial cement sample under the same volume. Therefore, the hydrophilic aerogel granule prepared by this method can be applied to the light weight architectural design areas.

[0050] FIG. 5 presents the cross-section image of the concrete sample described above. Aerogel Granules dispersed homogeneously in the cement. In other words, this composite material did not exhibit a macroscopic phase separation.

[0051] Concrete samples prepared by this method as described above were examined by the surface temperature under the high temperature environment. The thickness of concrete specimen was of 3 cm. Concrete specimens were placed on the heating plate at 70 C. for 6 hours under the room temperature environment. The measured surface temperature of concrete specimen without aerogel was of about 47.4 C., while the surface temperature of concrete specimen with aerogel granule prepared by this method was only of 32 C. The tested results indicate the superior heatproof character of the product using aerogel granule prepared by this method.

[0052] A comparison experiment with the extremely high temperature torch at 1200 C. heating at one side of the surface for 1 hour was carried out for above samples. The resulted surface temperature at the opposite side of concrete specimen were of 321.1 C. and of 74.7 C. for specimen without aerogel granule and with the aerogel granule respectively. This experiment demonstrated the outstanding character of fire resistance products of aerogel granule prepared by this method.

[0053] While the invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.