JPH03183616A - Production of spherical silica - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] C industrial III river use] The present invention relates to a method for producing spherical silica.

(Technology from Fiff) Conventionally, the method for manufacturing LHH silica incorporating a spray drying process is as follows: 1) A solution of an aqueous alkali metal silicate such as sodium silicate is spray-dried. A method of obtaining fine LH fushinrika by treating the resulting fine spherical particles with an acid aqueous solution.

(You can trace it to JP-A-60-54914, JP-A-62-1
2891.6'l;, JP-A-62-128917, etc.).

2) A method of obtaining spherical powder by spray-drying a slurry obtained by dispersing Norica powder in water or an organic medium, and firing the slurry.

(For example, JP-A-61-251509, etc.).

etc. have been proposed.

[Problems to be Solved by the Invention] The above-mentioned conventional methods for producing spherical silica each have the following problems.

Method 1) involves drying the aqueous solution of alkali metal silicate and then returning it to the aqueous system for wet treatment, which wastes a lot of energy. In addition, in this method, when an aqueous solution of alkali metal silicate is sprayed,
In production I, air is trapped in the droplets, and the particles obtained by drying do not form solid spheres but have voids inside. Such voids inside the particles remain even after acid treatment or firing treatment, and air bubbles remain inside the particles of the obtained spherical silica. When silica containing air bubbles is used as a raw material for quartz glass, many air bubbles are mixed into the resulting quartz glass product, making it impossible to obtain a good product.

For this reason, silica containing air bubbles has the disadvantage that its uses are limited.

In method 2), the silica powder is spray-dried after being produced, which lengthens the production process and consumes a large amount of energy.

An object of the present invention is to provide a method for producing solid spherical silica without bubbles through a simplified process.

[Means to solve the problem]

The present inventors conducted research to improve the problems of conventional methods, and completed the present invention based on the knowledge that the above problems can be solved by spraying an aqueous alkali metal silicate solution into acidic gas. .

The present invention relates to the production of spherical silica, which is characterized in that droplets and/or gelled products generated by spraying an aqueous alkali metal silicate solution into an acidic gas are collected, treated with an acid-containing liquid, and then washed with water. The gist is “Method”. The present invention will be explained below.

In the present invention, "spherical" refers to one in which the ratio of the minimum diameter to the maximum diameter in one R element is in the range of 1 to 0.5.

In the method of the present invention, the aqueous alkali metal silicate solution used as a raw material has the general formula; M, 0·n SiO□(
However, M is an alkali metal element, and n is the number of moles of SiO□, which is 0.5 to 5. 8m, an aqueous solution of sodium salt, potassium salt, lithium salt, etc. of silicic acid can be used.

In the method of the present invention, the degree of sjorm in the aqueous alkali metal silicate solution used as a raw material is usually in the range of 5 to 60%, preferably in the range of 20 to 50%. When the 5iOz concentration is low, it takes a long time for the droplets of the aqueous alkali metal silicate solution generated by spraying to solidify, while when the s + o, fi degree is high, the droplets of the aqueous alkali metal silicate solution formed by spraying take a long time to solidify. Increased viscosity makes spraying difficult.

The viscosity of the aqueous alkali metal silicate solution sprayed in the method of the present invention is 200 poise or less, preferably 10 poise or less. If the viscosity is too high, spraying becomes difficult and spherical particles cannot be obtained.

Centrifugal type and two-fluid nozzle type are conventionally known methods for spraying aqueous alkali metal silicate solutions.

Various mechanisms such as a pressure nozzle type and an ultrasonic type can be used, and preferably a centrifugal type or a two-fluid nozzle type is used.

When obtaining particles with a large diameter, a pressure nozzle or a dropping nozzle can be used.

In the method of the invention, an aqueous alkali metal silicate solution is sprayed into an acid gas.

Examples of the acidic gas used in the method of the present invention include gaseous carbon dioxide, sulfurous acid, hydrogen chloride, sulfuric anhydride, etc. Carbon dioxide (carbon dioxide gas) or hydrogen chloride is preferably used.

When a two-fluid nozzle method is adopted as the atomizing method for the aqueous alkali metal silicate solution, the acidic gas can be used as the atomizing gas.

In the method of the present invention, the acidic gas may contain an inert gas such as air. The inert gas concentration in the acidic gas is preferably 10 mol% or less. When the inert gas concentration increases, air bubbles are more likely to be included in the obtained silica particles.

In addition, when obtaining spherical silica used for applications such as desiccants and raw materials for cosmetics, in which there is no problem even if bubbles are included, for example, 78 mol%, or even 90% by mole is added to the acidic gas.
It can contain about mol% of inert gas.

