WO1990000637A1

WO1990000637A1 - Process for producing artificial rock crystal

Info

Publication number: WO1990000637A1
Application number: PCT/JP1989/000671
Authority: WO
Inventors: Koichi Orii; Iwao Oshima; Mutsuo Owaku; Kiyoshi Sunaoka
Original assignee: Nitto Chemical Industry Co., Ltd.; Mitsubishi Rayon Co., Ltd.
Priority date: 1988-07-06
Filing date: 1989-07-05
Publication date: 1990-01-25
Also published as: JPH0218393A

Abstract

The invention relates to a process for producing artificial rock crystal by hydrothermal growth starting with crystalline silica obtained by heating amorphous silica. This process provides a highly pure artificial rock crystal containing only minute amounts of impurities (particularly Al).

Description

Description Manufacturing method of artificial quartz [Technical field]

The present invention relates to a method for producing an artificial quartz. More specifically, the present invention relates to a method for producing an artificial quartz having a low impurity (particularly, A) content. [Background Technology]

Natural quartz has been used as an oscillator material for a long time. However, due to the stability of quality, natural quartz has been replaced by artificial quartz, and at present it is a material for applications requiring special ultra-high quality. Except for the above, artificial quartz is used in almost all applications. Artificial quartz is physically and chemically stable, has excellent mechanical properties, and has a high degree of stability in vibration frequency. No substitute material has been found for vibrators. Artificial quartz is not only a resonator, but also optical devices such as sapar plates, wave plates, and double image prisms, filters such as VHF band filters, phase linear filters, and elasticity. It is widely used as an electronics material for surface wave devices.

However, as satellite communication has become popular in recent years, frequency fluctuations caused by the effects of radiation in outer space have become a problem, and measures to prevent it have become an important issue. Has become. This phenomenon is thought to be mainly due to impurities in the crystal (especially A J2).

The hydrothermal growth method as a method for producing artificial quartz is described, for example, in the Ceramic Society of Japan: 1 L [4] 1969, -111 to 118. From crystalline materials that are insoluble or very poorly soluble at room temperature, 髙 ♦ a high concentration aqueous solution containing a suitable mineralizer is prepared under high pressure, and the seed crystal is made using the difference in solubility depending on the temperature. The above-mentioned operation of promoting crystal growth is called hydrothermal growth of the crystal. When growing a crystal, a temperature difference is set up and down in an aqueous solution of high temperature and pressure, and the crystalline material as a raw material is dissolved on the high temperature side (lower), and on the low temperature side (upper). _D water ripening temperature gradient method of growing a crystal of a solute is deposited on the seed crystal is used

As raw materials for the production of artificial quartz, conventionally, scrap quartz and lasca have been used.

It is conceivable to use natural quartz with few impurities to meet the demand for pure products, but since high quality natural quartz itself is dying, it is not only expensive but also difficult to obtain. .

Therefore, there is a strong demand for the development of a method for obtaining high-quality artificial quartz in place of high-quality natural quartz.

However, conventionally, quartz used as a raw material for growing artificial quartz is a single crystal, and it is difficult to remove impurities derived from the raw material in advance. It is notable that post-treatment removes impurities that have been incorporated. Have difficulty .

Conventional natural quartz usually contains Ί · ρ of 以上 0 ρ ρπι or more. Is an element that is difficult to remove, and it is difficult to remove it by means such as heat treatment and acid extraction.

The artificial quartz obtained by the growth is of good quality, with few structural defects in the crystal, impurities, or foreign matter.

Therefore, the production of artificial quartz using synthetic silica having a low content of impurities (especially Α · β) as a raw material is advantageous for obtaining high-purity artificial water crystals.

[DISCLOSURE OF THE INVENTION]

An object of the present invention is to provide a method for producing an artificial quartz having an extremely low content of impurities (particularly).

The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, it has been found that mature pure silica is ripened in the presence or absence of an alkali metal. As a result, the crystallization of the amorphous silica is promoted, and the artificial quartz can be manufactured by hydrothermal growth using the crystallized silica as a raw material. I found out.

