Method for continuously manufacturing an aerogel powder having a hydrophobic-hydrophilic bipolar core-shell structure

Abstract

A method for producing an aerogel granule having a hydrophobic-hydrophilic bipolar core-shell structure combines an aerogel precursor having a hydrophilic structure with another aerogel precursor having a hydrophobic structure. The method comprises the steps of: mixing a hydrophilic alkoxysilane compound, a hydrophobic alkyl-substituted alkoxysilane compound, and an organic solvent to form a mixture; adding an acidic catalyst to the mixture to perform hydrolysis; adding a basic catalyst to the hydrolyzed mixture to perform condensation, and during the condensation adding a dispersion solvent to the hydrolyzed mixture and stirring the hydrolyzed mixture to gelate so as to form the aerogel granule having a hydrophobic-hydrophilic bipolar core-shell structure.

Claims

1. A method for manufacturing an aerogel powder, comprising: mixing a hydrophilic alkoxysilane compound, a hydrophobic alkyl-substituted alkoxysilane compound, and an organic solvent to form a mixture; adding an acidic catalyst to the mixture to perform hydrolysis; adding a basic catalyst to the hydrolyzed mixture to perform condensation, and during the condensation adding a dispersion solvent to the hydrolyzed mixture and stirring the hydrolyzed mixture for gelation so as to form an aerogel granule; and heating the aerogel granule in a fluidized bed or an oven under a temperature of 80-250 C. to form an aerogel powder; wherein provided that the dispersion solvent is a hydrophobic dispersion solvent, the aerogel granule is an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core and the aerogel powder is an aerogel powder having a hydrophobic outer shell and a hydrophilic inner core; before completion of the condensation, the hydrolyzed mixture becomes a viscous sol, the hydrophobic dispersion solvent is added to the hydrolyzed mixture, and then the hydrolyzed mixture is stirred so that the hydrolyzed mixture gelates under dispersion force caused by the hydrophobic dispersion solvent to form the aerogel granule having a hydrophobic outer shell and a hydrophilic inner core; or wherein provided that the dispersion solvent is a hydrophilic dispersion solvent, the aerogel granule is an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core and the aerogel powder is an aerogel powder having a hydrophilic outer shell and a hydrophobic inner core; before completion of the condensation, the hydrolyzed mixture becomes a viscous sol, the hydrophilic dispersion solvent is added to the hydrolyzed mixture, and then the hydrolyzed mixture is stirred so that the hydrolyzed mixture gelates under dispersion force caused by the hydrophilic dispersion solvent to form the aerogel granule is an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core.

2. The manufacturing method as claimed in claim 1, wherein the hydrophilic alkoxysilane compound is tetramethoxysilane, tetraethoxysilane, R group-trimethoxysilane, or R group-triethoxysilane; each R group is a hydrophilic group comprising a carboxyl group, an amino group, an imino group, a hydroxyl group, an amido group, an epoxy group, or an uricyl group and has 1-8 carbon atom(s).

3. The manufacturing method as claimed in claim 1, wherein the hydrophobic alkyl-substituted alkoxysilane compound is methyltrimethoxysilane, R group-trimethoxysilane, R group-tetraethoxysilane, or R group-silicone; each R group is a hydrophobic group comprising an alky group, an alkenyl group, an ester group, an ether group, an aromatic group, or a halogen and has 1-13 carbon atom(s).

4. The manufacturing method as claimed in claim 1, wherein the hydrophilic dispersion solvent is water, alcohol, amine, acid, ketone, or ether.

5. The manufacturing method as claimed in claim 1, wherein the hydrophobic dispersion solvent is ketone, ether, ester, aromatic hydrocarbon, or alkane.

6. The manufacturing method as claimed in claim 1, wherein based on total moles of the mixture, total content of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound is of 1 mol %-60 mol %, and content of the organic solvent is of 40 mol %-99 mol %.

7. The manufacturing method as claimed in claim 1, wherein an entity of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound and the acidic catalyst are at a mole ratio of 1:0.5-1:0.00001.

8. The manufacturing method as claimed in claim 1, wherein the basic catalyst and the acidic catalyst are at a mole ratio of 1:1-5:1.

9. The manufacturing method as claimed in claim 1, wherein the hydrophilic alkoxysilane compound is tetramethoxysilane or tetraethoxysilane, and the hydrophobic alkyl-substituted alkoxysilane compound is methyltrimethoxysilane.

10. The manufacturing method as claimed in claim 1, wherein an entity of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound and the acidic catalyst are at a mole ratio of 1:0.5-1:0.00001, and the basic catalyst and the acidic catalyst are at a mole ratio of 1:1-5:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart illustrating an embodiment of the present invention;

(2) FIG. 2A is a top view showing the dispersion of (i) an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core of the present invention, (ii) a single hydrophilic aerogel granule, and (iii) a single hydrophobic aerogel granule in water;

(3) FIG. 2B is a side view showing the dispersion in water of FIG. 2A;

(4) FIG. 3A is a top view showing the dispersion of (i) an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core of the present invention, (ii) a single hydrophilic aerogel granule, and (iii) a single hydrophobic aerogel granule in toluene;

(5) FIG. 3B is a side view showing the dispersion in water of FIG. 3A;

(6) FIG. 4 is a microscopic picture showing an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core and made at a stirring rate of 500 rpm has a granule size of 10 m; and

(7) FIG. 5 is a microscopic picture showing an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core and made at a stirring rate of 500 rpm has a granule size of 10 m.

