JPS59164648A - Production of porous glass - Google Patents

Abstract

PURPOSE:To produce porous glass having high SiO2 content and superior chemical and thermal stability by causing phase separation of raw materials consisting essentially of SiO2, B2O3, Na2O, and Li2O having specified proportion by heat treatment, followed by an acid treatment. CONSTITUTION:A mixture of raw materials for glass consisting of 41-64wt% SiO2, 28-51wt% B2O3, 4.5-13wt% Na2O, and <=3.5wt% Li2O, with <=0.5 ratio of Li2O/Na2O, as primary components; and 2-3wt% MoO3 and <=10wt% at least one kind among Al2O3, ZrO2, and MgO, both basing on the amt. of the primary component, as the adjustment component. The raw material for the glass is heat- treated in the temp. range causing no softening nor deformation, and an alkali metal borate phase is separated from a silica phase. Then, the alkali metal borate phase is eluted with H2SO4, etc. to obtain the porous glass. By this process, a porous glass having high SiO2 content and superior mechanical strength which contains no gelled silica, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing porous glass, and more particularly to a method for producing a high-silicate porous glass that does not contain gel-like silica precipitates within the pore structure.

Conventionally, high silicate porous glass is 5i02, B20
A raw material glass consisting of three components, B and Na2O, is separated into a finely entangled sodium borate phase and a silica phase, and the sodium borate phase is eluted with acid to form a three-dimensional glass consisting of an acid-insoluble silica phase. It was manufactured by a method of forming a network-like porous body.

However, the manufacturing method has the disadvantage that a small amount of silica contained in the sodium borate phase generated by phase separation becomes gel-like silica and precipitates in the pores of the porous body during acid elution. Ta.

Gel-like silica disturbs the porous structure derived from the phase separation structure,
This reduces the pore volume and the rate of fluid permeation through the porous material, so it is used in cases where precise control of pore properties is required, such as when using the porous material as a separation membrane or filter material, and This became a major obstacle when a high permeation rate was required.

In order to avoid such drawbacks, (a) a method of using sodium borosilicate glass with a low 8102 content as the raw material glass, and (o) a method of washing acid-leached porous glass with an alkaline solution to remove gel-like silica. A method was proposed to remove it.

However, in method (a), since the network structure of the silica phase is not sufficiently strong, the mechanical strength of the obtained porous body is low, and it is difficult to separate and form a membrane for practical use. was extremely difficult. In addition, because the compositions of gel-like silica and the porous body are similar, the porous body itself is eroded at the same time during 1-alcohol cleaning, making it unreasonable to produce a molded body with sufficiently high strength. Met.

In order to eliminate such conventional drawbacks, the present inventors first proposed a method of adding molybdenum oxide to sodium borosilicate glass, which is a promising raw material for porous glass, in Japanese Patent Application No. 57-2.
It was proposed as No. 2994.

According to this proposal, molybdenum oxide reduces the amount of silica contained in the sodium borate phase during phase separation, and furthermore, during acid elution, it reacts with the silica in the sodium borate phase to release soluble silica. Forms molybdenum particles to prevent precipitation of gel-like silica. Furthermore, molybdenum oxide has the effect of increasing the volume fraction of the silica phase in a phase-separated state and strengthening the network structure.

However, even with the above proposal, in order to obtain a porous material that does not contain gel-like silica, it is necessary to use per phase split glass II during acid elution to help elute the silica contained in the sodium borate phase. It was necessary to increase the amount of acid used, and in the case of thick-walled glass, it was not possible to completely prevent the precipitation of gel-like silica.

The present invention was made to solve these problems, and it is possible to produce a thick, high-silicate porous glass that does not contain gel-like silica and has sufficient pore volume and mechanical strength. In addition, the amount of acid required when producing these porous glasses can be reduced, and the method is suitable as a method for producing porous membranes for the purpose of separating substances from mixtures, concentrating, and reversing. It has the following.

