JP3662311B2 - Method for producing silica glass for filter - Google Patents
Method for producing silica glass for filter Download PDFInfo
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- JP3662311B2 JP3662311B2 JP27510095A JP27510095A JP3662311B2 JP 3662311 B2 JP3662311 B2 JP 3662311B2 JP 27510095 A JP27510095 A JP 27510095A JP 27510095 A JP27510095 A JP 27510095A JP 3662311 B2 JP3662311 B2 JP 3662311B2
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- silica glass
- filter
- temperature
- raw material
- closed cells
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- Filtering Materials (AREA)
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Description
【０００１】
【産業上の利用分野】
本発明は、フィルター用シリカガラスの製造方法、さらに詳しくは高温又は腐食性液体等、通常の濾過装置では処理し難い液体類を濾過精製するための濾材、或は高温ガス、腐食性ガス等の反応性の高いガスの流量調節のためのフィルター用シリカガラスの製造方法に係る。
【０００２】
【従来の技術】
シリカガラスは、高純度で、耐熱性、耐薬品性、耐熱衝撃性に優れているところから、例えば高温で使用される半導体素子製造用治具、或は高温又は腐食性液体やガスの濾材或は流量調節用フィルター等として、幅広く利用されている。前記高温又は腐食性液体やガスの濾材或は流量調節用フィルターとしては、例えば石英ガラス粉を焼結したフィルター、石英ガラスファイバーの織物又は不織布を加工したフィルター、或は石英ガラス発泡体を加工したフィルター（特開平３ー２４７５２４号公報）等が提案されている。しかしながら前記フィルターのうち焼結手段で作成したフィルターは、加熱焼結中に予備成形された成形体が収縮し、所望の形状のフィルターを寸法精度良く作成できない欠点があった。また、石英ガラスファイバーの織物或は不織布を加工したフィルターは、形状維持性に難点があるばかりでなく、多くの製造工程を必要とし、石英ガラスが有する高純度で安定性に優れた利点が損なわれ易いという欠点があった。さらに、前記特開平３ー２４７５２４号公報に記載の石英ガラス発泡体を基体とするフィルターは、発泡剤による異常発泡が部分的に発生し、均質な発泡体が得られないところから、液体やガスを濾過する位置の設定が困難であるという欠点があった。
【０００３】
【発明が解決しようとする課題】
こうした現状に鑑み、本発明者等は、高温又は腐食性液体やガスの濾材或は流量調節用フィルターについて鋭意研究を重ねた結果、特定の独立気泡を含有する不透明シリカガラスを浸食して独立気泡の一部を連通気泡とすることで、特段の加工もなく高温又は腐食性液体やガスを所定の位置から放出できるフィルターが得られることを見出し本発明を完成したものである。すなわち
【０００４】
本発明は、高温又は腐食性液体やガスの濾材或は流量調節に用いるフィルター用シリカガラスの製造方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
上記目的を達成する本発明は、石英原料粉を耐熱性型枠内に充填したのち、室温から前記石英原料粉の溶融する温度より１０〜８０℃高い温度までをゆっくり昇温して微細な独立気泡が分散する不透明シリカガラスを製造し、次いで前記不透明シリカガラスを浸食し、独立気泡の一部を連通気泡とするフィルター用シリカガラスの製造方法に係る。
【０００６】
