CN105621419A

CN105621419A - Ambient preparation method for silica aerogel powder

Info

Publication number: CN105621419A
Application number: CN201410715487.1A
Authority: CN
Inventors: 任富建; 赵耀耀; 杨万吉; 李路明
Original assignee: BCEG Advanced Construction Materials Co Ltd
Current assignee: BCEG Advanced Construction Materials Co Ltd
Priority date: 2014-12-02
Filing date: 2014-12-02
Publication date: 2016-06-01

Abstract

An ambient preparation method for silica aerogel powder is a method which utilizes water glass as a silicon source to prepare silica aerogel powder by the ambient drying technology and comprises the following steps: diluting water glass into a solution of different multiples by water; performing acid catalysis to form a gel; aging for a certain period of time under the action of an ageing solution; then carrying out water washing, solvent displacement, surface hydrophobic modification and solvent cleaning; drying under the ambient condition to obtain silica aerogel powder of a three-dimensional network structure. The aerogel powder has the density of 110-140 kg/m<3>, the specific surface area of 540-760 m<2>/g, and the 25 DEG C heat conductivity of 0.012-0.017 W/(m.k). The ambient preparation method for silica aerogel powder improves the wet gel displacement efficiency, reduces contraction and cracking of aerogel, realizes radical cleaning of residues in aerogel, and finally obtains the silica aerogel powder which can realize industrial mass production.

Description

A kind of atmospheric preparation method of silicon dioxide aerogel powder

Technical field

The invention belongs to field of inorganic materials, be a kind of typical meso-porous nano material, be suitable as heat-insulating heat-preserving material, be particularly suitable for the aerosil field of high temperature insulating and low temperature cold insulation.

Background technology

Aeroge is a kind of inorganic mesoporous material, and its framing structure is by the grain of 2��5nm molecular diameter space multistory network structure between 20��200nm. Aeroge is to be currently known the solid material that density is minimum, there is high-specific surface area, low optical refractive index, low acoustic propagation velocity, low thermal conductivity, do not burn, the excellent performance such as high temperature resistant, can be widely applied to the field such as high temperature and the heat insulation field of low temperature, space field, catalyst load.

Mainly there are tetraethyl orthosilicate, waterglass etc. in the silicon source preparing aerosil, and along with the raising of the development of water technology and solvent isolation technics, waterglass is prepared aeroge and increasingly had advantage with its low cost, the advantage such as nontoxic. And constant pressure and dry technique has that equipment investment is little, maintenance cost is low, production safety, can be continuous drying etc. feature become the main method producing aerogel particle.

Invention CN103818912A adopts waterglass to be that density is prepared at 120kg/m in silicon source³Aerosil, but wet gel does not use organic solvent to clean after modification, has remained hydrophobically modified reagent and by-product thereof, and the density increasing aeroge has remained corrosive by-product simultaneously. Invention CN102557052A uses microwave exposure to carry out PhastGel in gel process; it is prepared for low-density aeroge; do not take into account the production aerosil of serialization and scale; in gel preparation course, solvent displacement number of times is few; displacement is not thorough, the substantial amounts of hydrophobically modified reagent of water consumption of residual.

Waterglass constant pressure and dry is prepared gel in aerogel process and is easily shunk and ftracture, and gel begins to shrink in aging and replacement process. The surface tension of the existence between gel skeleton and solvent, produces capillary pressure in dry run, is the main cause causing aeroge to shrink and ftracture. Although patent and document refer to many methods utilizing waterglass to prepare aerosil, but still there are some problems, how to make solvent displacement thoroughly, how to solve the residue impact on aeroge after hydrophobically modified, and how dry run is avoided shrink and the problem etc. of cracking.

Summary of the invention

It is an object of the invention to use cheap waterglass is raw material, through constant pressure and dry a kind of aerosil of preparation, the problem solving to run in general aeroge preparation process, and can industrialization, produce on a large scale.

