【発明の詳細な説明】[Detailed description of the invention]
産業上の利用分野
本発明は多孔質ガラス膜を製造する際の原料ガ
ラス成形する時の雰囲気と熱処理時の雰囲気の温
湿度制御に関するものである。
従来技術との関係
多孔質ガラスの製造法に関しては既に種々の手
段が試みられている。例えば多孔質ガラスはホウ
ケイ酸ソーダガラス（原料ガラス）に適切な熱処
理を施し、SiO2相とB2O3−Na2O相に分相させ、
その後HCl、H2SO4等の酸に浸漬し、酸に可溶な
B2O3−Na2O相を抽出することによつて得られ
る。得られた多孔質ガラスはガス分離膜、逆浸透
膜、限外過膜等の分離膜としての用途のほか吸
着剤、触媒担体等の用途がある。しかしながら多
孔質ガラスを膜として用いる場合最も問題となる
のは膜の表面状態である。すなわち原料ガラスを
溶融し板状、管状、繊維状等の希望する形成に成
形し、その後熱処理を施すと、ガラス表面に内部
ガラス組成とは異なるSiO2に富むガラス組成の
スキン層が生じる。このスキン層は酸処理を行つ
ても多孔質化がほとんどなされずそのまま残存す
る。そのため分離膜として用いた場合、スキン層
は流体透過に対して大きな抵抗となり、透過流量
を減少させる。しかも酸処理時にもスキン層が
B2O3−Na2O相の抽出の抵抗となり処理時間が長
くなる。またスキン層が内部ガラス組成とは異な
るため酸処理時にスキン層にクラツクが生じ強度
低下の原因となつていた。
発明の目的
而して本発明者らはこのスキン層の厚みが成形
時の雰囲気の温湿度および熱処理時の雰囲気の湿
度によつて変わるこれに注目して成形時熱処理時
の雰囲気の温湿度を制御することで表面スキン層
の厚みを透過流量や酸処理時の割れに影響がない
ほどに薄くできることを見い出し、本発明に至つ
た。
発明の構成
即ち、本発明は成形時の雰囲気を温度10℃以
下、絶対湿度５ｇH2O／Kg・dryair以下、および
熱処理時の雰囲気を絶対湿度５ｇ−H2O／Kg・
dryair以下にする点に要旨をおくもので、これに
よつて表面スキン層の厚みが透過流量を減少させ
たり、酸処理時の割れの原因とならないほどに薄
くすることができた。この際表面スキン層の生成
が雰囲気中の水分の吸着、水分とB2O3−Ba2Oの
反応、水分のガラス中の拡散と関係づけられるこ
とから温度、湿度は低ければ低いほど好ましいが
上記の温・湿度以下であれば充分目的は達せられ
る。
この様に本発明は多孔質ガラス膜の原料ガラス
（SiO2、B2O3、Na2O、Al2O3等の組成よりなる）
を用い成形、熱処理を行なつてSiO2相とB2O3−
Na2O相に分相させ、その後酸（例えばHCl、
H2SO4）に浸漬して多孔質化するものであるが、
この場合重要なことは上記成形、熱処理時の雰囲
気を特定化することにある。つまり成形時の雰囲
気として温度が10℃をこえたり、又絶対湿度が５
ｇ−H2O／Kg・dryairをこえるといずれの場合も
表面スキン層の厚みを薄くすることは困難であつ
た。さらに成形後の熱処理の際の湿度も５ｇ−
H2O／Kg・dryairをこえるとスキン層の厚みが薄
くできず好ましくない。尚、紡糸成形、熱処理に
用いる装置には特別制約を設けるものではない。
発明の効果
本発明に従い、成形時熱処理時に温度、湿度制
御を行い多孔質ガラス膜を製造したところ制御し
ない場合と較べてガス透過流量が２倍となり実用
性に富む多孔質ガラス膜を得ることができた。
実施例
実施例 １
SiO262.5wt％、B2O327.3wt％、Na2O7.2wt％、
Al2O33.0wt％からなる原料ガラスを白金ノズル
内で1000℃で再溶融し、ノズル口からガラスを引
き出し外径２mm、内径１mmの中空ガラス管に成形
した。この成形時の雰囲気を温度８℃、絶対湿度
４ｇ−H2O／Kg・dryairに制御した。得られた中
空ガラス管を580℃に温度コントロールされた電
気炉内で24時間熱処理した。この時の雰囲気も絶
対湿度４ｇH2O／Kg・dryairに制御した。その後
IN−H2SO4を用いて90℃で48時間処理して多孔
質化した。流水で充分洗浄した後乾燥させた。こ
のようにして得られた多孔質ガラス膜のH2、N2
ガスの単位時間、膜面積・圧力当たりのガス透過
流量を測定すると表１に示す値となつた。成形
時、熱処理時に温湿度制御なしのものを酸処理し
て得られたもの、また温湿度制御なしで成形、熱
処理しその後５％弗酸溶液で表面スキン層を除去
して酸処理したものの膜性能も併わせて示す。な
お、これら比較の場合の成形時の雰囲気は20℃、
絶対湿度９ｇ−H2O／Kg・dryairであり熱処理時
の雰囲気は絶対湿度９ｇH2O／Kg・dryairであつ
た。
INDUSTRIAL APPLICATION FIELD The present invention relates to temperature and humidity control of the atmosphere during molding of raw material glass and the atmosphere during heat treatment when producing a porous glass membrane. Relationship with Prior Art Various methods have already been tried for producing porous glass. For example, porous glass is produced by subjecting soda borosilicate glass (raw material glass) to appropriate heat treatment to separate the phases into two SiO phases and a B 2 O 3 -Na 2 O phase.
