JPS6186413A - Preparation of transparent siliceous sol exhibiting luster color - Google Patents

Abstract

PURPOSE:To prepare easily transparent and stable siliceous sol exhibiting luster color which has been obtd. difficultly by substituting alcoholic dispersing medium of conventional dispersion of amorphous silica sphere having uniform specified particle size in an alcoholic medium with a nonpolar solvent. CONSTITUTION:Amorphous silica spheres having uniform >=1 micron particle size are prepd. by such as hydrolysis of tetraethyl orthosilicate in ammoniacal alcohol, etc. An alcoholic dispersion of the silica spheres is prepd. and the alcoholic dispersing medium is substituted with a nonpolar solvent (e.g. benzene). Thus, a transparent and stable siliceous sol having luster color which has not been obtained conventionally is prepd. The siliceous sol is very stable being hardly influenced by atmospheric steam, CO2, and light. The sol is useful for the development of new materials in the field of plastic industry, paint, or optical material, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application The present invention relates to a method for producing a transparent and stable siliceous sol exhibiting a luminous color.

BACKGROUND ART Conventionally, there are almost no sol solutions that exhibit a luminous color and are stable.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for producing a transparent and stable siliceous sol that exhibits a luminous color.

By using this, it is possible to impart a luminous color to transparent plastics, and a new type of coating film can be obtained by using it as an additive for paints.

Structure of the Invention As a result of research on silica dispersions, the present inventor found that when dispersoids of silica spheres are dispersed in a solvent of a mixture of water and alcohol, the silica spheres float in the solvent with Brownian motion, producing a dark milky white color. exhibits. If the particles are allowed to stand still for several days in this state, gravity acts on each particle and they gradually gather at the bottom and settle without contacting each other due to the repulsive force caused by the charges acting between the particles. When this supernatant liquid is removed and alcohol is added and left to stand, an alcosol that is easily wetted by alcohol becomes an alcosol. The alcohol solvent of this alcosol is a nonpolar solvent such as benzene,
When substituted with toluene, xylene, tetralin, methylcyclohexane, etc., the non-polar solvent can maintain the electrical repulsive force between the silica spheres for a long time without depriving the silica spheres of charge, so all you have to do is shake them gently. The silica spheres float and return to the floating system, becoming a transparent stable sol with a luminous color. In hydrosils and alcosols, the dispersion agent contains polar molecules, so these remove the charge from the silica spheres.It was found that the silica spheres condensed and did not return to the original floating system even if shaken. Ta.

The present invention was completed based on this knowledge.

The gist of the present invention is to prepare an alcohol dispersion of amorphous bipolysilica spheres with a particle size of 1μ or less and substantially uniform particle size, and to prepare the alcohol dispersion medium with a nonpolar solvent. The present invention provides a method for producing a stable f5EiA siliceous sol exhibiting a luminous color characterized by the substitution of ", 1; "-"+".

In order to form a stable sol, the silica spheres used in the present invention must have a particle size of 1 μm or less and be amorphous and uniform in particle size. In order to exhibit luminous color (Tyndall diffused light), the particle size i: i 0 , 05-1
．． Preferably, it is 0μ. Methods for producing such fine particles of silica spheres with uniform particle size include, for example: (1) A method of hydrolyzing EkrJ ester (eg, tetraethyl orthosilicate) in ammoniacal alcohol.

(2) A method in which silicic acid is produced by treating sodium silicate with an ion exchange resin and then heated.

can be mentioned.

The supernatant liquid of the obtained silica sphere dispersion is removed, and the particles are washed by repeating the operation several times of gently injecting an alcohol such as 1,000 methanol, methanol, preferably ethanol, so as not to disturb the precipitate.

When this alcohol solvent is replaced with the above-mentioned nonpolar solvent, a transparent and stable siliceous sol exhibiting a luminescent color can be obtained.

The stability of this sol is extremely excellent, and even after it has been left standing in a closed container for several months, it can be restored to its original fluidity by stirring.

If allowed to stand still, each particle will gradually settle due to the action of gravity, increasing the particle density. However, as a result of the repulsive force caused by the same alt charge and the van der Waals attraction acting simultaneously between the particles, an extremely stable equilibrium state is maintained, so that the precipitate does not coagulate.

When the particle density reaches a certain degree, there is a tendency toward a close-packed arrangement and a face-centered cubic arrangement.

Since the spacing between the overlapping array surfaces is as small as the wavelength of the light, white light incident on the surface at a certain angle is split into spectra, and light of a specific wavelength is diffracted in a specific direction.

That is, a specific monochromatic light is seen, and by changing the position of the eye, its color changes continuously.

Example Example 1 or 1,000y 1° Ethyl alcohol 102d, ammonia water (concentration 28%
, 114m and 2 μm of distilled water, and a solution of tetraethyl silicate dissolved in 8 mAQ ethyl alcohol (34 volumes) were mixed. When this is slowly stirred, hydrosilicic acid is produced, and polymerization and condensation occur due to ammonia catalytic action.
Spherical silica was formed and the color became deep milky white. When this was allowed to stand for several days to several weeks, the silica spheres settled to the bottom of the vessel and the supernatant liquid became transparent.

Upper position a9. After repeating the operation several times of gently removing and injecting ethyl alcohol, the tube was left standing day and night. Ethyl alcohol was replaced with benzene, a nonpolar solvent, in the same manner as above. The white color of the precipitate disappeared and became almost colorless and transparent. The amount of benzene added determines the sol concentration. When this liquid is placed in a flask and vibrated, the precipitate becomes dispersed again and turns into a stable sol that is transparent with an opalescent tinge and exhibits a pale bluish-green or pale bluish-purple color. This sol was stable as long as the solvent did not volatilize, and no coagulation between particles occurred even after several months. The diameter of the dispersed silica sphere determined by observation using an 8-cell microscope was 0.28 μ, and the geometric standard deviation was 1.04.

Example 2゜Pure sodium silicate solution was mixed with cation-type ion exchange resin Amberly) IR120 (USA ROhm & H
Silicic acid was produced by passing it through a column packed with AAS (manufactured by AAS).

In order to prevent gelation, sodium hydroxide was added to the silicic acid to adjust the pH to 9.0 or higher, and the mixture was heated to 100°C to grow colloidal silica particles.

As water evaporates from the υ sol due to this heating, silica particles are grown by replenishing the amount with silicic acid sol while keeping the solution volume constant.

The average particle size of the produced particles depends on the heating time and the number of times new silicic acid sol is replenished, and the larger the number of particles, the larger the particles will grow. Particles having a particle size of about 0.2 to 0.4 μ can be easily produced.

Using these silica particles, a siliceous sol was prepared in the same manner as in Example 1 using benzene as a dispersion solvent. The results were similar to those in Example 1.

4. Effects of the Invention According to the method of the present invention, it is possible to easily produce a transparent and stable siliceous sol exhibiting a luminous color that has been difficult to obtain in the past.

In addition, the obtained siliceous sol has excellent properties such as being extremely stable and hardly affected by water vapor, carbon dioxide gas, light, etc. in the atmosphere.

Therefore, it is conceivable that this can be used to develop new products for the plastic industry, paints, optical materials, etc.

Claims (1)

[Claims] (1) A luminous coloring method characterized by preparing an alcoholic dispersion of amorphous silica spheres with a particle size of 1μ or less and having substantially uniform particle sizes, and replacing the alcoholic dispersion medium with a nonpolar solvent. A method for producing a transparent and stable siliceous sol.