JPS6065735A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To obtain quartz glass having improved heat resistance at a low cost, by using fine powdery silica having a specific particle diameter in the sol-gel method using an alkyl silicate and the fine powdery silica as main raw materials. CONSTITUTION:Aqueous hydrochloric acid is added to hydrolyze an alkyl silicate, e.g. ethyl silicate, under vigorous agitation, and fine powdery silica having >=300Angstrom average particle diameter is added to the resultant solution, uniformly dispersed and adjusted to 4-6pH to form a sol solution. The resultant sol solution is then contained in a suitable container, gelatinized, contracted and dried to give a dry gel, which is further sintered to afford the aimed quartz glass.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing quartz glass, and more particularly, a method for producing quartz glass at low temperatures by a sol-gel method using alkyl silicate and finely powdered silica as main raw materials. A relatively large finely powdered silica with an average particle size of 30OA or more is used as a raw material, and this and alkyl silicate,
This invention relates to a method for producing transparent homogeneous quartz glass by mixing water and hydrochloric acid to produce silica gel and then sintering the keratin.

First, I will touch on the usefulness of quartz glass. In recent years, quartz glass has been developed with a concentration of impurities such as copper and boron of 0. l
As high-purity products of less than ppm can now be manufactured, they are now widely used in crucibles and boards in the manufacturing process of germanium, silicon, and other semiconductors, as well as in the core tubes of diffusion furnaces, as well as in beakers for physical and chemical use. , which are often used as cells for optical measurements, and high-quality cells with low hydroxyl content and excellent optical uniformity have been developed and are used for various optical applications, especially quartz for optical communication. Glass fiber is attracting attention. Quartz glass, which has such a wide range of uses, is currently manufactured generally by the following three methods.

Ill How to clean natural crystal and melt ξ [2]
SHO using high purity EiCi4 or sgr4 as raw material
Method for making wealth 131 Method of melting natural silica sand (Produces quartz glass containing bubbles) However, with any of the above manufacturing methods, raw materials are expensive and processing at high temperatures is required. For a number of reasons, quartz glass is extremely expensive.

Therefore, as an inexpensive method for producing quartz glass, a method for producing quartz glass at low temperatures using a sol-gel method has recently been attracting particular attention. This method is briefly explained as follows:
PurposeThis sol-gel method involves preparing a sol using a metal alkoxide containing a glass component as a raw material, gelling it by heat treatment, drying (accompanied by shrinkage), sintering, and vitrifying it. The characteristics of the quartz glass manufacturing method according to the method are as follows:+11 It is energy saving because it can be manufactured at a lower temperature than when manufacturing by a high temperature melting method using quartz as a raw material.

(2) High purity glass can be obtained because the raw materials are easy to purify.

(31 A homogeneous glass is obtained for use as a low viscosity solution ti material.

Because of these many advantages, research into the production of silica glass using this method is being widely conducted in various places.

However, according to the materials published so far, there are many unresolved problems and the technology has not yet been put into practical use.

The following method has been devised as one of such sol-gel methods. i.e., a suitable alkyl silicate) 5
j(oR)4 (R is an alkyl group having 1 to 10 carbon atoms), a suitable alcohol solution (containing water), hydrochloric acid, and finely powdered silica are mixed and dispersed to form a silica sol, and the pH value is adjusted with aqueous ammonia, etc. , heat treatment, etc. to form silica gel. The obtained bulk silica gel is placed in a furnace and sintered according to a predetermined program to form quartz glass.

The greatest advantage of this method is that plate-shaped quartz glass with a large p1 can be easily obtained by adding finely powdered silica. However, even when finely powdered silica is added, cracks occur during dry gel preparation, foaming, and devitrification occur during sintering.
In addition, foaming may occur during post-sintering heat treatment (approximately 1250°C) when fine powder silica with an average particle diameter of less than 300A is used, making it impossible to obtain the desired large plate-shaped silica glass. The purpose of this is to solve the above problems by limiting the average particle diameter of the raw material fine powder silica, that is, as the raw material fine powder silica,
A material with an average particle size of aoo
Diguaaa Inc.). Prepare a hydrolyzed solution by mixing Rima 9, ethyl silicate, water, alcohol (with or without), and hydrochloric acid, and add fine powder silica (eg, trade name) with an average particle size of 3008 or more to this solution.
ILo x 50 (Dig1bsaα) @ *
-40OA, N1psi E, 150K, Ei
1505, JI1200, Fi200A,
3220, B220A (K to Nippon Silkani Industry)
, 1000-4500X, etc.), and add operations such as ultrasonic dispersion, centrifugation, and filtration to improve dispersibility. After this, adjust the full H value to a high value with aqueous ammonia, etc. This makes it possible to shorten the gelation time. This is transferred to a container, gelled, and dried, and the resulting dry gel is placed in a furnace and sintered. If you use this method, there will be as little chance of cracking as possible during drying.
The yield rate is significantly improved, and post-sintering heat treatment (130
0° C. for 3 hours), no phenomena such as foaming or devitrification occurred. However, if the particle size exceeds zooooX t, the sintering temperature will be very high9, but it is preferable to prepare glass at low temperatures, which is an advantage of the sol-gel method.
Finely powdered silica with a particle size of about 5008, i.e. (trade name) Anasko LOX so (Dirtα88α)
It is best to use

Hereinafter, the content of the present invention will be explained in more detail according to Examples.