That is, in the production of artificial quartz by hydrothermal growth, the present invention uses a crystalline silica obtained by heating an amorphous silica as a raw material. A method for producing an artificial quartz comprising: According to the method of the present invention, it is possible to obtain a high-quality artificial quartz having a very low content of impurities (particularly Α · δ), a high purity, and no influence from radiation.

[Best mode for carrying out the invention] Hereinafter, the present invention will be described in detail.

It is preferable that the amount of impurities in the amorphous silica used as a raw material in the method of the present invention is as small as possible.

Alkali metals such as L i, N a, etc., and alkaline earth metals such as M g, G a, A i, T i _r C r, as impurities in the amorphous silica It is desirable that the content of transition metals such as Fe.Gu be 10 ppra or less. In particular, it is desirable that the A ^ content be 5 ppm or less, preferably 3 ppm or less, and more preferably 1 ppm or less.

The production method of the amorphous silica is not limited as long as it has few impurities. It may be obtained by any method such as alkali silicate, silicon tetrachloride, and alkoxy silane. For example, the inventors of the present invention have previously proposed Japanese Patent Application Laid-Open Nos. Sho 62-30111, Sho 62-31012, and Sho 62-28 38 09 The amorphous silica used in the method of the present invention can be obtained by the methods described in Japanese Patent Application Laid-Open No. 62-2838010.

That is, amorphous Shitsushi Li Ca has a viscosity in the range of 2 5 0 〇 Boise, general formula: It's _{M 2 0 * n S i 0} 2 ( other, M is table the alkali metal, n represents S i 0 ₂ moles

Aqueous solution of an alkali silicate represented by the formula (1), through a spinning nozzle having a pore size of 1 mm or less, a water-soluble organic solvent or 4 N or less. The mixture is extruded into a coagulation bath composed of an acid solution of the above to coagulate into a fiber form, and the obtained fiber gel is treated with a liquid containing an acid, and then washed with water to extract impurities. It can be obtained by removal by extraction.

Further, even if the silica obtained in this way is further heated at a temperature of 10〇0 or more, as long as the silica is amorphous, It can be used as a raw material for the above method.

According to the above method, the content of radioactive substances such as alkali metal elements, chlorine, and lanthanum, and the content of various impurities such as (Ki, Fe, etc.) is 1 ppm or less. In addition, it is possible to obtain a high-purity amorphous silica having an arbitrary specific surface area.

Regarding the amorphous silica used in the present invention,

The measured specific surface area by the BET method 5 0 771 ^2/3 or more good or to rather is Ru der 1 0 0 m ² or more. Here, the BET method refers to a method of calculating the specific surface area of a solid using a BET adsorption isotherm.

When the specific surface area is less than 50 m, the adsorption efficiency is low when the alkali metal is added, and the crystallization speed during the heat treatment is low.

If the raw material used in the method of the present invention is amorphous, either dry powder or wet powder having attached moisture can be used.

First, the crystallization process of amorphous silicon will be described. The amorphous silica is crystallized by heating at a temperature of 900 ° C. or more. The crystal form produced by heating is in most cases a Usuburite type. However, the crystal form of the amorphous silica used in the present invention is a crystal ballast. It is not limited to a type, but may be another crystal form, for example, a trismite type.

If the amorphous silica force is used as it is as a raw material in the next step of ripening and growing, the dissolution rate of silica becomes excessive, and the Precipitation of silica ♦ Trouble such as adhesion occurs. Therefore, in order to control the dissolution rate of silica, the silica as a raw material needs to be partially crystallized. Regarding the degree of crystallinity, it is preferable that the degree of crystallinity measured by the X-ray diffraction method is 100%, but an amorphous portion may remain.

The temperature of the heat treatment is in the range of 900 to Ί600), and it is desirable that the temperature be as low as possible within this range. The higher the heating temperature, the greater the amount of ripeness required, and the higher the heating temperature. More undesirable impurities are incorporated.

