JPS643812B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves the production of quartz glass by separately hydrolyzing alkoxysilane using acidic and basic catalysts, mixing well, gelling at pH 3 to 6, drying and sintering. Regarding the law.

A non-melting glass manufacturing method in which a dry gel obtained by hydrolyzing a metal alkoxide and gelling it is heated is called a sol-gel method. Using metal alkoxides as starting materials has attracted attention because homogeneous glass can be produced at relatively low temperatures even with compositions that are difficult to produce by melting methods. However, it generally has the disadvantage that it tends to break during the gelling shrinkage process after hydrolysis or during heating of the dried gel.

Although quartz glass is a frequently used and useful material, it is currently manufactured by melting it at around 2000°C, making it extremely expensive. The sol-gel method has features such as high purity, low cost, and energy savings, but it has not been able to produce large-sized quartz glass.

In order to prevent fracture during the sintering process, it is necessary to prepare a dry gel containing a large amount of relatively large pores of 50 to 80 Å. When a base such as ammonia is used as a catalyst, the dried gel produced contains a large number of pores larger than 50 Å, so there are no cracks during sintering. However, it is extremely difficult to produce a dried gel in the desired shape, and no examples have been published in which a dried gel with a diameter of 2 cm or more has been obtained.

In order to overcome this drawback, it is effective to mix a sol hydrolyzed with a base with a sol hydrolyzed with an acid to form a gel.

Although dry gels using mixed sol are much easier to produce than those using only base catalysts, the yield is still low from a practical standpoint. In particular, when the mixing ratio of the sol hydrolyzed with a base catalyst is increased,
If the silica particle size in the sol is increased, it becomes difficult to obtain a dry gel. On the other hand, if the mixing ratio of the sol hydrolyzed in an acidic state is increased or the silica particle size in the sol catalyzed by a base is decreased, a dry gel can be produced at a high rate. However, since it does not contain many pores larger than 50 Å, it becomes easily cracked during the sintering process.

In order to produce large quartz glass at a high rate,
A dry gel containing a large amount of fine silica particles with a relatively large particle size must be produced in high yield.

The object of the present invention is to solve the above-mentioned problems and to provide a large, bubble-free glass at a low cost, which is no different from conventional quartz glass.

The method for producing quartz glass of the present invention includes uniformly mixing a sol obtained by hydrolyzing alkoxysilane using a base as a catalyst and a sol obtained by hydrolyzing using an acid as a catalyst to form a gel, and then drying. A method for manufacturing silica glass by sintering is characterized in that a uniformly mixed sol is adjusted to have a pH in the range of 3 to 6 and then gelled. In other words, a sol in which fine silica particles with a relatively large particle size are dispersed by hydrolysis using a base as a catalyst, and a sol in which tetrahydroxysilane formed into dimers and tetramers by hydrolysis using an acid as a catalyst. By uniformly mixing the two, adjusting the pH to 3 to 6, and then gelling, it is possible to stably produce large-sized quartz glass.

When an acid is used as a catalyst, the hydrolysis rate is fast and the polymerization rate is slow, so grain growth does not occur. It is thought that polymerization proceeds in a network-like manner, the bonding force is strong, and dry gels are relatively easy to prepare. However, differences in polymerization rate occur depending on the drying conditions, and if this cannot be controlled, cracks will occur.

When a base is added to a sol that has been hydrolyzed with an acid to bring it closer to neutrality, the polymerization rate is significantly accelerated and gelation and shrinkage occur instantaneously. Therefore, the difference in drying conditions is
It does not affect the polymerization rate unless it is very extreme,
It will not cause cracks. By leaving the sol adjusted to pH 5 open at room temperature, a dry gel could be produced without cracking.

By chemically adjusting the hydrogen ion concentration, the polymerization reaction proceeds uniformly, quickly, and with the formation of a strong network structure, making dry gel production extremely easy. A suitable pH range is 3 to 6.

If the pH is below 3, the polymerization rate will be slow and the effect will be weak.
If the pH is 6 or higher, the polymerization rate is too fast to be controlled.

By utilizing this feature of the present invention, a dry gel containing a large amount of silica fine particles having a relatively large particle size could be produced at a high yield.

Hereinafter, the present invention will be explained in detail based on experimental examples.

Experimental example 1 (Si(OC ₂ H ₅ ) ₄ :H ₂ O:C ₂ H ₅ OH)=(1:10:
They were mixed at a molar ratio of 8) to form a homogeneous solution. The water is
Using a 0.1N ammonia aqueous solution, the tube was sealed tightly and left at room temperature for 3 days to allow hydrolysis and grain growth. The silica particles had grown to nearly 0.1 μm. The white translucent sol was concentrated to a silica concentration of 25 wt% using a rotary evaporator.