Example Commercially available noethyl silicate (8i (OBt)4) 264
? ? J and 0.0IN HCA 21677L#1! :
The mixture was mixed and stirred vigorously to carry out a hydrolysis reaction. After hydrolysis is complete, continue stirring and add 90 g of silica powder to this solution.
was added gradually.

After addition, in order to improve dispersibility, stirring was carried out for 2 hours, ultrasonic dispersion was carried out for 3 hours, and centrifugation was performed at 3000 rpm.
, prn, for 10 minutes) After that, ammonia water was added dropwise to adjust the pH value to 4.5-5. Adjust OK and filter (400mg
After 5 hours (D polypropylene sheet), 27 x 2
The mixture was transferred to a 2 cm polypropylene container, covered with a lid, and allowed to gel at room temperature. The above is the operation method for one container, but in this experiment, we used ■AEROS Engineering LOX 50 (400”) *■ as fine powder silica.
Hipail E220A (1000 back), ■N1ps
il R200 (2500X),, ■Cob-a-
For each of the four types of ai1M-5 (100A), 40 containers were tested, and the drying conditions were set to 4 as described below.
I changed it to snails and dried it. After gelation, when shrinkage began, the lid was replaced with a perforated lid with adjustable drying rate. Here, the open area ratio of this lid is +1) 1.0 factor, 12
12.0%, 1315.0%, (4) 1000%
Using 4 types [10 sheets each], put them in a dryer and raise the temperature from (capital) °C to ω °C at a heating rate of 3Vnr.
Thereafter, the temperature was maintained at ω°C (5) and dried. This result is shown in Table I
In this way, the yield rate is greatly affected by the drying conditions, but when using the above ■~■, the open area ratio is 1
It has become clear that when the content is set at ~2%, a dry gel can be produced without cracking. However, regarding ■, there was almost no improvement. The size of the dried gel obtained here has almost no relation to the type of finely powdered silica;
゜5×14. The gel in the plate-shaped container with a large p1 porosity with OX O,6 side was warped. This dried gel was heated and sintered at a heating rate of 180 Vnr. Further, after sintering, heat treatment was performed at 1300° C. for 3 hours. These results are shown in Table 2. The larger the particle size of the finely powdered silica added, the higher the sintering temperature.There was no problem in heat treatment for items 1 to 2, but item 2 foamed and swelled to a white color. Moreover, the size of each sintered body when sintered is i4. OX9.8X0.4crn, and the results of physical property analysis are Vickers hardness 800Kl/
-u-" - specific gravity 2.2, infrared absorption spectrum,
The near-infrared absorption spectrum and refractive index completely matched those of fused silica glass. However, regarding ■, the amount of OH was somewhat large. This is thought to be the cause of foaming and devitrification during heat treatment.

In addition to the previous example, similar experiments were conducted using a slightly smaller container or a circular container (Petri dish), and similar results were obtained. In addition to the above, particle diameters include 50A, 200A, 600A, and 40A.
00H fine powder silica was used, but 50A and 2ooX
The results could be roughly divided into three types: ■, 600X, and ■■, 4000K.

As shown in the examples above, the yield pb, sintering temperature, and heat resistance of quartz glass are greatly affected by the particle size of the finely powdered silica to be added. Therefore, in order to manufacture quartz glass with excellent heat resistance at a lower cost, it is preferable to use fine powder silica with an average particle size of 30 OA or more.
OX 50 (product name) is the best choice from ARROS.

The quartz glass thus produced according to the present invention is
Due to its major advantages such as lower cost than conventional methods (melting method), silica glass with good heat resistance can be manufactured easily in fields where quartz glass has been used up until now. Therefore, it is thought that its application will expand to a wider range of applications, such as optical applications.

[Brief explanation of drawings]

Table 1 shows the yield of dried gel after gelling performed in the example, and Table 2 shows the results of sintering and heat treatment (1300°C, 3 hours) of the obtained dry gel. The results are summarized for each type of fine powder silica (with different particle sizes) used.

Claims (1)

[Claims] A method for producing quartz glass, characterized in that a sol-gel method using alkyl silicate and finely powdered silica as main raw materials uses finely powdered silica having an average particle size of 300X or more as a raw material.