阅读说明：本技术 一种二氧化硅纳米气凝胶纤维的制备方法 (Preparation method of silicon dioxide nano aerogel fiber ) 是由 吴长征 谢毅 于 2020-08-04 设计创作，主要内容包括：本发明提供了一种二氧化硅纳米气凝胶纤维的制备方法,包括：A)将水玻璃溶液和酸性溶液混合,得到酸性硅酸钠溶液；B)将酸性硅酸钠溶液采用针头注入至氨水溶液中固化,过滤得到硅酸纤维；C)将硅酸纤维采用改性剂溶液改性,过滤、干燥得到二氧化硅纳米气凝胶纤维。本发明使用廉价的无机水玻璃为硅前驱体,采用将酸性硅酸钠溶液采用针头注入至氨水溶液中直接挤出固化的反相法制备硅酸纤维后改性制备气凝胶纤维,具有易于大规模生产,批次稳定性较好等优点。本发明工艺所制备的气凝胶纤维可以独立成型,无需加入其他纤维增强,隔热性能大大增强。(The invention provides a preparation method of silicon dioxide nano aerogel fibers, which comprises the following steps: A) mixing the water glass solution and the acid solution to obtain an acid sodium silicate solution; B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers; C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers. According to the invention, cheap inorganic water glass is used as a silicon precursor, and the aerogel fiber is prepared by modifying after silicic acid fiber is prepared by adopting an inverse method of injecting an acidic sodium silicate solution into an ammonia water solution by using a needle and directly extruding and curing, so that the aerogel fiber has the advantages of easiness in large-scale production, good batch stability and the like. The aerogel fiber prepared by the process can be independently formed without adding other fibers for reinforcement, and the heat insulation performance is greatly enhanced.)

1. A method for preparing silica nano aerogel fibers is characterized by comprising the following steps:

A) mixing the water glass solution and the acid solution to obtain an acid sodium silicate solution;

B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers;

C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers.

2. The method according to claim 1, wherein the acid is one or more of sulfuric acid, hydrochloric acid, nitric acid, or acetic acid.

3. The preparation method according to claim 1, characterized in that the mass percentage of the silicon dioxide in the acidic sodium silicate solution is 3-20%; the pH value of the acidic sodium silicate solution is 3-6.

4. The method according to claim 1, wherein the aqueous ammonia solution has a mass concentration of 5 to 20%.

5. The method of claim 1, wherein the needle size is 10 to 200 microns; the injection speed is 1-5 m/min.

6. The preparation method according to claim 1, wherein the filtration in step B) is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration; and C, filtering is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration.

7. The method of claim 1, wherein the modifier solution of step C) comprises hexamethyldisiloxane, ethanol, and hydrochloric acid; the mass ratio of the silicic acid fiber to the ethanol to the hydrochloric acid to the hexamethyldisiloxane is 1: (0.01-0.1): (0.01-0.04): 1.

8. the preparation method according to claim 1, wherein the modification in step C) is specifically heating, mixing and stirring; the heating temperature is 40-80 ℃; the stirring speed is 70rpm to 100 rpm; the stirring time is 30-120 min.

9. The preparation method of claim 1, wherein the drying temperature in the step C) is 80-250 ℃, and the drying time is 3 min-1 h.

10. The preparation method according to claim 1, wherein the silica nano aerogel fiber has a density of 0.05g/ml to 0.3g/ml and a specific surface area of 100m²/g～400m²The thermal conductivity is between 0.012W/mk and 0.1W/mk.

Technical Field

The invention relates to the technical field of aerogel preparation, in particular to a preparation method of silicon dioxide nano aerogel fibers.

Background

Aerogel material is a light porous solid material obtained by replacing the solvent in the gel with air under the condition of keeping the skeleton of the gel unchanged, and the porosity of the aerogel material can reach more than 95 percent, so that the aerogel is also the solid material with the lightest known mass at present. Aerogel is the solid material with the best heat insulation performance in the world at present, and is the heat insulation material closest to vacuum. The method is widely applied to the fields of building heat preservation, industrial heat preservation, new energy automobiles and electronic heat management. Meanwhile, the aerogel has many excellent physical and chemical properties, such as low density, low sound velocity transmittance, high adsorption rate and the like, so that the aerogel is widely applied to various fields of national life.

The current preparation method of the aerogel mainly comprises two methods of supercritical drying and normal pressure drying. Supercritical drying is to heat and pressurize the solution in the gel pore canal to a supercritical state, in which the interface of the liquid and the gas disappears and the capillary force does not exist. However, the pressure and temperature of the supercritical point of the liquid are relatively high, for example, the supercritical point of methanol is 239.4 ℃ and nearly 81 atmospheres, and the high pressure and temperature make the aerogel preparation equipment expensive, difficult to operate, high in cost and dangerous for explosion leakage. The normal pressure drying method does not need high temperature and high pressure, and has safe operation and low cost. The normal pressure drying firstly uses a low surface tension solvent (such as n-hexane) to replace an original high surface tension solvent (such as water) in a gel pore channel by solvent exchange, and simultaneously performs inert modification on groups on the surface of the gel pore channel to modify hydroxyl with higher activity on the surface of the gel pore channel into chemically inert silicon methyl, so that the hydroxyl condensation caused by gel volume shrinkage in the drying process can be prevented. The aerogel material prepared by drying under normal pressure by the method can achieve supercritical drying on the structure and the performance.