In particular, in order to crystallize amorphous silica containing no alkali metal, a heat treatment at 150 ° C. or more is required, and therefore, consideration must be given to prevention of contamination by impurity contamination.

The crystallization rate of amorphous silica increases as the processing temperature increases and as the content of the alkali metal in the amorphous silica increases. Therefore, when the content of the alkali metal in the amorphous silica is increased, the amorphous silicon force can be crystallized by heat treatment at a low temperature.

The alkali metal is a group consisting of Na, K, and Li. At least one alkali metal selected from the group consisting of at least one alkali metal increases the crystallization speed of amorphous silica even at a small amount. Therefore, crystallization is possible without contamination by other substances.

In the method of the present invention, the amorphous silica as a raw material is at least 5 PPm or more so that it can be crystallized by heat treatment at a low temperature. It is preferable to contain the alkali metal. When the content of the alkaline metal is less than 5 ppm, the effect of increasing the crystallization rate of the amorphous silica is small.

The concentration of the alkali metal in the amorphous silica is determined by using at least one kind of water-soluble salts such as hydroxides and carbonates containing the above-mentioned alkali metal as a raw material. It can be adjusted by adding to all of the amorphous series force.

These aluminum metals are selectively adsorbed and concentrated on the amorphous silicon having a large specific surface area, act as a crystal nucleating agent during heat treatment, and become amorphous silicon. Increase the crystallization rate of mosquito.

As a method of adding the alkali metal to the amorphous silica, a method of immersing the amorphous silica in an aqueous solution containing the alkali metal, a method of adding the alkali metal to the amorphous silica, There are methods such as spraying an aqueous solution. Among these methods, the immersion method is simple, and a certain amount of alkali metal can be uniformly impregnated and adsorbed on amorphous silica particles.

When the amorphous silica is manufactured by a wet method, In the final step of washing the amorphous silica, the amorphous silica is washed with the washing liquid containing the alkaline metal to thereby remove the amorphous silica. It is reasonable to impregnate and adsorb mosquitoes with alkali metals.

When the alkali metal is impregnated into the amorphous silica, the temperature is not particularly limited, but is usually in the range of room temperature to 50.

The crystallinity of the crystalline silica obtained by heating the amorphous silica force depends on the content of the alkali metal in the amorphous silica and the temperature of the heat treatment. It can be adjusted appropriately depending on the combination of time and time.

The time of the ripening treatment is not particularly limited, and an appropriate condition may be selected depending on the temperature and the metal content. Usually, the ripening time is 20 minutes or more, preferably in the range of 1 to 20 hours.

The amorphous silica container used for the heat treatment may be made of a material such as silicon carbide, magnesium, zirconia, or graphite if the treatment temperature is about 200 or more. Those consisting of are used. In addition, when the value is less than 1200, a material made of an alumina-based or mica-based material is used.

Above 1,200, it is better to avoid using containers made of aluminum-based materials, as contamination from AJ2 from containers into silica may occur. .

The atmosphere gas used for the heat treatment in the method of the present invention is preferably air for practical use, but is preferably oxygen, carbon dioxide, or the like. You can use it. If necessary, an inert gas such as nitrogen or argon can be used as the atmosphere gas. As long as it can maintain the silica at a predetermined temperature, heat treatment equipment such as a tubular furnace, a box furnace, a tunnel furnace, and a fluidized-bed furnace can be used as long as it can maintain the silica at a predetermined temperature. Can be used. Heating may be performed using electric heat, combustion gas, or the like.

Next, the process of growing artificial quartz will be described.

An artificial quartz crystal is grown using the crystalline strain obtained by the heat treatment.

The artificial quartz is grown by filling the bottom (melting zone) of a vertical pressure vessel with crystalline silica and suspending the seed crystal in the upper zone (growing zone), and as a solvent, the volume of the container is reduced. Water filled with an aqueous alkaline solution with a volume of 75 to 85% and heated in a closed state, keeping the dissolution zone at a high temperature and the growth zone at a low temperature to create a temperature difference between the top and bottom of the vessel It can be done by the thermal temperature difference method.