The present invention provides a kind of waterglass to be the method that aerosil is prepared in silicon source, and its step is as follows:

(1) preparation of gel: waterglass joins in the water of 5��10 times, stirs, carries out ion exchange by the colloidal sol after dilution with isopyknic cation exchange resin, obtains pH solution between 2��3, adds alkali and regulates pH value of solution between 6��8; When not adopting cation exchange resin, waterglass dilute solution adds the acid solution of 2mol/L, regulate between pH to 6��9, gel after 2��60min, obtain hydrogel;

(2) gel is aging: adopt the waterglass diluent with method 1 equal in quality mark as Ageing solution, or the alcoholic solution of employing mass fraction 2%��20% tetraethyl orthosilicate is as Ageing solution, aging 6��48h at 25��70 DEG C;

(3) washing: needing to use deionized water to wash without the wet gel of resin cation exchange, use the deionized water of 1��3 times of volume to wash, washing temperature is between 20��60 DEG C, and washing time, at 6��18h, is washed 2��8 times;

(4) solvent displacement: use the organic solvent of 0.5��2 times to carry out solvent displacement, displacement temperature is maintained between 40��60 DEG C, time is at 3��12h, replacing 2��6 times, wherein the organic solvent for replacing can be one or more mixture of ethanol, isopropanol, normal hexane, normal heptane, acetone etc.;

(5) hydrophobically modified: add the organic solution of 5%��20% hydrophobically modified reagent of 0.5��2 times of volume, pour into equipped with in wet gel container, hydrophobically modified temperature is 40��60 DEG C, modified 12��48h when stirring, the organic solvent that the solvent of hydrophobically modified reagent adopts with solvent displacement is identical, the hydrophobically modified reagent wherein adopted is trim,ethylchlorosilane (TMCS), hexamethyldisiloxane (HMDZ), hexamethyl disiloxane (HMDSO), MTMS (MTES), one or more mixture in trimethyl ethyoxyl silicon (TMES),

(6) solvent clean: adopt the organic solvent identical with solvent displacement that modified organogel is carried out, the volume of cleaning solvent and wet gel volume ratio are between 0.5��2, modification temperature, between 40��60 DEG C, cleans 2��6 times, cleans 4��12h every time;

(7) constant pressure and dry: adopt constant pressure and dry that wet gel is dried, the wet gel prepared is put in convection oven, dry 24��48h in room temperature��50 DEG C, it is warmed up to 150��200 DEG C of dry 1��3h more afterwards.

Detailed description of the invention

Embodiment 1

After waterglass, deionized water, 2mol/L hydrochloric acid being mixed according to the ratio of volume ratio 1: 10: 1, stand gel; Aged at room temperature 24h; Using and soak wet gel with the isopyknic deionized water of wet gel, magnetic agitation Water Under is washed 3 times, each 12h; Wet gel is put in the ethanol of same volume, under room temperature, carry out alcohol water displacement, replace 3 times under stirring condition, each 12h; The alcohol mixeding liquid adding the trim,ethylchlorosilane of 20% under room temperature carries out the modified 24h of surface hydrophobicity; Add and the isopyknic ethanol purge of wet gel 3 times, each 12h; Being put into by aeroge at 50 DEG C of dry 12h in baking oven, dry 2h at 150 DEG C, obtaining aerosil density is 132kg/m³, specific surface area is 580m²/ g, 25 DEG C of heat conductivitys of its powder body are 0.016W/ (m K).

Embodiment 2

By waterglass, deionized water with after the volume ratio mix homogeneously of 1: 10 again with isopyknic cation exchange resin mix and blend 20min, be filtrated to get the colloidal sol that pH is 2��3, the ammonia adding 2mol/L is adjusted to pH=7, stands gel. Processing method after gel is identical with embodiment 1, obtains aerosil density 139kg/m³, specific surface area is 543m²/ g, 25 DEG C of heat conductivitys of its powder body are 0.017W/ (m K).

