JPS62207723A - Production of glass - Google Patents

Abstract

PURPOSE:To facilitate mass production of glass basing on sol-gel method by hydrolyzing alkyl silicate with a basic catalyst, then concentrating obtd. dispersion of fine silica particles by using ultrafiltration and vacuum distillation in combination. CONSTITUTION:Alkyl silicate such as Si(OEt)4, etc., is hydrolyzed with a basic catalyst such as ammonia, etc. Solvents alone in the obtd. dispersion of fine silica particles other than the effective components such as water, alcohol, etc., are separated effectively using ultrafiltration membrane permitting bulk production. Then, the above described liquid dispersion is subjected to vacuum distillation, and reaction catalyst having adsorbed to fine silica particles are isolated and removed easily and completely. Solution of the hydrolyzate is added to the obtd. stable concentrated liquid of fine silica particles, and final sol is formed by stirring and mixing the mixture. After gelling and drying the above-described sol, the gelled product is sintered by heating to obtain quartz glass having high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing glass by a sol-gel method.

[Summary of the invention]

The present invention is a method for producing glass by the sol-kel method, in which a silica fine particle dispersion obtained by hydrolyzing an alkyl silicate with a basic catalyst is concentrated using a combination of an ultrafiltration membrane and vacuum distillation. This makes the process of condensing the dispersion liquid efficient and smooth, and facilitates mass production.

[Prior art] Conventional sol using alkyl silicate as the main raw material
In glass production by the Glue method, the silica fine particle dispersion obtained by hydrolyzing an alkyl silicate with a basic catalyst is concentrated by vacuum distillation or ultrafiltration.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, in the case of vacuum distillation, the concentration rate is slow and it takes a long time to reach the desired concentration rate.
Stability as a dispersion may be lost, viscosity may increase, particles may aggregate, and it may be difficult to proceed to the next step. Another problem is that it is difficult to completely recover the t-solvent (because some amount is drawn into the vacuum line), and concentration accuracy is lacking. Further, in the case of ultrafiltration, there is a problem that the reaction catalyst adsorbed on the silica fine particles is hardly released, and the particles may aggregate in the next step.

Therefore, the present invention aims to solve these problems.
Its purpose is mass production.

The sol-gel method allows the process to proceed smoothly by performing concentration using a combination of ultrafiltration, which is advantageous, and vacuum distillation, which is effective against the release of reaction catalysts adsorbed on silica particles, which is a problem with ultrafiltration. The purpose of the present invention is to provide a method for manufacturing glass.

[Means for solving problems]

The method of the present invention involves a combination of ultrafiltration and vacuum distillation of a silica fine particle dispersion obtained by hydrolyzing alkyl silicate with a basic catalyst in the production of glass by the sol-gel method using alkyl silicate as the main raw material. A method for producing glass characterized by concentrating it.

[Function] According to the present invention, it is possible to separate at the molecular level using an ultrafiltration membrane, which is an advantage of ultrafiltration. In addition, it is possible to increase the concentration rate by adjusting the flow rate, making it easy to mass-produce.The advantage of vacuum distillation is that heating and reducing the pressure can reduce the amount of reaction catalyst adsorbed on silica particles. This is a concentration method that has two features: it facilitates the release of the dispersion and maintains the stability of the dispersion in the next step, making it easier to make the process smoother.

〔Example〕

1) Purified commercially available ethyl silicate (Si(OEt)
4) 44,11, ethyl alcohol 67.2 l,
Water 15.6 and ammonia water (29%) t 2
1 was charged into a reactor and stirred at 800 rpm for 25 hours. Fine silica particles were generated in about 10 minutes after stirring started, and the mixture became cloudy, and after 5 hours, it became completely opaque and white.

Thereafter, the mixture was allowed to stand for 5 days at a temperature of 20 to 50C to grow fine silica particles. Two other batches of dispersions of silica fine particles similar to this were prepared. The average particle diameter of the silica fine particles at this time was measured using a centrifugal sedimentation type particle size distribution analyzer and was found to be α25 μm.

21.6 liters of water was added to each dispersion of silica fine particles prepared as above while stirring, and after the addition (stirred for L5 hours), subsequent concentration was carried out by three methods (■ to ■). , The example shown here is a case where a problem occurs with regard to (1) and (2).

■ Silica fine particle dispersion I'lk is divided into two equal parts of approximately 751 pieces,
In order to increase the concentration of silica fine particles after concentration by vacuum distillation in two 10Ol distillation plants to 55 wt% or more,
It took 15 to 20 hours to concentrate 6 to 7 times, or 60 to 651 in separated liquid volume.

At this time, a large amount of dry pieces adhered to the interface between the dispersion liquid and the container, resulting in loss of effective silica fine particles.