That is, the invention of heavy chain 1 is 81 to 64% by weight%.
02.28-51% B2O3, 4.5-13% Na
Consisting of 2O and 3.5% or less L120, Ga Li
Producing a raw material glass consisting of a main component having a composition with a 2O/Na2O ratio of 0.5 or less and MoO3 in an amount of 2 to 13% by weight of this main component, without softening or deforming the raw material glass. It is characterized in that it is heat treated in a temperature range to separate (5) the alkali metal borate phase and the silica phase, and the alkali metal borate phase is eluted with an acid.

In addition, the invention of heavy chain 2 has an S 1 of 41 to 64% in terms of electric storage%.
02.28-51% B2O3,4-5-13% (
') A main component consisting of Na20 and L120 of 3.5% or less and having a L'20/Na20 ratio of 0.5 or less, and MoO3 of 2 to 13 weight i% of this main component,
and AlzOs, ZrO2 under the 10 gravimetric method
MgO2>-lattx liff.

At least one adjustment component selected from It is characterized by eluting the alkali metal boric acid salt phase with acid.

First, in the invention of votive material, raw glass is manufactured. This raw material glass has a weight i% of 41 to 64%08i02
．． 28-51% (D B2O3, 4, 5-13% Nm
Consisting of 2Q and 3.5% or less LizO, KatsuL
1gO/Na2O ratio is 0.5 Jl under f6.6 composition, and 2-13 g1i% (6
) Manufactured by mixing raw materials with MoO3 and melting in a conventional manner. When the total amount of 8102 il, 1 is less than 41% by weight, or when B2O3 exceeds 51% by weight, the silica phase cannot form a sufficiently strong network structure, and the resulting porous body mechanical strength becomes insufficient. When the amount of 5iOs+ exceeds 64% by weight, or when the amount of B2O3 is less than 28% by weight, the phase separation rate is too high, making it difficult to precisely control the pore diameter.

Furthermore, if the amount of Na2O is less than 4.5% by weight, significant elongation will occur during elution with acid, while if the amount of NagOO exceeds 13% by weight, significant shrinkage will occur during elution. Otherwise, the product will be damaged.

Furthermore, if the amount of L120 exceeds 3.5% by weight,
Alternatively, if the L20/N1120 ratio exceeds 0.5, phase separation will be excessively promoted, making precise control of the pore diameter difficult.

In particular, by adding Li2O in the above-mentioned range, the composition of the raw glass can be expanded to a lower N120 side than when only Na2O is included as the alkali.

If the amount of MoO3 added to the above-mentioned main components is less than 2%, the effect of MoO3 addition will be insufficient, and a porous glass that does not contain gelled silica will not be obtained. Also Mo
If the amount of O3 added exceeds 13% by weight, the phase separation rate will be too high, making it impossible to precisely control the pore diameter.

MoO3 added to the main component reduces the concentration of silica contained in the acid-soluble alkali metal borate phase during phase separation, and MoO3 itself also moves into the alkali metal borate phase, reducing acid elution. In some cases, it reacts with the silica in the alkali metal borate salt phase to form a soluble silicon molybdenum polymer, and by dissolving the silica component in an acid, it is prevented from precipitating as gel-like silica. At the same time, MoO3 also has the effect of increasing the volume fraction of the silica phase during phase separation and strengthening the fine structure.

Further, in the first invention, L added as a main component
Among the functions of Mo0a described above, 120 has the function of reducing the concentration of silica contained in the soluble phase during phase separation to prevent precipitation of gel-like silica, and the function of increasing the volume fraction of the 7-liquid phase to form a network structure. Further promotes reinforcing action.

Therefore, according to the invention #11, it is possible to easily produce a porous glass molded body that has excellent mechanical strength and does not contain gelled silica.

Next, in the first invention, after the raw glass produced as described above is molded, it is heat-treated in a temperature range that does not cause softening or deformation, and is separated into an alkali borate phase and a silica phase. .

