JPS5935037A - Method for molding quartz glass - Google Patents

Abstract

PURPOSE:To facilitate the mold releasing of a molded quartz article and prevent the occurrence of cracks, by applying a carbon powder or graphite powder having a particle diameter within a specific range to the inner surface of a mold made of carbon or graphite for hot molding a lump of quartz at a high temperature. CONSTITUTION:A solid carbon or graphite, e.g. coke or charcoal, is pulverized and classified to prepare carbon powder or graphite powder having 0.01-10mum particle diameter, which is then dissolved in a volatile hydrocarbon, e.g. benzene, applied uniformly to the inner surface of a mold made of carbon or graphite in 0.01-0.05g/cm<2> thickness and dried. A lump of quartz is then introduced into the resultant mold and hot molded at >=1,700 deg.C temperature. The applied carbon or graphite powder is consumed by the reaction with SiO vapor, but the reaction of the SiO vapor with the carbon or graphite on the mold surface is eliminated to carry out easily the mold releasing of the molded article therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming quartz glass, particularly to an improvement in a method for hot-opening a quartz ingot in a mold.

Synthetic quartz, which is produced by thermal decomposition and hydrolysis reactions of natural quartz and silicon compounds, is obtained as a lump, so in order to commercialize it, it is remelted in an appropriate mold and molded. However, this mold has good heat resistance, thermal stability, and impact resistance, has poor reaction conditions with silica glass, and has good workability and is easy to manufacture. It has been proposed to use one made of carbon or graphite. However, even when thermal open molding is performed using a mold made of carbon or graphite, the quartz is fused to the surface of the mold, and the contact surface between the quartz and the mold may crack due to the difference in thermal contraction rate during cooling. Bragg may enter the quartz molded product, and in some cases, the mold may be destroyed. Therefore, when using a mold made of carbon or graphite, a method is exemplified in which soot, which is generated due to incomplete twisting of acetylene, is deposited on the inner surface of the mold. This soot is an aggregate of extremely small carbon particles and is porous, so when a quartz block is heated to 1700°C and JJ3 heated on top to form it, 1 quartz reacts with this soot layer S1.02 100 -+81
0 + 00t + io + 20 → 5i (j + c.

Therefore, the granular silicon carbide is consumed as L+7 silica and CO gas, but this granular silicon carbide forms the interface V between the quartz surface and the mold surface.
This scattering of moss prevents direct contact between the quartz and the mold surface, making it easy for the quartz molded product to peel off.As mentioned above, this soot is extremely fine and Since there are many spaces between particles, the actual thickness of the layer is extremely small compared to the apparent thickness. Therefore, in order for the silicon carbide particles generated at the interface between the 1-quartz surface and the @-type surface to have an effective exfoliation effect, this soot layer must be made considerably thick.
The apparent thickness must be 0 to 1 oooμ. However, when such a thick soot layer is applied, the soot layer often peels off during molding, and Bragg or chips are often observed on the quartz surface after molding due to fusion. Additionally, in this case, when silicon carbide is formed into a shape M, the soot layer aggregates and becomes granular. It reacts with the base material carbon or graphite to form silicon carbide, so if it is used again in its original state, the soot layer will peel off extremely easily and fusion will occur, causing the molded product to be considered defective. Therefore, in this case, it is necessary to scrape off the silicon carbide layer L7 on the mold surface in advance.

The present invention relates to a method for forming quartz glass that solves these disadvantages, and is a method for forming quartz glass with a particle size of 0.01.
~1077m carbon or graphite particles from 0.01 to 0.0
It is characterized by being coated to a thickness of 5 g/c/l and molded in a mold made of FC carbon or graphite at a temperature of 1700° C. or higher.

To explain this, 1. As a result of extensive research into the method of molding quartz glass by the present inventor - a method using a mold made of carbon or graphite.
If a carbon mask with a particle size of m is coated with graphite particles,
In this case, since the particle size is larger than that of acetylene soot, it will not aggregate, and even if it becomes silicon carbide by reaction with 810 vapor, the gaps between the particles will not become large. This SiO vapor no longer reacts with carbon or graphite on the mold surface,
As a result, it has been found that the quartz adult body can be easily released from the mold, and there is no problem when using this portal type repeatedly.

When applying these carbon or graphite particles, they are suspended in a continuous hydrocarbon thread bath medium and applied to the surface of the mold, and then the particles are applied to the gate-shaped surface by volatilizing the solvent. The present invention has been completed by confirming that it can be applied uniformly to a quartz molded product and that it can be easily released from a molded quartz product.

The mold used in the method of the present invention is, for example, JP-A-56-1
It is said to be a book with carbon or graphite legs disclosed in Japanese Patent No. 29621, but it is necessary that carbon or graphite particles with a particle size of 0.01 to 10 pm are coated on the surface by the method of the present invention. . It is preferable that the carbon or graphite particles are of high purity and contain almost no ash, and the particle size distribution can be adjusted by crushing solid carbon or graphite such as coke-charcoal. However, if it is too fine, its agglomeration will cause the disadvantages mentioned above, and if it is too large, it will have poor affinity with the mold base material and the coating will peel off from the mold surface. The particle size must be within the range of 0.01 to 10 pieces. In addition, if the amount of carbon 4 graphite particles applied to the mold surface is too small, the application to the mold surface tends to be uneven, resulting in uneven coating and 8 io when molding the quartz ingot. The steam is on the mold surface vc
There is a risk of penetration, and if there is too much of this, it will peel off from the mold surface and suffer the same disadvantages, so this is not recommended.
O.01-0.05g/cr117) range.