After that, it is immersed in an acid such as HCl, H 2 SO 4 , etc.
Obtained by extracting the B 2 O 3 −Na 2 O phase. The obtained porous glass can be used not only as separation membranes such as gas separation membranes, reverse osmosis membranes, and ultrafiltration membranes, but also as adsorbents, catalyst carriers, and the like. However, when porous glass is used as a membrane, the most important problem is the surface condition of the membrane. That is, when raw glass is melted and formed into a desired shape such as a plate, tube, or fiber, and then heat-treated, a skin layer with a glass composition rich in SiO 2 that is different from the internal glass composition is formed on the glass surface. Even if this skin layer is subjected to acid treatment, it remains as it is without becoming porous. Therefore, when used as a separation membrane, the skin layer provides a large resistance to fluid permeation, reducing the permeation flow rate. Moreover, even during acid treatment, the skin layer remains
This creates resistance to the extraction of the B 2 O 3 −Na 2 O phase and increases the processing time. Furthermore, since the skin layer has a different composition from the internal glass, cracks occur in the skin layer during acid treatment, causing a decrease in strength. Purpose of the Invention The present inventors have focused on the fact that the thickness of the skin layer changes depending on the temperature and humidity of the atmosphere during molding and the humidity of the atmosphere during heat treatment, and have investigated the temperature and humidity of the atmosphere during heat treatment during molding. It has been discovered that by controlling the thickness of the surface skin layer, it can be made so thin that it has no effect on the permeation flow rate or cracking during acid treatment, leading to the present invention. Structure of the Invention That is, the present invention sets the atmosphere during molding to a temperature of 10° C. or less and an absolute humidity of 5 g H 2 O/Kg dry air, and the atmosphere during heat treatment to an absolute humidity of 5 g H 2 O/Kg dry air.
The key point was to make the surface skin layer less than dryair, which made it possible to reduce the thickness of the surface skin layer to the extent that it did not reduce the permeation flow rate or cause cracking during acid treatment. At this time, the lower the temperature and humidity, the better, since the formation of the surface skin layer is related to the adsorption of moisture in the atmosphere, the reaction between moisture and B 2 O 3 −Ba 2 O, and the diffusion of moisture in the glass. If the temperature and humidity are below the above, the purpose can be achieved. As described above, the present invention uses raw material glass (composed of SiO 2 , B 2 O 3 , Na 2 O, Al 2 O 3 , etc.) for porous glass membranes.
Molding and heat treatment are performed using SiO 2 phase and B 2 O 3 −
Phase separation into Na 2 O phase followed by addition of acid (e.g. HCl,
H 2 SO 4 ) to make it porous.
In this case, what is important is to specify the atmosphere during the molding and heat treatment. In other words, the temperature during molding may exceed 10℃, or the absolute humidity may exceed 5℃.
In any case, it was difficult to reduce the thickness of the surface skin layer when g-H 2 O/Kg.dryair was exceeded. Furthermore, the humidity during heat treatment after molding was 5g-
If the amount exceeds H 2 O/Kg/dryair, the thickness of the skin layer cannot be made thinner, which is not preferable. Note that there are no special restrictions on the equipment used for spinning and forming and heat treatment. Effects of the Invention According to the present invention, when a porous glass membrane was manufactured by controlling the temperature and humidity during heat treatment during molding, the gas permeation flow rate was doubled compared to the case without control, making it possible to obtain a highly practical porous glass membrane. did it. Examples Example 1 SiO 2 62.5wt%, B 2 O 3 27.3wt%, Na 2 O 7.2wt%,
Raw material glass consisting of 3.0 wt% Al 2 O 3 was remelted at 1000°C in a platinum nozzle, and the glass was pulled out from the nozzle opening and formed into a hollow glass tube with an outer diameter of 2 mm and an inner diameter of 1 mm. The atmosphere during this molding was controlled to a temperature of 8° C. and an absolute humidity of 4 g-H 2 O/Kg dry air. The obtained hollow glass tube was heat-treated for 24 hours in an electric furnace whose temperature was controlled at 580°C. The atmosphere at this time was also controlled to an absolute humidity of 4 g H 2 O/Kg dryair. after that
It was treated with IN-H 2 SO 4 at 90° C. for 48 hours to make it porous. It was thoroughly washed with running water and then dried. H 2 , N 2 of the porous glass membrane thus obtained
When the gas permeation flow rate per unit time, membrane area and pressure was measured, the values shown in Table 1 were obtained. Films obtained by acid treatment without temperature and humidity control during molding and heat treatment, and films obtained by molding and heat treatment without temperature and humidity control, then removing the surface skin layer with a 5% hydrofluoric acid solution and acid treatment. Performance is also shown. In addition, the atmosphere during molding for these comparisons was 20℃,
The absolute humidity was 9 g-H 2 O/Kg dry air, and the atmosphere during the heat treatment was 9 g H 2 O/Kg dry air.
【表】
測定したときの値である。
[Table] Values when measured.