CN1308233C

CN1308233C - Process for preparing amphiphilic nano silicon dioxide

Info

Publication number: CN1308233C
Application number: CNB2005100189724A
Authority: CN
Inventors: 张超灿; 吴力立; 金小刚; 李曦
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2005-06-23
Filing date: 2005-06-23
Publication date: 2007-04-04
Anticipated expiration: 2025-06-23
Also published as: CN1724352A

Abstract

The present invention relates to a preparation method of nanometer SiO2, which comprises the steps as follows: filtering sodium silicate to remove impurities; under the existence of an amphiphilic block polyether silanol compound, exchanging cations by cation exchange resin of polystyrenes, and exchanging anions by anion exchange resin of polystyrenes; adding a NaOH solution and regulating the pH value; making the solution stand, heating and then cooling the solution to room temperature; ultra filtering and concentrating the solution with ultrafiltration membrane to prepare an amphiphilic nanometer SiO2 dispersion with the average particle diameter of 10 to 50 nm. The nanometer silicon dioxide in the dispersion is provided with amphiphilic block polyether on the particle surface, is stable in acidic condition and alkaline condition without aggregation, and can be dispersed in aqueous and oily architecture in the nanometer scale.

Description

Preparation method of amphiphilic nano silicon dioxide

Technical Field

The invention relates to amphiphilic nano SiO₂The preparation method of (1).

Background

Nano SiO₂Has wide application, and almost all the original SiO is applied₂The industry of powder.

At present, the nano SiO₂The preparation method of the composite material comprises a dry method and a wet method. The dry method includes a gas phase method and an arc method, a wet precipitation method and a gel method.

The gas phase method mostly takes silicon tetrachloride as a raw material, and adopts silicon tetrachloride gas to hydrolyze at the high temperature of oxyhydrogen gas flow to prepare fumed silica. The method has expensive raw materials, high energy consumption, complex technology and high equipment requirement, which limits the use of products.

The gel method is to add acid to reduce the alkalinity and induce the polymerization reaction of silicate, so that the particle diameter of high polymeric silicate ions existing in the form of colloidal particles in the system is increased continuously to form silica sol with opalescence. After forming sol, with the further reduction of the pH value ofthe system, OH is adsorbed^-Negatively charged SiO₂The electromotive potential of the colloidal particles is correspondingly reduced, the stability of the colloidal particles is reduced, and SiO is generated₂The colloidal particles pass through the surface adsorbed hydrated Na⁺The silicon gel is formed by coagulation through the bridging action of the nano-powder, and the nano-powder is obtained after dehydration. The raw materials of the method are the same as those of the precipitation method, but gel is formed instead of directly generating precipitation, and then the gel is dried and dehydrated, so that the product has the characteristics similar to those of a dry product, the price is cheaper than that of the dry product, but the process is more complex than that of the precipitation method, and the cost is also higher. The method is less applicable.

The precipitation method is to obtain loose, finely dispersed SiO precipitated in flocculent structure by acidification of the silicate₂And (4) crystals. The method has the advantages of easily available raw materials, simple production flow, low energy consumption and low investment, but the product quality is not as good as that of products adopting a gas phase method and a gel method. The method is the main production method at present.

Because of the dry method for preparing the nano SiO₂High cost, difficult popularization and wet preparation of nano SiO₂The flocculation drying process of (a) causes the nano silica particles having a huge specific surface area to agglomerate and be difficult to redisperse. Therefore, the high-dispersibility nano SiO₂Preparation remainsa difficult problem to solve.

The main component of silica sol is also silica, the particle size of its dispersoid in water is also in the nanoscale range. Silica sols can be prepared by ion exchange: the ion exchange method is also called as a particle growth method, and the silica sol production method adopts water glass as a raw material to prepare a silica sol product through the processes of ion exchange reaction, seed crystal preparation, particle growth reaction, concentration step, purification step and the like.

However, the silica particles of the silica sol exist in a state of hydrosol, and the surface of the silica sol is combined with a large amount of water and charges, so that the stability is greatly influenced by pH and is easy to agglomerate. Therefore, it is difficult to apply the silica in the silica sol to lipophilic materials such as polymers in a nano-dispersion scale.