本発明の製造方法で使用する石英原料粉は、高純度の石英原料粉であって、粒度が１０〜３５０μｍの範囲の結晶質石英粉又は非晶質石英粉である。前記石英原料粉を耐熱性型枠内に充填したのち、不活性ガス雰囲気下で加熱溶融することで独立気泡が分散する不透明シリカガラスが得られる。特に、好ましくは５〜２０リットル／分の窒素ガスを流しながら室温から石英原料粉の溶融する温度より５０〜１５０℃低い温度までを１０〜５０℃／分の昇温速度で、前記温度を超え石英原料粉の融点より１０〜８０℃高い温度までを１０℃／分以下の昇温速度で昇温し溶融すると、直径１〜２０００μｍ、好ましくは１０〜１０００μｍの独立気泡が１０，０００〜２，０００，０００個／ｃｍ3、好ましくは１００，０００〜１，０００，０００個／ｃｍ3均一に分散し、嵩密度が１．０ｇ／ｃｍ3以上の不透明シリカガラスが製造できる。前記不透明シリカガラスを次いで浸食すると独立気泡の一部が連通気泡となり、そこから液体が流通するフィルター用シリカガラスが得られる。前記浸食には酸又はアルカリ溶液が用いられるが、酸としては弗化水素酸、硝酸、塩酸、硫酸、リン酸又はこれらの酸の混合液が、またアルカリとしては、アンモニア、水酸化ナトリウム、メタリン酸ナトリウムがよい。前記溶液の濃度は特に限定されないが、高濃度の溶液を用いれば処理時間が短くてよく、また溶液を加熱或は加圧すれば浸食時間を短縮することができる。本発明の製造方法で得られたフィルター用シリカガラスは、高純度で、耐熱性、耐薬品性、耐熱衝撃性等に優れている上に、該シリカガラスで形成したフィルターは寸法精度が高いところから、高温又は腐食性液体やガスの濾材或は流量調節用フィルターとして有用である。本発明で製造された不透明シリカガラスの気泡が小さい時には、減圧下又は真空下で再加熱して独立気泡の直径を大きくした上で浸食するのがよい。
【０００７】
上記製造方法で得られた不透明シリカガラスに分散する独立気泡の直径が１μｍ未満のシリカガラスは製造が難しく、また直径が２０００μｍを超えると得られたシリカガラスの機械的強度が低下し実用的なフィルターが得られない。独立気泡の含有量が１０，０００個／ｃｍ3未満では、連通気泡の開口部の形成が少なくフィルター性能が劣り、また独立気泡の含有量が２，０００，０００個／ｃｍ3を超えるとシリカガラスの機械的強度が低下する。さらに、シリカガラスの嵩密度が１．０ｇ／ｃｍ3未満では機械的強度が低く、浸食時にボロボロになる。
【０００８】
また、溶融加熱には、ＯＨ基の混入が少ない電気溶融法が好ましい。使用する耐熱性型枠としては、カーボン製型枠、セラミック製型枠、または前記型枠内に挿入された透明石英ガラス管等が挙げられる。特に、透明石英ガラス管の使用は、原料の高純度が維持されるとともに、製造されるシリカガラスに形崩れが起らず良好なシリカガラスが得られる。
【０００９】
【実施の形態】
以下、実施例に基づいてを本発明を具体的に説明するが、本発明はこれに限定されるものではない。
【００１０】
【実施例】
実施例１
内径２７０ｍｍ、高さ３００ｍｍのグラファイト製枠内に外径２７０ｍｍ、肉厚４ｍｍ、高さ３００ｍｍの石英ガラス管を挿入した。この石英ガラス管に粒径が５０〜２００μｍ、平均粒径が約１００μｍ、嵩密度が１．４ｇ／ｃｍ3の天然石英結晶粉（融点１７５０℃）を充填し、それを電気炉内に設置し、１０-2ｔｏｒｒ以下に真空排気して粒子間に残留している空気を除去した。次いで、炉内を窒素で真空破壊し、１０リットル／分の流量で窒素ガスを流しながら室温から１，２００℃までを１２０分で、１，２００℃から１，６３０℃までを９０分で、１，６３０℃から１，７５０℃までを２４０分で昇温させ、次いで１７５０℃に保持しながら６０分加熱した後、加熱を止めて室温まで冷却し、シリカガラスブロックを取り出した。得られたシリカガラスブロックから厚さ１ｍｍの薄板をバンドソーでカットした。得られた薄板の独立気泡の直径、気泡含有量及び密度を測定したところ、表１に示すとおりであった。
【００１１】
上記不透明シリカガラス薄板を２５％弗化水素酸溶液で３時間エッチングしたところランダムに連通気泡の開口部を有するシリカガラスが得られた。
【００１２】
実施例２
実施例１で得られた不透明シリカガラスを１０-2ｔｏｒｒ以下の減圧雰囲気中で１７２０℃に１分間加熱した。加熱後の不透明シリカガラスの独立気泡の直径、気泡含有量及び密度は、表１に示すとおりであった。
【００１３】
上記不透明シリカガラスを実施例１と同様に浸食処理を行ったところ、連通気泡の開口部は実施例１の２倍であった。
【００１４】
比較例１
実施例１において、天然石英結晶粉を加熱する雰囲気を減圧とした以外、実施例１と同様に加熱してシリカガラスを製造した。得られたシリカガラスは半透明であり、分散する気泡の直径、気泡含有量及び密度は表１のとおりであった。
【００１５】
上記半透明のシリカガラスを実施例１と同様の条件で浸食処理したところ、連通気泡の開口部は全くみられず、また液体の通過も認められなかった。
【００１６】
比較例２
特開平３−２４７５２４号公報記載の製造方法に準じた製造方法で、発泡体を製造した。発泡体の独立気泡の直径、気泡含有量及び密度は表１に示すとおりである。
【００１７】
上記発泡体を実施例１と同様の条件で浸食処理を行ったところ、連続気泡の分布が均一でなく、一部に大きな開放泡が確認され、また強度が低く取扱時に端が欠けてしまった。
【００１８】
【表１】
【発明の効果】