Usually, the heat treatment temperature is 450 to 700℃, and the heat treatment time is 1 to 30℃ depending on the pore diameter of the porous glass.
It ranges from hours to several tens of days.

Generally, the longer the heat treatment time, the larger the pore diameter, so the pore diameter can be controlled as necessary.

If the heat treatment temperature is too high, the raw glass molded body will be deformed, its shape and dimensions will be distorted, and the glass will fuse, which is not preferable.

While avoiding softening and deformation of the raw glass molded body (9) In order to grow a phase-separated structure, the heat treatment temperature is gradually increased as the phase-separated structure develops, and the silica content of the alkali metal borate phase is reduced. For this stone to be sufficiently slow cooled and annealed.

As a result of such heat treatment, the raw material glass is phase-separated into an alkali metal borate phase and a silica phase, and these two phases are in a state where they are intricately entangled with each other.

Processes using water such as cutting and polishing are preferably carried out after heat treatment, since the altered layer formed on the processed surface may take on a structure different from that of the interior of the glass due to heat treatment, thereby interfering with acid elution.

Next, in the first invention, acid elution is performed to elute the alkali metal borate phase to obtain porous glass. Acid elution is preferably carried out using a 0.1-2N acid, usually sulfuric acid, hydrochloric acid, etc., at, for example, 60-100°C. The amount of acid per phase separation glass III is usually 30 ml or more.

Porous glass obtained by acid elution is generally made into a product by washing with water, drying, or, if necessary, undergoing surface treatment, heat treatment, processing, etc.

The pore diameter of the obtained porous glass is usually several tens to several thousand A.
Covers a wide range of areas.

Next, in the invention of heavy chain 2, in addition to the main component having the same composition as in the first invention and MOOB, at least one adjustment component selected from the group consisting of AJ20a t ZrO2 and MgO is added in an amount of 10 weight % of the main component. The following are added.

Since the raw material glass in the first invention contains Mo0a and L120, the phase separation tendency may become excessive, so such a conditioning component is used to control this and to suppress expansion and contraction during acid elution. Added to prevent damage.

&11 When the added violet exceeds 10% of the main ingredient,
The composition of the raw material glass may be damaged, causing devitrification or breakage during tR bath tB, or acid elution may become impossible. In addition, the manufacturing method of the invention of heavy chain 2 has the above 14%! The process is carried out in the same manner as in the first invention except for the addition of the ingredients.

As described above, according to the invention of heavy chain 1 and the second invention, L120 promotes the action of MoO3 and reduces the concentration of silica contained in the alkali metal borate phase during phase separation, thereby producing gel-like silica. Prevents precipitation in the pores of the porous body,
At the same time, the volume fraction of the silica phase is increased to strengthen the network structure.

As a result, a thick-walled borosilicate glass that does not contain gel-like silica and has excellent mechanical strength is obtained. In addition, if the glass is not particularly thick, a high silicate porous glass that does not contain gelled silica can be obtained by elution with a small amount of acid.

Because the resulting porous glass is highly silicic, it has particularly excellent chemical and thermal stability and can be used under harsh conditions such as in organic liquids, corrosive atmospheres, high temperatures, and high pressures. It is.

In addition, since the pore diameter can be controlled over a wide range of tens to thousands of amps, it is suitable for manufacturing plate-shaped, tubular, and capillary-shaped porous membranes for the purpose of separating, concentrating, and filtering substances. be.

Furthermore, in the invention of heavy chain 2, since an N alignment component is added, in addition to the above-mentioned effects, it is possible to control the tendency of phase separation, which tends to be excessive, and to further suppress expansion and contraction during acid elution.

Examples of the present invention will be described below.