To apply these carbon or graphite particles to the mold surface, suspend them in a volatile hydrocarbon solvent VC, spray this, apply it to the mold surface with a brush, etc., and then apply the carbon or graphite particles to the mold surface. Preferably, this is done by Pi IJE, which evaporates the yarn solvent. Charcoal I in this suspension! ? The concentration of graphite particles may be 20 to 40% by weight, but it is preferable that the solvent has a boiling point of at least room temperature and is easily volatile. Therefore, this includes substances with a boiling point of about 80 to 150℃,
For example, benzene, an aromatic hydrocarbon (boiling point 80.1U)
),) Luene (1'10.6℃)-xylene (13
8 to 144°C), but it is also a chain chain or branched aliphatic hydrocarbon with a carbon number of 7 or more, such as normal butane (boiling point 98.4°C), normal octane (boiling point 125°C), .6
C) and normal nonane (150.7 C) can also be used.

In the method of the present invention, a quartz block is melted and molded in a mold made of carbon or graphite that has been surface-treated in this way.
The viscosity of quartz rapidly decreases at temperatures above 1,700°C, so it is necessary to perform this molding at a temperature of at least 1,700°C. However, if the temperature exceeds -1,900°C, the steam and sweat of Sin will increase. In addition to increasing processing loss, the reaction between this sio*i gas and the mold increases rapidly. Therefore, it is preferable to set the temperature in the range of 1730 to 1800°C. Note that this heat forming is usually performed at 10
'7. 1. Go to A2C in 180 minutes. However, in order to reduce raw material loss due to the evaporation of Sin in this song, a mold for the bracket, a heater to heat it, and a cut-off PI material 7j were used.
To reduce the consumption of K, it is preferred to carry out this in the presence of an inert gas such as helium or argon, or under a vacuum of, for example, less than 1 liter.

Furthermore, in the method of the present invention, the coating of carbon or graphite is carried out by the method described above, which has the advantage that it can be easily applied to molds with complex shapes. If the mold is to be used repeatedly, it is preferable to recoat the mold surface with carbon or graphite prior to use. This is because the carbon or graphite particles applied to the mold surface become silicon carbide during the formation and shaping of quartz, but most of them adhere to the surface of the quartz molded product and are removed. Therefore, in this case, the mold surface does not react with the slo steam to form silicon carbide, so there is no need to scrape or remove the silicon carbide from the mold surface force. Before reapplying the graphite particles, check the surface +
It is also good to rub ri+ with sandpaper or the like so that Q<M.

Next, examples of the present invention will be given.

Example 1 High-purity carbon particles with an average particle size of 0.6 μm were placed in a xylene solvent so that the lucidity ratio was 2 (l) on the inner surface of a square Pi-type made of high-purity carbon with a side of 125 m. When a suspension of carbon particles was applied and dried at 30°C, the carbon particles were
．． A mold coated with a thickness of 0.02 plry& (coating film height 200 μm) was obtained.

Next, a synthetic quartz rod-shaped body 100 m long and f 50 mm'7) was charged into this mold, and the temperature was raised to 1 soo'C in an Argox atmosphere and molded. The quartz molded product was released from the molded product extremely well, and no cracks were observed in this quartz molded product.

In addition, after smoothing the surface of this mold by rubbing it with sandpaper, carbon particles were again applied to this surface in the same manner as described above, and a quartz rod was formed from it. Similar results were obtained, which
The same thing happened after 10 repetitions.

Example 2゜ii The carbon particles in Example 1 were treated in the same manner as in Example 1, except that graphite particles with an average particle size of 9 μm were used. A mold having a graphite particle coating of 100 mL was obtained, and when this mold was used to mold the same quartz rod as in Example 1, similar results were obtained.

In this case, benzene,
Similar results were obtained using toluene, but
In terms of ease of coating, the order of ease of application was xylene, toluene, and benzene.

Comparative Example 1゜Carbon particles were applied to the mold surface using a xylene suspension of high-purity carbon particles as in Example 1 at a coating ratio of 20%. When this was used to form a quartz rod with a height of 120 μm, 10-times welding was observed, and the resulting quartz product exhibited a phenomenon of Bragg formation. .

In this case, the weight ratio of the xylene suspension is 20
This coating film 'ttO, 06g/i (coating film height 650
When a quartz rod was molded in the same manner using a mold with a diameter of 10 μm, countless fine bubbles were generated on the surface of the molded product.
The carbon layer also fell off, and the quartz molded product fused to the mold.

Comparative Example 2 Acetylene soot obtained from incomplete combustion in an acetylene burner was applied to the inner surface of the high-purity carbon mold used in Example 1 to a thickness of 6.
When a quartz rod was molded using this mold under the same conditions as in Example 1, it was successfully released into a quartz molded product. When a second molding was carried out using a mold to which acetylene soot was adhered, quartz molded 116 product 1-J was melt-printed to remove the carbon layer.

Therefore, we decided to use a diamond tool to scrape off the silicon carbide layer formed on the mold surface.

Each time this VC is used, it is necessary to remove the silicon carbide layer to a thickness of 500 to 1000 μm, which results in large dimensional errors in the mold, and furthermore, the surface becomes highly uneven. , the quartz molded product became defective.

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Claims (1)

[Claims] 1. A quartz block is heated at 1700°C in a carbon or graphite mold with carbon or graphite powder having a particle size of 0.01 to 10 fim coated on the inner surface to a thickness of 0.01 to 0.05117 cd.
A method for forming quartz glass characterized by forming at a temperature above or above. 2. Carbon or graphite powder with a particle size of 0.01 to 10 μm is suspended in a volatile hydrocarbon liquid, applied to the inner surface of a mold made of carbon or graphite, and dried. 11 A method for forming quartz glass described in JIIC.