本発明の製造方法では、微細な独立気泡が分散するとともに一部に連通気泡が存在する不透明シリカガラスが得られる。前記不透明シリカガラスは、高純度で、耐熱性が高く、部分的に連通気泡が開口しているので、高温又は腐食性液体又はガスを濾過又は流量調節できるフィルター用素材として利用できる。前記シリカガラスから作成されたフィルターは、作成時に収縮が起らず寸法精度が高い上に、異常発泡もなくフィルターから放出する濾液等の位置設定が容易である。[0001]
[Industrial application fields]
The present invention relates to a method for producing silica glass for a filter, more specifically, a filter medium for filtering and purifying liquids that are difficult to process with a normal filtration device such as high temperature or corrosive liquid, or high temperature gas, corrosive gas, etc. The present invention relates to a method for producing silica glass for a filter for adjusting the flow rate of a highly reactive gas.
[0002]
[Prior art]
Silica glass has high purity and is excellent in heat resistance, chemical resistance, and thermal shock resistance. For example, it is a jig for manufacturing semiconductor elements used at high temperatures, or a filter medium for high temperature or corrosive liquids or gases. Is widely used as a flow control filter. Examples of the high temperature or corrosive liquid or gas filter medium or the flow rate adjusting filter include a filter obtained by sintering a quartz glass powder, a filter obtained by processing a woven or nonwoven fabric of quartz glass fiber, or a quartz glass foam. A filter (Japanese Patent Laid-Open No. 3-247524) has been proposed. However, the filter prepared by the sintering means among the above filters has a drawback that a preform formed during heat sintering shrinks and a filter having a desired shape cannot be formed with high dimensional accuracy. In addition, a filter made of quartz glass fiber woven fabric or non-woven fabric has not only difficulty in maintaining shape but also requires many manufacturing processes, and the high purity and stability advantages of quartz glass are impaired. There was a drawback that it was easy to get. Further, the filter based on the quartz glass foam described in Japanese Patent Application Laid-Open No. 3-247524 has abnormal foaming caused by a foaming agent in part and a homogeneous foam cannot be obtained. There is a drawback that it is difficult to set the position for filtering the slag.