The typical preparation and modification method of the nano silicon dioxide comprises the following steps: CN94104007 discloses a method for preparing ultrafine monodisperse hydrophobic silica particles, which utilizes and controls the hydrolysis of ethyl silicate to obtain hydrophobic nano silica particles; CN97125800 describes a process for preparing nano-silica from alkali metal silicates, resulting in porous silica particles; EP0987219 describes the preparation of ultrafine silica; AT391122B describes the preparation of silica hydrosols. The nano silicon dioxide products prepared by the methods have hydrophobicity or hydrophilicity and higher production cost, and the preparation methods of the amphiphilic nano silicon dioxide are rare.

Disclosure of Invention

The invention aims at the prior art to solve the problem of nano SiO₂Provides a new way for preparing nano-silicon dioxide, and the nano-SiO prepared by the method₂The dispersion can be realized uniformly in an aqueous phase (polar solvent phase) and can also be realized uniformly in an oil phase (non-polar solvent phase) and a polymer matrix.

The invention prepares nano SiO by ion exchange method₂In the in-situ system of (A), optionally adding SiO₂Block polyether silanol with surface hydroxyl reacted through block polyether silanol and SiO₂The surface hydroxyl of (2) reacts to make the nano SiO₂The surface of the nano SiO film is provided with amphiphilic polyether groups₂The particle size is distributed between 10nm and 50nm, and the nano SiO is acted by hydrophilic groups on the surface of the nano SiO₂Can be uniformly distributed in water phase, and the nano SiO is acted by lipophilic groups on the surface₂Can be uniformly distributed in the oil phase.

The detailed technical scheme of the invention is as follows:

filtering impurities from sodium silicate (water glass) with the modulus of 3.4 and the content of 3-10%, performing ion exchange by polystyrene cation exchange resin in the presence of an amphiphilic block polyether silanol compound until the pH value of the liquid reaches 2-3, performing ion exchange by polystyrene anion exchange resin until the pH value of the liquid reaches 4-6, adding NaOH solution, adjusting the pH value to be 8.5-10.5, standing for 12-24 hours, heating at 60-80 ℃ for 2-6 hours, cooling to room temperature, performing ultrafiltration concentration by an ultrafiltration membrane with the molecular weight of 2-5 ten thousand until the solid content is 20-35%, and obtaining the nano silicon dioxide dispersion liquid modified with the amphiphilic block polyether silanol and monodisperse particles on the surface. Nano SiO in the nano liquid₂The particle size of the particles is 10-50 nm, the performance is stable under acidic and alkaline conditions, and no precipitation phenomenon occurs.

Wherein the dosage of the amphiphilic block polyether silanol compound is 0.5-5% (mass ratio) of sodium silicate, and the molecular formula is as follows:

wherein x is in the range of 12 to 120, and y is in the range of 10 to 100. The hydrophilic section is polyethylene oxide section, the lipophilic section is polypropylene oxide section, and the hydrophilic section and the lipophilic section are connected by methyl silanol.

The silanol group in the block polyether silanol compound is subjected to chemical reaction with-OH groups on the silicon dioxide in situ while the silicon dioxide is generated, so that stable Si-O-Si covalent bonds are synchronously generated, the nano silicon dioxide modified with the block polyether on the surface is directly prepared in one step, and the agglomeration of the nano silicon dioxide is effectively prevented. The block polyether chain in the block polyether silanol compound is an amphiphilic polymer chain which is combined to the nano SiO through silanol₂After the surface of the particles is finished, the surface of the silicon dioxide nano particles simultaneously has hydrophilic groups and lipophilic groups, and the amphipathy enables the nano silicon dioxide particles to be dispersed in water and extracted by oily organic monomers, so that the application field of the nano silicon dioxide particles is greatly expanded.

The preparation method has the beneficial effects that the prepared nano SiO with the particle size distribution of 10-50 nm and capable of being uniformly distributed in water phase and oil phase₂The reaction condition is mild, and the cost is low. Compared with the preparation method of various nano silicon dioxide powder, the preparation method has the advantages that: the method avoids the drying process of preparing powder by a wet method, is directly applied in a liquid medium dispersion mode, greatly reduces the agglomeration of nano particles, and has low cost.

Detailed description of the preferred embodiments

The present invention will be further described with reference to the following examples.