Since the inside of the container becomes hot and under pressure, use a container that can withstand a pressure of 気圧 Ί Ο Ο to 150 atm.

The saturated solution of Si02 obtained by dissolving the crystalline series force in the aqueous solution in the dissolution zone causes the convection due to the temperature difference above and below the vessel. As it rises and enters the growth zone, it becomes a supersaturated solution of Sio 2 because of its low viscosity. In the growth region, an amount of Si 0 o corresponding to the difference between the solubility at a high temperature and the solubility at a low temperature is deposited on the seed crystal surface, and the crystal grows to grow human crystal.

The higher the temperature in the growth zone, the higher the crystal growth rate. However, if it is too long, "slice" is likely to occur. Normally, the temperature of the growth zone is selected in the range of 300 to 400 ° C.

The larger the temperature difference between the top and bottom of the vessel, the greater the crystal growth rate. However, if it is too large, the difference between the crystal growth rate in the upper part of the growth region and the crystal growth rate in the lower part becomes large. Usually, it is selected in the range of 20 to 40.

The cultivation time is about 0 days for small ones and more than 4 months for large ones.

The aqueous alkali solution is used to dissolve the crystalline silica in the growing process. The solutes in the aqueous alkali solution are Na, L (, K and other alkali metal hydroxides, carbonates, bicarbonates, shelf salts, phosphates, sulfates, halides, and fatty acid salts. There is at least one member selected from the group: this solute acts as a mineralizer.

In addition, in the case where the alkali metal is added and the heat treatment is performed in the crystallization process of the amorphous silica, the crystalline metal obtained by adding the alkali metal is obtained. It is preferable to use an aqueous solution of the same type of metal as the metal added in the crystallization step because it remains in the crystallization step.

As an alkali metal in the crystallization process of amorphous silica! In the case of using, any kind of aqueous alkali solution can be used. Since Li ions have an effect of improving the quality of artificial quartz, it is advantageous to use i-containing crystal silica for producing high-quality artificial quartz.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. explain .

(Example 1)

Specific surface area: 850 m ² / ^ (BET method), particle size range: 30 to 400 x / m, Al, Al, Al, Al and other alkaline Amorphous silica (containing 8% water) with a metal content of Ίppm or less was used as a raw material.

A solution for impregnation of alkali metal (Na) was prepared by mixing a 0.1 N—NaOH aqueous solution and ion exchanged water 905 ^. The amorphous silica 873 was immersed in the liquid maintained at a temperature of 50, and subjected to an impregnation treatment for 1 hour with stirring at 50 ° C. Then, the liquid component was separated by a centrifugal separator, and the Na-impregnated amorphous silica was dried overnight at about 50 ° G.

The Na-impregnated amorphous silica before drying had a liquid content of about 50% and a Na adsorption rate of 300 ppm based on the dry amorphous silica. The weight of the dried Na-impregnated amorphous silica was 86.5 §f.

Next, the Na-impregnated amorphous silica 303 is filled into an aluminum lippo (6ΩΒΦΧ7.5 on H) and heated at about 200Ί * Ό for 1 hour. After that, it was cooled down to room temperature.

The obtained crystalline silica had a specific gravity of 2.33, and the result of X-ray diffraction confirmed that it had a crystal-palitate structure. The crystalline silica contained, as impurities, 180 ppm of Na, and 1 ppm or less of each of AJ2, Ti, and alkali metals other than Na.

The obtained crystalline silica of the crystal-parallel type structure 20 Using 3 as a raw material, artificial quartz was grown by the ripening temperature difference method.

Use a 1 N one N a ₂ C 0 ₃ aqueous solution 7 5% Kyuseki of the alkaline aqueous solution ingenuity over Bok click-les-loop within the volume are found have use for dissolving the crystalline sheet Li Ca As a seed crystal, a Y-bar was used.