DETAILED DESCRIPTION OF THE INVENTION

(8) 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.

(9) The present invention provides a technique related to continuously manufacturing an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core or an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core, and the technical effect is clearly presented in the following content.

(10) As shown in FIG. 1, an embodiment of the present invention discloses a method for producing an aerogel granule, and the method includes the steps of: a mixing step (S1), a hydrolysis step (S2), a condensation-dispersion step (S3), and a post-treating step (S4).

(11) In the mixing step (S1), a hydrophilic alkoxysilane compound and a hydrophobic alkyl-substituted alkoxysilane compound are added to an organic solvent to form a mixture. In an example, the hydrophilic alkoxysilane compound is tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), R group-trimethoxysilane (R-TMS), or R group-triethoxysilane (R-TES), and each R group is a hydrophilic group comprising a carboxyl group (COOH), an amino group (NH.sub.2), an imino group (NH), a hydroxyl group (OH), an amido group (CONH), an epoxy group (COHCOH), or an uricyl group (NHCONH) and has 1-8 carbon atom(s); the hydrophobic alkyl-substituted alkoxysilane compound is R group-trimethoxysilane (R-TMS), R group-tetraethoxysilane (R-TES), or R group-silicone, each R group is a hydrophobic group comprising an alky group (CH.sub.3), an alkenyl group (CH.sub.2CH.sub.2), an ester group (COOR), an ether group (COC), an aromatic group (C.sub.6H.sub.4), a halogen (X), or a halogen aromatic group (C.sub.6H.sub.5X) and has 1-13 carbon atom(s). An exemplary example of the R group-silicone is polydimethylsiloxane (PDMS). Based on the total moles of the mixture, the total content of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound is of 1 mol %-60 mol % and the content of the organic solvent is of 40 mol %-99 mol %.

(12) In the hydrolysis step (S2), an acidic catalyst is added to the mixture to perform hydrolysis. The entity of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound and the acidic catalyst are at a mole ratio of 1:0.5-1:0.00001. While the entity of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound and the acidic catalyst are at a mole ratio of 1:0.00001, the hydrolysis reaction takes 900 minutes; while the entity of the hydrophilic alkoxysilane compound and the hydrophobic alkyl-substituted alkoxysilane compound and the acidic catalyst are at a mole ratio of 1:0.5, the hydrolysis reaction takes 60 minutes. In conclusion, the more content the acidic catalyst has, the less time the hydrolysis reaction takes.

(13) In the condensation-dispersion step (S3), a basic catalyst is added to the mixture to perform condensation. In an example, the basic catalyst and the acidic catalyst are at a mole ratio of 1:1-5:1. Further, the increasing of the content of the basic catalyst can shorten the condensation time. While the basic catalyst and the acidic catalyst are at a mole ratio of 1:1, the condensation reaction takes 900 minutes; while the basic catalyst and the acidic catalyst are at a mole ratio of 5:1, the condensation reaction takes 1 minute. That is, the content ratio of the basic catalyst and the acidic catalyst can be adjusted to control the time for the process. In another aspect, while the condensation reaction nears completion, the mixture becomes a viscous sol.

(14) During the condensation reaction, when the mixture becomes a pre-gel, a large number of the hydrophilic dispersion solvent or the hydrophobic dispersion solvent is added thereto and stirred. By such a manner, the pre-gel becomes spherical or pearly under the dispersion force resulted from stirring. Under the environment of a large number of the hydrophilic dispersion solvent, the solvent attracts the hydrophilic alkoxysilane compound and repels the hydrophobic alkyl-substituted alkoxysilane compound so that the hydrophilic alkoxysilane compound spread outwardly to form an outer shell and the hydrophobic alkyl-substituted alkoxysilane compound gathers inwardly to form an inner core. As such, under the stirring of the hydrophilic dispersion solvent, the mixture is condensed to form an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core. Conversely, under the stirring of the hydrophobic dispersion solvent, the mixture is condensed to form an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core. The aerogel granule has a particle size of at most several hundred m or at least 100 nm, and the particle size and the stirring rate are in inverse proportion so that the particle size can be adjusted by controlling the stirring rate.

(15) An example of the hydrophilic dispersion solvent is water, conditioning water, deionized water, C1-C16 alcohol, C2-C16 ether, C3-C16 ketone, C2-C16 ester, C1-C16 acid, or C1-C16 amine. Specifically, the hydrophilic dispersion solvent is water, conditioning water, deionized water, methanol, ethanol, acetone, butyl ether, ethyl acetate, butyl acetate, formic acid, or ammonium hydroxide.