■ Using an ultrafiltration system (membrane area: 10@), dispersion liquid inflow pressure is 5 kl? Perform circulation concentration at / cm, ■
It took 1.5 to 2.0 hours to reach a concentration equal to . At this time, since the test was carried out in a closed state, there was almost no loss of silica due to dry pieces.

■ Using an ultrafiltration system (membrane area: 1.07 FL), the dispersion liquid inflow pressure was set to 5 to 9/at? When the filtrate amount reached 1101, it was transferred to the 1001 distillation plant, and vacuum distillation was performed to obtain the same concentration ratio as ① and ②. The time required at this time was 1.0 hour for ultrafiltration and 3 hours for vacuum distillation. At this time, some dried pieces of silica were attached to the interface between the dispersion liquid and the container.

While stirring, 2HHCl was added dropwise to the silica fine particle dispersion prepared as described above in steps 1 to 2 to adjust the PR value to about 4.7. This is done in order to prevent kelization due to progress of dehydration polycondensation of silanol when mixed with a hydrolyzed solution of ethyl silicate in the subsequent step, and to maintain the stability of the mixed solution. In this process, ■ and ■ could be treated without any particular problems, but for ■, the pH value was 7.
．． When the temperature decreased to around 0, the particles rapidly agglomerated and solidified, making further processing impossible.

Next, a hydrolyzed solution of ethyl silicate was prepared. When mixing the silica fine particle dispersion, purified ethyl silicate 1a91 and 0.02 NHc16.151, which act as a binder between particles, were mixed and vigorously stirred. Since the amount of heat generated during the reaction was large, the mixture was stirred while being cooled, and the reaction progressed until it became transparent and homogeneous within 1 hour.

Two batches of this were prepared for mixing (1) and (2) above.

The silica fine particle dispersion prepared as described above and the hydrolysis solution were mixed with stirring to form a final sol. At this time, the pH value of the sol was around 4.5. After each sol is subjected to treatments such as centrifugation and filtration as necessary, qoamt of 50 x 30 x 10 c! ! After pouring into 50 L polypropylene containers and gelling in a sealed state, when the wet gel has shrunk to a certain extent,
A lid with an adjustable drying rate was placed on the product, the product was placed in a dryer, and the temperature was raised from room temperature to 60 to 80°C at a rate of 5°C/hr, and the temperature was maintained at this temperature until drying was completed in 1.2 to 3 weeks. The size of the dried gel obtained here is 198 x 198 x 6.5n when using the dispersion concentrated by the method (■), and 209 x 209 x 7 when using the dispersion concentrated by the method (■).
zg, and it was estimated that when the concentration method (2) was used, the loss of silica fine particles would be quite large. The yield of the former is 6aO%.

The latter was 80.0%, and the result was that the latter was better because of its smaller shrinkage rate.

The dried shell thus obtained was placed in a sintering furnace and heated and sintered using a predetermined temperature increase program to obtain a transparent glass body at 1260°C. The size and weight of this glass body are 1! +7x157x4.5 pieces, 200t, the latter is 144x144x4.8B, 220? Met. The results of physical property analysis of the glass thus produced were consistent with those of fused silica glass, including Vickers hardness, specific gravity, thermal expansion coefficient, infrared absorption spectrum, near-infrared absorption spectrum, and refractive index. Also, no impurities were detected in the pure summer analysis. In addition, 160% of the glass produced here
By applying high temperature treatment at 0° C. or higher, a very high quality quartz glass with no internal defects was obtained.

〔Effect of the invention〕

In this way, the glass produced according to the invention can be concentrated by vacuum distillation and remaining in the dispersion after concentration, which in the prior art was time consuming, inefficient and resulted in loss of active ingredients. Ultrafiltration, where it was difficult to maintain stability in the post-process due to the reaction catalyst, is compensated for by using both of these in combination, and the process of concentrating the silica fine particle dispersion can be carried out efficiently and efficiently. , it becomes easier to respond to mass production.

In addition, the quartz glass produced by the present invention is lower in cost than other quartz glass production methods (such as the melting method),
Since the raw materials are all liquid, they can be purified, making it easy to mass-produce high-quality quartz glass.

Therefore, it is thought that it will be applied not only to fields where quartz glass has been used up until now, but also to various fields such as photomask substrates for ICs and base materials for optical fibers. Furthermore, A I , T i , G e HN a+C
By adding various elements such as a, Mg, Li, and Te at the time of sol preparation, it is easy to produce high-quality multicomponent glasses with various properties.

that's all

Claims (1)

[Claims] (1) In the production of glass by the sol-gel method using alkyl silicate and ultrafine silica as main raw materials, the silica fine particle dispersion obtained by hydrolyzing the alkyl silicate with a basic catalyst is passed through an ultrafiltration membrane and vacuum distillation. A method for producing glass characterized by concentrating it in combination with.