The traditional aerogel material has low strength due to very high porosity, and generally needs to be reinforced by using a fiber material, and the addition of the fiber phase can influence the heat-insulating property of the aerogel, so that the aerogel cannot achieve the optimal heat-insulating effect.

Disclosure of Invention

In view of this, the technical problem to be solved by the present invention is to provide a method for preparing silica nano aerogel fiber, which has the characteristics of light weight, high strength, high specific surface area and low cost.

The invention provides a preparation method of silicon dioxide nano aerogel fibers, which comprises the following steps:

A) mixing the water glass solution and the acid solution to obtain an acid sodium silicate solution;

B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers;

C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers.

Preferably, the acid is one or more of sulfuric acid, hydrochloric acid, nitric acid or acetic acid.

Preferably, the mass percentage of the silicon dioxide in the acidic sodium silicate solution is 3-20%; the pH value of the acidic sodium silicate solution is 3-6.

Preferably, the mass concentration of the ammonia water solution is 5-20%.

Preferably, the needle head size is 10-200 microns; the injection speed is 1-5 m/min

Preferably, the filtration in step B) is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration; and C, filtering is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration.

Preferably, the modifier solution of step C) comprises hexamethyldisiloxane, ethanol and hydrochloric acid; the mass ratio of the silicic acid fiber to the ethanol to the hydrochloric acid to the hexamethyldisiloxane is 1: (0.01-0.1): (0.01-0.04): 1.

preferably, the modification in the step C) is heating, mixing and stirring; the heating temperature is 40-80 ℃; the stirring speed is 70rpm to 100 rpm; the stirring time is 30-120 min.

Preferably, the drying temperature in the step C) is 80-250 ℃, and the drying time is 3 min-1 h.

Preferably, the density of the silicon dioxide nano aerogel fiber is 0.05g/ml to 0.3g/ml, and the specific surface area is 100m²/g～400m²The thermal conductivity is between 0.012W/mk and 0.1W/mk.

Compared with the prior art, the invention provides a preparation method of silicon dioxide nano aerogel fiber, which comprises the following steps: A) mixing the water glass solution and the acid solution to obtain an acid sodium silicate solution; B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers; C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers. According to the invention, cheap inorganic water glass is used as a silicon precursor, and the aerogel fiber is prepared by modifying after silicic acid fiber is prepared by adopting an inverse method of injecting an acidic sodium silicate solution into an ammonia water solution by using a needle and directly extruding and curing, so that the aerogel fiber has the advantages of easiness in large-scale production, good batch stability and the like. The aerogel fiber prepared by the process can be independently formed without adding other fibers for reinforcement, and the heat insulation performance is greatly enhanced.

Drawings

FIG. 1 is a schematic diagram of an apparatus for preparing silicic acid fiber according to the present invention;

FIG. 2 is a specific surface area diagram of aerogel fibers prepared in example 1 of the present invention;

FIG. 3 is a graph of the pore size distribution of aerogel fibers prepared in example 1 of the present invention.

Detailed Description

The invention provides a preparation method of silicon dioxide nano aerogel fiber, and the technical personnel in the field can use the content for reference and appropriately improve the process parameters for realization. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope of the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.

The invention provides a preparation method of silicon dioxide nano aerogel fibers, which comprises the following steps:

A) mixing the water glass solution and the acid solution to obtain an acid sodium silicate solution;

B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers;

C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers.

The invention provides a preparation method of silicon dioxide nano aerogel fiber, which comprises the steps of mixing a water glass solution and an acid solution to obtain an acid sodium silicate solution.

The invention firstly prepares the water glass solution, namely: mixing water glass and purified water to obtain a uniform solution; the mixing time is not limited, and can be 20-30 min. The mixing vessel in the present invention is not limited, and is preferably a stirred tank.

The invention does not limit the water glass, and the water glass is well known to those skilled in the art; the water glass may preferably have a silica content of 30%, and a modulus of 2.4.

The invention uses cheap inorganic water glass as a silicon precursor, and has larger cost advantage compared with an organic silicon precursor.

And after preparing the water glass solution, mixing the water glass solution with the acid solution to obtain the acid sodium silicate solution.

According to the invention, the acid is one or more of sulfuric acid, hydrochloric acid, nitric acid or acetic acid; the present invention is not limited to the source, and may be commercially available. The concentration of the acid solution is 30 to 60 percent

The mass percentage of the silicon dioxide in the acidic sodium silicate solution is preferably 3-20%; more preferably 5% to 18%. The pH value of the acidic sodium silicate solution is 3-6; more preferably specifically 3, 4, 5, 6 or any point value in between.