In the method of the present invention, the pressure of the atmosphere in which the aqueous alkali metal silicate solution is sprayed is usually in the range of 0.1 to 100 atm, preferably in the range of 0.9 to 10 atm. Further, the operating temperature is set within a range in which the aqueous alkali metal silicate solution maintains a liquid state with the above-mentioned viscosity, preferably within a range of 10 to 80°C.

The droplets and/or gelled product of the aqueous alkali metal silicate solution generated by spraying are collected by a collection liquid using a wet collection device.

In the method of the present invention, a conventional NW type collection device such as a cyclone scrubber, a venturi scrubber, or a wet wall tower can be used as the collection device, and water or an acid aqueous solution can be used as the collection liquid.

The acid aqueous solution may be acidic water such as the above-mentioned acid gases or organic acids such as nitric acid, or organic acids such as acetic acid or oxalic acid. You can use Yong Nya.

The acid concentration in the acid aqueous solution as the collection liquid is 0.
1 to 4 normal, preferably 0.5 to 3 normal, more preferably 1 to 2 JJ! within a certain range.

The temperature of the collection liquid is not uniquely determined by its composition, but it is recommended to keep it within the range of 10 to 60°C, as gelation of droplets of aqueous alkali metal silicate solution progresses during the wet collection process. , a suspension containing silica particles is obtained. From the obtained suspension, silica particles can be obtained by ordinary solid-liquid separation operations such as filtration, sedimentation, and centrifugation.

In addition, if the droplets of the alkali metal silicate aqueous solution generated by spraying and the acid gas are made to have a high contact pressure and a long contact time, and the droplets of the alkali metal silicate aqueous solution gel, the cyclone It can be collected as silica particles using a dry collection device such as .

The particle size of the droplets and/or gelled product of the aqueous alkali metal silicate solution obtained by spraying in the method of the present invention is approximately 1 μm to 1 μm. As a result, the particle size is 1 to 600.
Spherical silica in the μm range can be obtained.

Although the method of the present invention is not limited by the impurity content in the spherical silica, it is possible to obtain high-purity spherical silica with a low impurity content depending on the intended use of the spherical silica.

In particular, in the case of spherical silica used as a filler for encapsulants in high-density integrated circuit electronic components; ■ Alkali metal elements such as Na and K, alkaline earth metal elements such as Mg and Ca, and halogen elements. The content of each is 1 p
It is preferable that the content of radioactive elements such as 1 and 2 UTh is 11111b or less.

Such high-purity spherical silica with a low impurity content can be obtained by treating the silica particles obtained as described above with an acid-containing liquid and then washing with water to extract and remove impurities.

Acid-containing liquids used in the process to extract and remove impurities include inorganic acids such as carbonic acid, sulfuric acid, hydrochloric acid, and nitric acid;
Examples include aqueous solutions of organic acids such as acetic acid and oxalic acid, and the above collection liquids can also be used.

Furthermore, if necessary, a chelating agent and/or a chelating agent may be added to the acid-containing liquid.
Alternatively, it is possible to add a peroxide such as hydrogen peroxide, or to combine cleaning treatment with an aqueous solution containing these.

The acid concentration of the acid-containing liquid I is 0.1 to 4N, preferably 0.
．． It is in the range of 5 to 3 normal, more preferably 1 to 2 normal.

The processing temperature when extracting and removing impurities is 50°C or higher.
It is good to keep this.

By the above method, the i! ! High purity spherical silica having a content of various impurities such as transfer metal elements of 1 ppm or less can be obtained.

Since the silica thus obtained contains a large amount of water and has a large number of pores, the silica obtained by the above treatment is heat-treated as necessary depending on the intended use of the spherical silica.

Heat treatment conditions vary depending on the use of the spherical silica.
It can be selected as appropriate.

When obtaining spherical silica as a filler for a sealing material for electronic components, heat treatment is performed at a temperature in the range of 100 to 2200'C, preferably firing in a range of 1000 to 1500'C.

This treatment removes moisture remaining in the silica,
Furthermore, the existing silanol groups are reduced to about 0.1ffi1% or less to make the silica particles hydrophobic, and the pores of the silica particles are closed to adjust the pore volume and specific surface area, making the silica particles dense. and change the structure to one that is difficult for moisture to penetrate.

When obtaining spherical silica for use in drying agents, cosmetic raw materials, catalyst supports, liquid chromatography fillers, etc.
Heat treatment at a temperature in the range of 100 to 1050'C is preferable.

As a raw material for glasses such as quartz glass or ceramics, spherical silica without heat treatment can be used, or spherical silica that has been heat treated can be used.