The temperature of the melting zone was 380, and the temperature of the growing zone, in which the seed crystal was suspended, was 350 ° C.

No inclusion was found in the obtained artificial quartz, and the content of A by inductively coupled plasma-atomic emission spectrometry (ICP-AES) was 1.0 ppm.

(Comparative Example 1 1)

The heat treatment for crystallization of the amorphous silica was not performed, and the artificial quartz was grown using the amorphous silica itself. Was repeated. As a result, polycrystalline α-crystal was deposited on the inner wall of the seed cup, and almost no growth of seed crystal was observed.

(Example 1-2)

Except that various concentrations of NaOH aqueous solution were used, the same treatment as in Example 10 was repeated using the amorphous silica in the same lot as that used in Example 11. Returning gave silicas with different amounts of impregnated Na. Each of these Na-impregnated silicas was subjected to heat treatment at the temperatures shown in Table 11 for about 10 hours. Under any conditions, the crystalline silica having a crystal-parallel type structure was obtained. was gotten . Next, artificial quartz was grown under the same conditions as in Example 11 using the obtained crystalline silica. As a result, artificial quartz was grown. Table 1 shows the results. Table 1

* 1… Value for amorphous silica

(Example 13)

The same procedure as in Example 1 was repeated except that various kinds of alkali metal impregnating solutions were used, and the amorphous silica in the same lot as in Example 11 was used. Thus, various alkali metal-impregnated amorphous silicas were obtained.

These alkali metal-impregnated amorphous silicas were heated to a temperature of 120 When heat treatment was performed at 0 for 10 hours, a silica crystal with a crystal-parallel structure was obtained.

Next, artificial quartz was grown using the obtained crystalline silica under the same conditions as in Example-1. The results are shown in Table 1. Table 2.

* 1 ... Value for amorphous silica

(Example — 4)

Keisanso over da # No. 3 (JIS Κ 1 4 08, 3 No. _{equivalent, S i 0 2: 28%} , N a 2 0: 9%) 6 a was warmed to 5 0 flashing pressure dehydration and _{concentrated, S i 0 2: 3 2} % fiberizing stock solution: was obtained (viscosity of approximately 1 0 0 Boi's (3 0)) '.

After filtering this stock solution, the extruder is used to pass through a gold-platinum alloy nozzle with a hole diameter of 0.1 mm and a hole diameter of 0.1 mm using an extruder. Then, it was extruded at a speed of 6 mZ into a coagulation bath (1N monosulfuric acid aqueous solution 20 ^) held at 50.

The extruded stock solution was dealkalized and solidified, and turned into a transparent fiber gel.

The obtained fibrous gel 103 was immersed in a treatment solution (1N-sulfuric acid aqueous solution 125 / ηδ), and treated with 100 for 3 hours with stirring.

Next, the obtained short arrow-shaped silica was immersed in pure water 250 and stirred for 10 minutes, and then dehydrated using a nutche. Washing with pure water was repeated 5 times. The sulfate concentration in the obtained silica was less than 1 ppm.

The obtained silica was dried at 150 C overnight.

The silica obtained in this way is amorphous, and as impurities, 0.6 ppm of Na, 0.3 ppm of K, and Α · δ of 0.5 Pi or less. Was contained.

This amorphous silica was used in Example 1)! In this manner, a heat treatment was performed to obtain crystallized silica.

Using the obtained crystallized silica, artificial quartz was grown in the same manner as in Example 10. As a result, artificial quartz was grown. No inclusions were found in the obtained artificial quartz, and the Α ^ content was 0.9 ppm.

(One example embodiment 5) - Echirushi Li Ke one Bok _{[S i (0 C 2 H} 5) 4; Wako Ke unvulcanized Le .: reagent special grade] 1 0 4 g, d data Roh Lumpur: Ί Ο Ο Λ Jun Water: 36, HC: 0.3 mol (vs. ethyl alcohol) ) Was added, the mixture was stirred for 30 minutes, kept at a temperature of 30 for 1 day, and then the produced silica was separated using a nutsche. The obtained powdery silica was immersed in pure water: 1000, stirred for 10 minutes, and then dehydrated using a nutsche. The washing with pure water was repeated five times. The concentration of C ^ in the obtained soldering force was less than ΊPPm.