Example 1 810255.8% by weight, B2O334.5%, N
1208.4%, L1203 1.3% as a main component, and 5.1% by weight of this main component as MOOB was heat treated at 500°C for 48 hours to separate the phases, and then crushed. A portion of 149 to 74 μm (100 to 200 meshes) was collected. 2 g of this glass was treated with 11 1N sulfuric acid at 95° C. for 2 hours to form a porous glass. The average pore diameter of this porous glass is 380 A,
The pore volume was 0.50 ml/i. Further, the specific surface area was a small value of 39 m''/11, indicating that gel-like silica was not included.

On the other hand, when the rod-shaped sample was measured for expansion and contraction during acid elution, it showed an elongation of 0.37%, and no breakage occurred during acid elution.

Example 2 (13) Two types of glass components having the compositions shown in the table below were prepared and each was melted.

This is a comparative example outside the scope of the present invention.

These glasses were heat-treated at 500°C for 48 hours to separate the phases, and then crushed to form 149-74 μm (100-
200 metsushiyu) was collected.

2 g of these samples were each treated with 1 N sulfuric acid at 9%
A porous glass was obtained by processing at 5° C. for 2 hours. The pore characteristics of these porous glasses are shown in the table.

In addition to having a very large pore volume of 0.95 ml/J/, sample 1 also has a larger pore diameter than sample 2.
It shows the effect of Li2O.

Furthermore, when sample 1 was measured for expansion and contraction during acid treatment, it was found that the expansion and contraction was 0.34%, and that a porous glass having sufficient mechanical strength could be obtained.

(14) (15) Contents of amendment Procedural amendment (voluntary) 1. Indication of the case Patent Application No. 38670 of 1988 2. Name of the invention Method for manufacturing porous glass 3. Person making the amendment Relationship to the case Patent Applicant Address: 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name
(114) Director of the Agency of Industrial Science and Technology Hirobe Yoda 4, Address of designated agent: 1-8-31-6 Midorigaoka, Ikeda City, Osaka Prefecture, Section 1 of “Detailed Description of the Invention” in the specification to be amended, page 13 of the specification Correct rL+203J in line 6 to rLi20J.

2. On page 15 of the specification, the following statement is added next to the table.

"Example 3 Weight test S i 02 46.0, B2O341.9, N
a2010.01Li202.1% of the main component, 7% by weight of the main component of MoO3, and 2 of the main component as an adjustment component.
500% M'go and 4% Zr0t glass.
It was heat-treated at ℃ for 48 hours to separate the phases, and then it was crushed and a portion of 149 to 74 μm (100 to 200 meshes) was collected. 2g of this glass was mixed with IQ's 1N hydrochloric acid,
Porous glass was obtained by elution at 95° C. for 2 hours. The average pore radius of this porous glass is 140, and the pore volume is 0.
66 m + lI/g, and the specific surface area was 103 m2/g. Further, when a rod-shaped sample was measured, an elongation of 0.13% was observed during acid elution, and no damage was observed. "(that's all)

Claims (1)

[Scope of Claims] 1 Consists of 41 to 64% 5102.2s to 51% B2O3, 4, 5 to 13% N120, and 3.5% or less L120, and has a Li2ω'NazO ratio of 0
．． A main component having a composition of 5 or less, and 2 of this main component.
A raw material glass consisting of ~13wt% MeO2 is produced, and this raw material glass is heat-treated in a temperature range that does not cause softening or deformation to separate into an alkali metal boric salt phase and a silica phase. A method for producing porous glass, comprising eluting an alkali metal salt phase with an acid. 2 41-64% 8102.28-51% B2O3, 4, 5-13% Na2Q and 3.5
It consists of 0LI20 or less, and Ll20/Na2
A main component whose O ratio is 0.5 or less, and 2 to 1 of this main component.
3% by weight of MeO2, and not more than 10% by weight of M2O3
, ZrO2, and at least one adjusting component selected from the group consisting of MgO, and the raw glass is heat-treated at a temperature range that does not cause softening or deformation to form an alkali metal borate phase and a silica phase. 1. A method for producing porous glass, which comprises separating the phases into two, and eluting the alkali metal borate phase with an acid.