[0003]
[Problems to be solved by the invention]
In view of the current situation, the present inventors have intensively studied high temperature or corrosive liquid or gas filter media or flow rate control filters, and as a result, eroded opaque silica glass containing specific closed cells and closed cells. The present invention has been completed by discovering that a filter capable of releasing a high temperature or corrosive liquid or gas from a predetermined position without special processing can be obtained by forming a part of the bubbles as communicating bubbles. That is, [0004]
An object of this invention is to provide the manufacturing method of the silica glass for filters used for the filter medium of high temperature or corrosive liquid, or gas, or flow volume adjustment.
[0005]
[Means for Solving the Problems]
The present invention that achieves the above-mentioned object is the method of filling the quartz raw material powder in a heat-resistant mold, and then slowly raising the temperature from room temperature to a temperature 10 to 80 ° C. higher than the melting temperature of the quartz raw material powder. The present invention relates to a method for producing a silica glass for a filter, in which an opaque silica glass in which bubbles are dispersed is produced, and then the opaque silica glass is eroded so that some of the closed cells are connected to the open cells.
[0006]
The quartz raw material powder used in the production method of the present invention is a high-purity quartz raw material powder, which is a crystalline quartz powder or an amorphous quartz powder having a particle size in the range of 10 to 350 μm. An opaque silica glass in which closed cells are dispersed is obtained by filling the quartz raw material powder in a heat resistant mold and then heating and melting it in an inert gas atmosphere. In particular, while flowing nitrogen gas at a rate of 5 to 20 liters / minute, the above temperature is exceeded at a temperature increase rate of 10 to 50 ° C./minute from room temperature to a temperature 50 to 150 ° C. lower than the temperature at which the quartz raw material powder melts. When the temperature is raised to a temperature 10-80 ° C. higher than the melting point of the quartz raw material powder at a heating rate of 10 ° C./min or less and melted, closed cells having a diameter of 1 to 2000 μm, preferably 10 to 1000 μm, are 10,000 to 2, 000,000 pieces / cm 3, preferably dispersed in 100,000 to 1,000,000 pieces / cm 3 uniform, the bulk density can be produced 1.0 g / cm 3 or more opaque silica glass. When the opaque silica glass is then eroded, some of the closed cells become open cells, and a silica glass for a filter through which a liquid flows is obtained. An acid or an alkali solution is used for the erosion, and hydrofluoric acid, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid or a mixture of these acids is used as the acid, and ammonia, sodium hydroxide, metalin is used as the alkali. Sodium acid is good. The concentration of the solution is not particularly limited, but if a high concentration solution is used, the treatment time may be short, and if the solution is heated or pressurized, the erosion time can be shortened. The silica glass for a filter obtained by the production method of the present invention has high purity, excellent heat resistance, chemical resistance, thermal shock resistance and the like, and the filter formed from the silica glass has high dimensional accuracy. Therefore, it is useful as a filter medium for high-temperature or corrosive liquids and gases, or as a filter for adjusting the flow rate. When the bubbles of the opaque silica glass produced by the present invention are small, it is preferable to reheat under reduced pressure or vacuum to increase the diameter of the closed cells and erode.
[0007]
Silica glass having a closed cell diameter of less than 1 μm dispersed in the opaque silica glass obtained by the above production method is difficult to produce, and if the diameter exceeds 2000 μm, the mechanical strength of the obtained silica glass is lowered and practical. A filter cannot be obtained. If the content of closed cells is less than 10,000 / cm 3 , the formation of open portions of open cells is small and the filter performance is inferior. If the content of closed cells exceeds 2,000,000 / cm 3 , silica The mechanical strength of the glass decreases. Furthermore, when the bulk density of silica glass is less than 1.0 g / cm 3 , the mechanical strength is low, and it becomes tattered during erosion.
[0008]
For melting and heating, an electric melting method with less OH group mixing is preferred. Examples of the heat-resistant mold used include a carbon mold, a ceramic mold, or a transparent quartz glass tube inserted into the mold. In particular, the use of the transparent quartz glass tube maintains the high purity of the raw material, and a good silica glass can be obtained without being deformed in the produced silica glass.
[0009]
Embodiment
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to this.