Embodiment 3

After waterglass, deionized water, 2mol/L hydrochloric acid being mixed according to the volume ratio of 1: 8: 1, stand gel; Add the alcoholic solution of TEOS of 5% as Ageing solution, aging 24h at 50 DEG C; Add and soak wet gel with the isopyknic deionized water of wet gel, wash 3 times for 50 DEG C when magnetic agitation, each 12h; Add and the isopyknic normal hexane of wet gel, at 50 DEG C, carry out alcohol water displacement, replace 3 times under stirring condition, each 12h; Adding the normal hexane mixed solution of isopyknic 20% trim,ethylchlorosilane, carry out surface hydrophobicity and modifiy at 50 DEG C, modification time is 24h; Add equal-volume normal hexane, clean 3 times at 50 DEG C, each 12h; Being put into by aeroge at 50 DEG C of dry 12h in baking oven, dry 2h at 150 DEG C, obtaining aerosil density is 117kg/m³, specific surface area is 760m²/ g, 25 DEG C of heat conductivitys of its powder body are 0.012W/ (m K).

Embodiment 4

By waterglass, deionized water, 2mol/L hydrochloric acid according to, after the mixed in molar ratio of 1: 6: 1, standing gel; Add the alcoholic solution of TEOS of 5% as Ageing solution, aging 24h at 50 DEG C; Using isopyknic deionized water to soak wet gel, lower 50 DEG C of stirring condition is washed 3 times, each 12h; Re-use isopyknic normal hexane at 50 DEG C, carry out alcohol water displacement, replace 3 times under stirring condition, each 12h; Add the normal hexane mixed liquor that isopyknic mass fraction is 10% hexamethyldisiloxane at 50 DEG C and carry out the modified 24h of surface hydrophobicity; Clean 3 times with wet gel equal-volume normal hexane at 50 DEG C, each 12h; Being put into by aeroge at 50 DEG C of dry 12h in baking oven, dry 2h at 150 DEG C, obtaining aerosil density is 112kg/m³, specific surface area is 725m²/ g, 25 DEG C of heat conductivitys of its powder body are 0.012W/ (m K).

Embodiment 5

By waterglass, deionized water be mixed with isopyknic cation exchange resin after the ratio mix homogeneously of 1: 6 even after, be filtrated to get the colloidal sol that pH is 2��3, the ammonia adding 2mol/L is adjusted to pH=7, stands gel. Processing method after gel is identical with embodiment 4, and obtaining aerosil density is 115kg/m³, specific surface area is 673m²/ g, 25 DEG C of heat conductivitys of its powder body are 0.013W/ (m K).

Claims

1. an atmospheric preparation method for silicon dioxide aerogel powder, is characterized in waterglass (NaO₂��nSiO₂) for silicon source, after the deionized water of different volumes ratio dilutes, carry out gel using acid for catalyst or adopt cationic resin after removing sodium ion, to use the alkali such as ammonia, sodium hydroxide to carry out gel as catalyst, the hydrogel obtained is aging through Ageing solution, sodium ion is removed in washing, organic solvent is used to carry out solvent displacement, reduce the surface tension between hole and solvent, use hydrophobically modified reagent to carry out surface hydrophobicity to modifiy, use organic solvent to clean modifying agent and the by-product of residual, obtain aerosil through constant pressure and dry.

2. the atmospheric preparation method of a kind of silicon dioxide aerogel powder described according to claim 1, is characterized in that: described silicon source is waterglass, and its modulus n is 2.2��3.7.

3. the atmospheric preparation method of a kind of silicon dioxide aerogel powder described according to claim 1, it is characterized in that: catalyst can be the hydrochloric acid of 1��3mol/L, sulphuric acid or oxalic acid, Ageing solution is ethanol or the hexane solution of the tetraethyl orthosilicate of 2%��20%, and solvent displacement and the organic solvent cleaning residual modifying agent use can be one or more mixed solvents such as ethanol, acetone, isopropanol, propanol, normal hexane, normal heptane.

4. the atmospheric preparation method of a kind of silicon dioxide aerogel powder described according to claim 1, is characterized in that: during gel, the pH of solution is between 6��8.5, and the baking temperature of wet gel is between 30��200 DEG C.

5. the atmospheric preparation method of a kind of silicon dioxide aerogel powder described according to claim 1, is characterized in that: hydrophobically modified reagent is one or more mixture in trim,ethylchlorosilane (TMCS), hexamethyldisiloxane (HMDZ), hexamethyl disiloxane (HMDSO), MTMS (MTES), trimethyl ethyoxyl silicon (TMES).