(16) An example of the hydrophobic dispersion solvent is C2-C16 ether, C3-C16 ketone, C2-C16 ester, C6-C16 aromatic hydrocarbon, C5-C16 alkane, C2-C16 halogen ether, C2-C16 halogen aromatic hydrocarbon, C2-C16 halogen alkane, or C2-C16 halogen ester. Specifically, the hydrophobic dispersion solvent is acetone, butyl ether, ethyl acetate, butyl acetate, cyclohexane, n-hexane, toluene, kerosene, or cleaning naphtha.

(17) It is noted that when using the hydrophilic dispersion solvent in the condensation-dispersion step (S3), a hydrophilic group (e.g. OH, COOH, or NH.sub.2) in the mixture is present on an outer surface of the aerogel granule and a hydrophobic group in the mixture is present in an inner core of the aerogel granule to obtain an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core.

(18) It is also noted that when using the hydrophobic dispersion solvent in the condensation-dispersion step (S3), a hydrophobic group (e.g. CH.sub.3, X, or C.sub.2H.sub.5) in the mixture is present on an outer surface of the aerogel granule and a hydrophilic group in the mixture is present in an inner core of the aerogel granule to obtain an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core.

(19) In the post-treating step (S4), the dispersion solvent in the aerogel granule is removed through filtering the aerogel granule with a filter. After which, an aerogel powder having a hydrophilic outer shell and a hydrophobic inner core or an aerogel powder having a hydrophobic outer shell and a hydrophilic inner core is obtained.

(20) In order to rapidly obtaining the aerogel powder, the aerogel granule is alternatively heated in a fluidized bed or an oven under a temperature of 80-250 C.

(21) According to the method described above, a surface-hydrophilic homogenous spherical aerogel granule or a surface-hydrophobic homogenous spherical aerogel granule is manufactured. In another aspect, the homogeneity in appearance and size of the aerogel granule is enhanced to increase its application. In the other aspect, the method can directly provide a surface-hydrophilic aerogel granule or a surface-hydrophobic aerogel granule so it is suitable for mass production.

(22) As shown in FIGS. 2A and 2B, an aerogel granule having a hydrophilic outer shell and a hydrophobic inner core, a single hydrophilic aerogel granule, and a single hydrophobic aerogel granule are added to water. Since the single hydrophobic aerogel granule has low density and is incompatible with water, the single hydrophobic aerogel granule floats on water. Therefore, the single hydrophobic aerogel granule is difficulty distributed in post-processing. The single hydrophilic aerogel granule can absorb water. After the water absorption, the pores of the single hydrophilic aerogel granule are filled with water and thus the single hydrophilic aerogel granule precipitates in water. As such, air in the pores of the single hydrophilic aerogel granule disappears so that the single hydrophilic aerogel granule loses the heat isolation property after dispersion. The aerogel granule of the present invention has a hydrophilic outer shell and a hydrophobic inner core. By the hydrophilic outer shell, the aerogel granule of the present invention is compatible with water and evenly distributed in water; by the hydrophobic inner core, water can't penetrate into the aerogel granule of the present invention. The inventive product is evenly distributed and evenly floats on water and its inner still contains air after the dispersion. That is, the inventive product still exhibits the heat isolation property after dispersion in a hydrophilic solvent.

(23) As shown in FIGS. 3A and 3B, an aerogel granule having a hydrophobic outer shell and a hydrophilic inner core, a single hydrophilic aerogel granule, and a single hydrophobic aerogel granule are added to toluene. Since the single hydrophilic aerogel granule and the single hydrophobic aerogel granule both absorb toluene and air in pores of each aerogel granule disappears, each aerogel granule precipitates in toluene. Specifically, the precipitation of the single hydrophobic aerogel is even without aggregation, and the precipitation of the single hydrophilic aerogel is uneven with aggregation. The aerogel granule of the present invention has a hydrophobic outer shell and a hydrophilic inner core. By the hydrophobic outer shell, the aerogel granule of the present invention is compatible with toluene and evenly distributed in toluene; by the hydrophilic inner core, toluene can't penetrate into the aerogel granule of the present invention. The inventive product is evenly distributed and evenly floats on toluene and its inner still contains air after the dispersion. That is, the inventive product still exhibits the heat isolation property after dispersion in a hydrophobic solvent.

(24) As shown in FIG. 4, a surface-hydrophilic aerogel granule is shown under a scanning electron microscope (SEM) at various magnifications. The aerogel granule is a semispherical aerogel granule; it has a compact hydrophilic structure (as indicated by the black arrow) on its outer surface, and a loose hydrophobic structure (as indicated by the white arrow) in its inner.

(25) As shown in FIG. 5, a surface-hydrophobic aerogel granule is shown under a scanning electron microscope at various magnifications. The aerogel granule is a spherical aerogel granule; it has a loose hydrophobic structure (as indicated by the black arrow) on its outer surface, and a compact hydrophilic structure (as indicated by the white arrow) in its inner.

(26) 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.