[0010]
【Example】
Example 1
A quartz glass tube having an outer diameter of 270 mm, a wall thickness of 4 mm, and a height of 300 mm was inserted into a graphite frame having an inner diameter of 270 mm and a height of 300 mm. This quartz glass tube is filled with natural quartz crystal powder (melting point 1750 ° C.) having a particle size of 50 to 200 μm, an average particle size of about 100 μm and a bulk density of 1.4 g / cm 3 , and installed in an electric furnace. The air remaining between the particles was removed by evacuating to 10 −2 torr or less. Next, the inside of the furnace was vacuum-breaked with nitrogen, while flowing nitrogen gas at a flow rate of 10 liters / minute, from room temperature to 1,200 ° C. in 120 minutes, from 1,200 ° C. to 1,630 ° C. in 90 minutes, The temperature was raised from 1,630 ° C. to 1,750 ° C. in 240 minutes, and then heated for 60 minutes while maintaining the temperature at 1750 ° C. Then, the heating was stopped and the mixture was cooled to room temperature, and the silica glass block was taken out. A thin plate having a thickness of 1 mm was cut with a band saw from the obtained silica glass block. When the diameter, bubble content, and density of closed cells of the obtained thin plate were measured, they were as shown in Table 1.
[0011]
When the opaque silica glass thin plate was etched with a 25% hydrofluoric acid solution for 3 hours, silica glass having openings of open cells was obtained at random.
[0012]
Example 2
The opaque silica glass obtained in Example 1 was heated to 1720 ° C. for 1 minute in a reduced-pressure atmosphere of 10 −2 torr or less. The diameter, the bubble content and the density of the closed cells of the opaque silica glass after heating were as shown in Table 1.
[0013]
When the opaque silica glass was subjected to erosion treatment in the same manner as in Example 1, the opening of the communicating bubbles was twice that in Example 1.
[0014]
Comparative Example 1
In Example 1, silica glass was produced by heating in the same manner as in Example 1 except that the atmosphere for heating the natural quartz crystal powder was reduced in pressure. The obtained silica glass was translucent, and the diameter, bubble content and density of the dispersed bubbles were as shown in Table 1.
[0015]
When the translucent silica glass was subjected to erosion treatment under the same conditions as in Example 1, no openings of communicating bubbles were observed, and no liquid was allowed to pass through.
[0016]
Comparative Example 2
A foam was produced by a production method according to the production method described in JP-A-3-247524. The diameter, the bubble content and the density of the closed cells of the foam are as shown in Table 1.
[0017]
When the foam was subjected to erosion treatment under the same conditions as in Example 1, the distribution of open cells was not uniform, large open bubbles were confirmed in some parts, and the strength was low and the edges were missing during handling. .
[0018]
[Table 1]
【The invention's effect】
In the production method of the present invention, it is possible to obtain an opaque silica glass in which fine closed cells are dispersed and some of the open cells are present. The opaque silica glass has high purity, high heat resistance, and partly open communication bubbles. Therefore, the opaque silica glass can be used as a filter material capable of filtering or adjusting the flow rate of high-temperature or corrosive liquid or gas. The filter made from the silica glass has high dimensional accuracy without causing shrinkage at the time of preparation, and it is easy to set the position of the filtrate discharged from the filter without abnormal foaming.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27510095A JP3662311B2 (en) | 1995-09-29 | 1995-09-29 | Method for producing silica glass for filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27510095A JP3662311B2 (en) | 1995-09-29 | 1995-09-29 | Method for producing silica glass for filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0986954A JPH0986954A (en) | 1997-03-31 |
| JP3662311B2 true JP3662311B2 (en) | 2005-06-22 |
Family
ID=17550771
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27510095A Expired - Fee Related JP3662311B2 (en) | 1995-09-29 | 1995-09-29 | Method for producing silica glass for filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3662311B2 (en) |
-
1995
- 1995-09-29 JP JP27510095A patent/JP3662311B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0986954A (en) | 1997-03-31 |
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