The heating time ranges from 1 second to 100 hours, preferably from 10 seconds to 6 hours, and more preferably from 10 seconds to 3 hours. The combination of temperature and time as heat treatment conditions can be selected as appropriate; the higher the heat treatment temperature is, the shorter the time can be.

The atmosphere in which the heat treatment is performed is arbitrary as long as it does not impair the idea of the present invention, and may be an inert external gas atmosphere such as Ar+LIe,
An oxidizing atmosphere such as air, a reducing atmosphere such as hydrogen, a steam atmosphere, or an atmosphere containing halogen or halide such as chlorine that can effectively remove impurities in silica can be used.

The heat treatment is performed under atmospheric pressure, but can also be performed under reduced pressure.

The heating source is optional; electric heat or combustion gas are economical heat sources. In addition, plasma heating and an image furnace can also be used.

Note that the heat treatment at a low temperature of about 200° C. or lower can also be performed by immersing it in water and hydrothermal treatment.

The spherical silica obtained by heat treatment can be subjected to crushing and classification treatment, if necessary.

The average particle diameter of spherical silica as a filler for electronic component sealing material is in the range of 1 to 100 μm, preferably 5 to 40 μm, and more preferably 10 to 30 μm.

The average particle size of spherical silica as a raw material for quartz glass is 1
~600 μm, preferably 1 to 300 μm, more preferably 1 to 20 μm for sintering, hot pressing, sol-gel method auxiliary materials, etc., and 100 to 300 μm for melting such as arc melting, Herny method, etc. .

〔Effect of the invention〕

By the method of the present invention, solid spherical silica containing no air bubbles can be produced in a simplified process.

By the method of the present invention, high-purity spherical silica is obtained which has a low content of impurities such as alkali (earth M) metal halogens, transition metal elements, and radioactive substances and is suitable as a filler for encapsulants of high-density integrated circuit electronic components. be able to.

〔Example〕

The present invention will be explained below with reference to Examples.

Example-1 Sodium silicate aqueous solution (JTS K1408. No. 3 equivalent; Sing: 28% Na2O2 9%) was added at a rate of 1 per minute.
The mixture was supplied to a two-fluid nozzle at a flow rate of 0 g, and atomized into a container (volume fit: 30 f) under atmospheric pressure at a temperature of about 25° C. using carbon dioxide gas at a rate of 2 C/min as the atomizing gas.

The droplets and gelled product of the aqueous alkali metal silicate solution produced by the spraying were collected using a cyclone scrubber using carbonated water as a collection liquid.

The carbonated water containing the collected alkali metal silicate water 787 night droplets and gelled product was heated to a temperature of 30°C while stirring.
Spherical silica was produced by holding at °C for about 1 hour. The generated spherical silica was separated from the carbonated water and washed with pure water.

15 g of the obtained spherical silica was immersed in a 2N sulfuric acid aqueous solution (Li) and stirred at a temperature of about 100'C for about 1 hour to extract impurities, and then washed and filtered with pure water 5 times to obtain Nunoche. It was deoxidized and dehydrated to obtain hot warping power.

This heated silica was dried at a temperature of 150°C using a hot air dryer.
After drying for several hours, the obtained dried silica was placed in a quartz crucible and heated in an electric furnace at a temperature of 1250° C. for 2 hours to obtain spherical silica.

The obtained spherical silica has an average particle size of 20 μm and a specific surface area of 0.2rr! /g. As a result of microscopic observation, no air bubbles were observed within the particles.

The impurity content of this spherical silica is Na O, lppm
+At was 19 pm, and U was below O,tppb.

Comparative Example-1゜In the same manner as in Example-1, the sodium silicate aqueous solution was logged per minute.
The mixture was supplied to a two-fluid nozzle at a flow rate of 22 ml/min as the atomizing gas, and was atomized into a container at atmospheric pressure. Air at a temperature of approximately 150°C was supplied into the container at a rate of 30 ONf per minute, and sodium silicate water/8? & was dried to obtain spherical particles.

15 g of the obtained spherical particles were added to a 2N sulfuric acid aqueous solution II! The silica was immersed in the liquid and stirred for about 1 hour at a temperature of about 100°C to extract the inert substances twice. Obtained.

The resulting LR-shaped warping force had an average particle diameter of 20 IIm and a specific surface area of 0.3 nf/g. As a result of microscopic observation, air bubbles were observed within the particles.

The impurity content of this bH-type silica is Na 4 ppm
It was 20 ppm to 8 liters.

Claims (1)

[Claims] 1) A method for producing spherical silica, which comprises collecting droplets and/or gelled material produced by spraying an aqueous alkali metal silicate solution into an acidic gas, treating them with an acid-containing liquid, and then washing them with water.