The resulting silica was dried overnight at 105.

The silica obtained in this way is amorphous, and as impurities, Na of less than 0.3 ppm, K of less than 0.1 ppm, and A ^ of less than 0.5 ppm. Contained.

This amorphous silica was subjected to a heat treatment in the same manner as in Example 11 to obtain crystallized silica.

An artificial crystal was grown in the same manner as in Example 11 except that the obtained crystallized silica was used, and an Na0H aqueous solution was used as a solvent. As a result, artificial quartz was grown. Inclusions were found in the obtained quartz, and the A content was _0.8 ppm.

Claims

The scope of the claims

1. Manufacture of human quartz by hydrothermal growth, including the use of crystalline silica obtained by heating amorphous silica as a raw material Manufacturing method of artificial quartz.

2. The method according to claim 1, wherein the crystalline silica mainly has a crystal ballistic structure.

3. The artificial quartz according to claim 1 or 2, wherein the content of the alkali metal, the alkaline earth metal and the transition metal as impurities in the amorphous silica is about 0 ppm or less. Manufacturing method.

4. The method for producing artificial quartz according to claim 1, wherein the A ^ content in the amorphous silica is 5 ppm or less.

5. The specific surface area of amorphous Shitsushi Li mosquitoes measured by the BET method, 5 0 m ^2/3 or more der Ru claim 1 or 2 method of synthetic quartz manufacturing description.

6. The method for producing artificial quartz according to claim 1, wherein the specific surface area of the amorphous silica measured by the BET method is about 0 ° ² ng or more.

7. crystalline sheet re mosquito artificial lens amorphous Shitsushi Li mosquitoes to ^{9 0 0~ 1 6 0 0 e} C range claim 1 or obtained we are by the and this heating at a temperature of 2, wherein Manufacturing method.

8. The method of claim 2, wherein the crystalline silica is obtained by heating an amorphous silica in the presence of an alkali metal.

9. Whether the alkali metal is a group consisting of Na, K. Li 9. The method for producing an artificial crystal according to claim 8, wherein the method is at least one selected from the group consisting of:

10. The method according to claim 8, wherein the concentration of the alkali metal in the amorphous silica is 5 η or more.

11. The method for producing a synthetic quartz according to claim 2 or 3, wherein the temperature of the crystal growth region in the hydrothermal growth step is in the range of 300 to 400.

12. The method of claim 1 or 2, wherein the temperature of the growth zone of the crystal is 20 to 40 lower than the temperature of the melting zone of the crystalline silica in the ripening and growing step. .

13. In the hydrothermal growth process, the solute of the aqueous alkali solution, such as the solvent of the crystalline silica, is converted to an alkali metal hydroxide, carbonate, bicarbonate, phosphate, phosphate, vinegar. 3. The method for producing an artificial quartz according to claim 1 or 2, wherein the method is at least one selected from the group consisting of cut salt, halide and fatty acid salt.

14. The method for producing an artificial quartz according to claim 1 or 2, wherein the amorphous silica is obtained by the following method (1) or (2):

Α) A general formula having a viscosity in the range of 2 to 500 voids:

Μ 20 ♦ n Si 0 ₂ (where M represents an alkali metal and n is the number of moles of Si 02 in the range of 0.5 to 5) An aqueous solution of an acid salt is extruded through a spinning nozzle having a pore size of 1 mm or less into a water-soluble organic medium or a coagulation bath composed of an acid solution having a filtration rate of 4 N or less to form a fiber. After coagulation, the resulting fibrous gel is treated with a solution containing acid, To remove impurities by washing with water:

8) The silica obtained by the above method A) is further added to 10

A method in which heat treatment is performed at a temperature of 00 ° G or more.