Meanwhile, stirring was continued for 1 hour under ice cooling at a molar ratio of (Si(OC ₂ H ₅ ) ₄ :H ₂ O)=(1:10). A 0.1N aqueous hydrochloric acid solution was used as water to obtain a colorless and transparent homogeneous solution. This mixed sol, which was also concentrated to a silica concentration of 25 wt% and thoroughly mixed with a sol prepared using an ammonia catalyst at a volume ratio of 1:1, exhibited a pH of 3. This is probably because ammonia was removed during the concentration process.

While stirring, 0.1N ammonia water was gradually added dropwise to the mixed sol to adjust the pH to 4.6. The mixture was poured into a polytetrafluoroethylene container with a diameter of 10 cm and a height of 5 cm, and gelled after 30 minutes when left at room temperature. It was covered with a lid with 20 holes of 3 mm in diameter, kept at 60°C for 1 day, and then gradually raised to 90°C. After drying at 90°C for 2 days, a dried gel with a diameter of 6 cm was obtained.

When the pore size distribution was measured, it contained a large amount of pores of 40 to 80 Å, and even when sintered at a rapid temperature increase rate of 5°C/min, it did not crack at all, and vitrified at 1150°C, becoming colorless and transparent. We were able to produce quartz glass with a diameter of 4.5cm.

Experimental Example 2 A mixed sol adjusted to pH 4.6 in the same manner as in Example 1 was gelled in a polytetrafluoroethylene container with a diameter of 20 cm and a height of 10 cm, and 20 holes with a diameter of 6 mm were made.
I opened it and put the lid on. After drying at 60°C for 2 days and 90°C for 3 days, a dried gel with a diameter of 12 cm was prepared.
It was sintered at 1150°C to obtain quartz glass with a diameter of 9 cm.

Experimental Example 3 A sol that was separately hydrolyzed and concentrated in the same manner as in Experimental Example 1 was converted into (ammonia catalyst: hydrochloric acid catalyst) =
They were mixed uniformly at a volume ratio of (2:1). After adjusting the pH to 4.6, it was transferred to a container with a diameter of 10 cm, and a dried gel with a diameter of 6 cm was obtained by the same drying process.

When heated to 1200℃, it becomes vitrified and the diameter
We were able to manufacture 4.5cm quartz glass.

Experimental example 4 (Si(OC ₂ H ₅ ): H ₂ O: C ₂ H ₅ OH) = (1:5:
They were mixed at a molar ratio of 5) to form a homogeneous solution. The water is
Using a 0.1N ammonia aqueous solution, the tube was sealed tightly and left at room temperature for 3 days to allow hydrolysis and grain growth. The silica particles had grown to a size of nearly 1 μm. White opaque sol with silica concentration up to 25wt%,
Concentrate using a rotary evaporator.

Meanwhile, stirring was continued for 1 hour under ice cooling at a molar ratio of (Si(OC ₂ H ₅ ) ₄ :H ₂ O)=(1:10). A 0.1N aqueous hydrochloric acid solution was used as water to obtain a colorless and transparent homogeneous solution. It was also concentrated to a silica concentration of 25 wt% and mixed well with a sol prepared using an ammonia catalyst at a volume ratio of 1:1.

A dried gel with a diameter of 6 cm was prepared using the same drying method as in Experimental Example 1.

When heated to 1300℃, it becomes vitrified and the diameter
We were able to manufacture 4.5cm quartz glass.

As described above, according to the present invention, by mixing two types of sol solutions, that is, a sol solution hydrolyzed with an acidic catalyst and a sol hydrolyzed with a basic catalyst, (1) fine particles (sol) are generated. The comrades form a strongly bonded skeleton, and are used in the shrinkage process caused by gelation, the drying process to remove evaporated components such as solvents to form a dry gel, and even the sintering process to form quartz glass. , it is possible to produce large-sized quartz glass that does not break at all.

(2) Since all raw materials are alkoxysilanes, it can be purified and highly pure quartz glass can be obtained.

(3) Since all the raw materials are liquid during manufacturing, it is easy to handle, there is no need to worry about dust or the like in terms of health and safety, and it is possible to provide inexpensive quartz glass that consumes very little energy.

For these reasons, it has a wide range of uses, including physical and chemical equipment that requires high-purity, large-sized quartz glass, photomasks for IC manufacturing, IC boards, and IC substrates.

Claims (1)

[Claims] 1 A sol obtained by hydrolyzing alkoxysilane using a base as a catalyst and a sol obtained by hydrolyzing using an acid as a catalyst are uniformly mixed to form a gel, and then dried and
A method for producing quartz glass by sintering, which comprises adjusting a uniformly mixed sol to have a pH in the range of 3 to 6 and then gelling it.