Example 1: filtering out impurities with 3% sodium silicate (water glass) with modulus of 3.4, and adding amphiphilic block polyether silanol compound in the presence of 0.5% of sodium silicatePercent, the x value of the block polyether silanol is 12, and the y value is 10. Performing ion exchange with polystyrene cation exchange resin until pH of the liquid reaches 2, performing ion exchange with polystyrene anion exchange resin until pH of the liquid reaches 4, adding NaOH solution, adjusting pH to 8.5, standing for 12 hr, heating at 60 deg.C for 6 hr, cooling to room temperature, ultrafiltering and concentrating with ultrafiltration membrane having molecular weight of 5 ten thousand to obtain amphiphilic nanometer SiO with average particle diameter of 50nm and solid content of 20%₂The dispersion liquid has stable performance under acidic and alkaline conditions, and can be dispersed in ethanol, acetone and methyl methacrylate in a nanometer scale.

Example 2: after filtering impurities from sodium silicate (water glass) with the modulus of 3.4 and the content of 10%, in the presence of an amphiphilic block polyether silanol compound, wherein the dosage of the amphiphilic block polyether silanol compound is 5% of the sodium silicate, the x value of the block polyether silanol is 120, and the y value is 100. Performing ion exchange with polystyrene cation exchange resin until pH of the liquid reaches 3, performing ion exchange with polystyrene anion exchange resin until pH of the liquid reaches 6, adding NaOH solution, adjusting pH to 10.5, standing for 24 hr, heating at 80 deg.C for 2 hr, cooling to room temperature, ultrafiltering and concentrating with ultrafiltration membrane having molecular weight of 4 ten thousand to obtain amphiphilic nanometer SiO with average particle size of 30nm and solid content of 35%₂The dispersion liquid has stable performance under acidic and alkaline conditions, and can be dispersed in water, toluene and styrene in a nanometer scale.

Example 3: after impurities are filtered by sodium silicate (water glass) with the modulus of 3.4 and the content of 5 percent, in the presence of an amphiphilic block polyether silanol compound, wherein the dosage of the amphiphilic block polyether silanol compound is 2 percent of the sodium silicate, the x value of the block polyether silanol is 60, and the y value is 50. Performing ion exchange with polystyrene cation exchange resin until pH of the liquid reaches 3, performing ion exchange with polystyrene anion exchange resin until pH of the liquid reaches 5, adding NaOH solution, adjusting pH to 9, standing for 24 hr, heating at 80 deg.C for 2 hr, cooling to room temperature, ultrafiltering and concentrating with ultrafiltration membrane having molecular weight of 2 ten thousand to solid content of 30% to obtain amphiphilic nano SiO with average particle size of 10nm₂The dispersion liquid has stable performance under acidic and alkaline conditions, and can be dispersed in ethanol, acetone, ethyl acetate, toluene, styrene and methyl methacrylate in a nano scale.

Claims

1. Nano S_iO₂The preparation method is characterized in that after impurities are filtered out bysodium silicate, in the presence of an amphiphilic block polyether silanol compound, cation exchange is carried out by polystyrene cation exchange resin, anion exchange is carried out by polystyrene anion exchange resin, NaOH solution is added, the pH value is adjusted, after standing, heating is carried out, cooling is carried out to room temperature, and nano silicon dioxide dispersion liquid with amphiphilic block polyether silanol modified on the surface and monodisperse particles and average particle size of 10-50 nm is obtained through ultrafiltration concentration by an ultrafiltration membrane.

2. The preparation method of claim 1, wherein the modulus of the sodium silicate is 3.4, the content is 3-10%, the sodium silicate is subjected to ion exchange by polystyrene cation exchange resin in the presence of an amphiphilic block polyether silanol compound until the pH value of the liquid reaches 2-3, then the polystyrene anion exchange resin is subjected to ion exchange until the pH value of the liquid reaches 4-6, NaOH solution is added to adjust the pH value to 8.5-10.5, the mixture is kept stand for 12-24 hours, heated at 60-80 ℃ for 2-6 hours, cooled to room temperature, and concentrated by ultrafiltration membrane ultrafiltration with molecular weight of 2-5 ten thousand until the solid content is 20-35%, wherein the addition amount of the block polyether silanol is 0.5-5% of the mass ratio of the sodium silicate.

3. The process according to claim 1, wherein the amphiphilic block polyether silanol used is a two-stage block polyether of the formula:

the value of x is within the range of 12-120, the value of y is within the range of 10-100, the hydrophilic section is a polyethylene oxide section, the lipophilic section is a polypropylene oxide section, and the hydrophilic section and the lipophilic section are connected by methyl silanol.