The modulus of the sodium silicate aqueous solution is between 2.5 and 3.3 (namely SiO in the solution)₂And Na₂Molar ratio of O).

After the acid sodium silicate solution is obtained, injecting the acid sodium silicate solution into the ammonia water solution by using a needle head for solidification.

The present invention preferably employs the apparatus described in fig. 1 for making the silicic acid fiber. FIG. 1 is a schematic diagram of an apparatus for preparing silicic acid fiber according to the present invention;

wherein 101 is a needle, 102 is a needle head, 103 is an extruded acid sodium silicate solution, 104 is an ammonia water solution, and 105 is an acid sodium silicate solution.

According to the invention, the acidic sodium silicate solution is extruded into the ammonia water solution by a needle. The material of the needle head is not limited, and the needle head can be extruded mainly, and the size of the needle head is preferably 10-200 micrometers; more preferably 20 to 180 microns; most preferably 30 to 170 microns.

The mass concentration of the ammonia water solution is preferably 5-20%; more preferably 7% to 18%; the injection speed is preferably 1-5 m/min

The invention creatively adopts a mode of extruding and injecting the acidic sodium silicate solution into the ammonia water solution, and can instantly solidify to obtain the silicic acid fiber.

After solidification, silicic acid fiber solid is obtained by filtration. The filtration is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration. The filtration method is not limited in the present invention, and those skilled in the art can understand it.

Modifying silicic acid fiber by using a modifier solution.

The modifier solution comprises hexamethyldisiloxane, ethanol and hydrochloric acid.

Wherein, the improver is hexamethyldisiloxane, the catalyst is hydrochloric acid, and the fluxing agent is ethanol.

According to the invention, the mass ratio of the silicic acid fibers, ethanol, hydrochloric acid and hexamethyldisiloxane is preferably 1: (0.01-0.1): (0.01-0.04): 1; more preferably 1: (0.02-0.09): (0.02-0.04): 1; most preferably 1: (0.02-0.08): (0.02-0.03): 1.

the modification of the invention is specifically heating, mixing and stirring to obtain a mixed solution.

The heating temperature is preferably 40-80 ℃; more preferably 45-75 ℃; most preferably 50-70 ℃; the stirring speed is preferably 70rpm to 100 rpm; more preferably 75rpm to 95 rpm; the stirring time is preferably 30-120 min; more preferably 40-120 min; most preferably 60-120 min.

And then filtering to obtain the modified silicic acid fiber, wherein the filtering is selected from one or more of centrifugal filtration, vacuum filtration or pressure filtration. The filtration method is not limited in the present invention, and those skilled in the art can understand it.

The process adopts the reverse phase method to prepare the silicic acid fiber, and then prepares the aerogel fiber by modifying the silicic acid fiber by the method, and has the advantages of easy large-scale production, good batch stability and the like.

And after modification, drying to obtain the silicon dioxide nano aerogel fiber. Drying the modified silicic acid fiber to obtain the silicon dioxide nanometer aerogel fiber.

According to the invention, the drying temperature is preferably from 80 ℃ to 250 ℃, more preferably from 90 ℃ to 240 ℃, most preferably from 100 ℃ to 230 ℃. The drying time is 3 min-1 h; more preferably 20min to 1 h; most preferably 30min to 1 h.

The aerogel fiber prepared by the process can be independently formed without adding other fibers for reinforcement, and the heat insulation performance is greatly enhanced. The nano-fiber obtained by the invention has the advantages of light weight, high strength, high specific surface, low cost and the like.

The density of the silicon dioxide nano aerogel fiber is 0.05g/ml to 0.3g/ml, and the specific surface area is 100m²/g～400m²The thermal conductivity is between 0.012W/mk and 0.1W/mk.

The invention provides a preparation method of silicon dioxide nano aerogel fibers, which comprises the following steps: A) mixing water glass and an acidic solution to obtain an acidic sodium silicate solution; B) injecting the acidic sodium silicate solution into the ammonia water solution by using a needle for solidification, and filtering to obtain silicic acid fibers; C) modifying silicic acid fibers by adopting a modifier solution, filtering and drying to obtain the silicon dioxide nano aerogel fibers. According to the invention, cheap inorganic water glass is used as a silicon precursor, and the aerogel fiber is prepared by modifying after silicic acid fiber is prepared by adopting an inverse method of injecting an acidic sodium silicate solution into an ammonia water solution by using a needle and directly extruding and curing, so that the aerogel fiber has the advantages of easiness in large-scale production, good batch stability and the like. The aerogel fiber prepared by the process can be independently formed without adding other fibers for reinforcement, and the heat insulation performance is greatly enhanced.

In order to further illustrate the present invention, the following will describe the silica nano aerogel fiber provided by the present invention in detail with reference to the examples.