CS231858B1 - Basic borosilicate glass for production of microporous glass - Google Patents

Description

The subject of the invention is a borosilicate base glass for the production of microporous glass having a pore size of 5 to 350 nm.

Microporous glasses have a variety of uses, particularly as catalyst supports, molecular sieves, special membranes, chromatographic materials and as substrates for enzyme immobilization. The applicability of microporous glasses for a particular purpose depends largely on the pore size. For example, for use in biochemistry, a pore size above 5 nm is required due to the high molecular weight of the substances used.

The principle of microporous glass production consists in heat treatment of the base glass in the temperature range of 400 to 900 ° C for the time required to achieve the desired degree of glass separation, followed by leaching of the glass with an acid solution or possibly an alkaline hydroxide solution.

The heat treatment time of the base glass increases with the pore size of the resulting microporous glass, and can be up to hundreds of hours if large pores are required.

It is known that the application of higher heat treatment temperatures can reduce the heat treatment time required.

For example, according to U.S. Pat. No. 3,758,284, a glass of simple Na ₂ OB ₂ O ₃ -SiO ₂ with a 610 ° C heat treatment for 24 hours achieves a final pore size of 50 nm. For the resulting pore size of 170 nm, according to the same patent, a time of about 42 hours at 700 ° C or 90 hours at 660 ° C is required.

If the required pore size is even greater, the heat treatment time required at these relatively high temperatures is considerably extended.

The technological process of microporous glass production can also be influenced by the use of a suitable glass base glass. Most of the known panes or strains are based on the Na ₂ OB ₂ O ₃ -SiO _{2 system} .

Other components include alkali metal, rare earth metal oxides, etc.

E.g. čs. No. 133,302 discloses potassium oxide K ₂ for ultraporous glass having a molecular sieve of 0.5 nm.

According to MS. U.S. Pat. No. 132,895 discloses alumina Al 2 O 4, fluorine F _2, and manganese oxide MnO as further components of soda-borosilicate glass. The specific surface area of the glass is about 730 m @ 2 / g, which corresponds to a pore size of about 1 to 3 nm, and the glass has good thermal stability and acid resistance.

However, in the prior art glasses, especially when trying to achieve the largest pore size in microporous glasses, long heat treatment times occur at relatively high temperatures. There is also a risk of undesired crystallization of the base glass, possibly even deformation of the product.

The mentioned disadvantages are removed or substantially reduced in the basic glass composition of the invention which contains a concentration by weight from 55 to 75% of silica SiO _2, 18-35% boron oxide B ₂ O ₃ 3-17%, singly or in combination of sodium oxide Na ₂ 0, potassium K ₂ 0, lithium Li ₂ 0, ^and 0.2 to 5% phosphorus pentoxide P2 ° 5 ^{and 0.2 to 5%} fluorine F2 ·

Preferably, the base glass may also contain alumina Al ₂ O ₃ in a concentration up to 3% by weight.

The simultaneous occurrence of P ₂ O 3 and fluorine F ₂ in the presence of the other components in the range given in the base glass allows a reduction in the heat treatment time at relatively lower necessary temperatures compared to the prior art microporous glass preparation processes. This beneficial effect can be attributed to the interaction of the combination of P ₂ Og and fluorine F ₂ with the other glass components, resulting in a reduction in the glass surface tension while reducing the solubility of the scavenging phase in the heat treatment temperature range. Effect of combination of phosphorus pentoxide P ₂ 0 _s ^{and fluorine} F ₂ is significantly more pronounced than can be expected only from the influence on the process components themselves segregation.

This makes it possible to achieve the desired degree of separation at a lower heat treatment temperature and, as a consequence, the favorable effect described above. Said effect of the invention is particularly pronounced in the production of microporous glasses with pore sizes above 100 nm.

The alumina ^{in the} base glass can reduce the corrosion of the refractory material and also favorably influence the leaching process of the base glass.

The effect of the invention results from the following examples, in which the percentages are by weight.

Example 1 Example 2 SiO ₂ 64.2 % 64.8 '% boron oxide B ₂ O ₂ 25.0 % 25.5 % sodium oxide Na ₂ 0 7.3 % 5.9 % potassium oxide K ₂ 0 1.5 % phosphorus trioxide P ₂ ° 5 1.5 % 1.0 % fluorine 1? 2 2,0 % 0.5 % Alumina Al ₃ O ₃ 0.8 % heat treatment: temperature / ° C / 610 610 time / h / 24 21 pore size (nm) 225 75

.Example .3 .......... Example .4

silica S10 ₂ 63.1% 65.8% boron oxide B ₂ O ₂  24.5% 24.0% sodium oxide Na ₂ 0 7.0% 6,7% potassium oxide K ₂ o lithium oxide Li ₂ 0 0.5% P ₂ O 3 0.2% 0.5% fluorine F, 4.7% 3.0% heat treatment: temperature / ° C / 613 550 602 650 time / h / 24 24 24 48 . pore size ./nm / ..... . . .180 ....... ...... 43 .9.7. . 27.0

Microporous glass can be prepared from the glass according to the invention in the form of pulp, as it is the most common so far, but also in the form of rods, tubes and plates, which can easily obtain pore sizes above 150 nm.

Claims (2)

SUBJECT OF THE INVENTION 1. Borosilicate glass for the production of microporous glass of pore size 5-350 nu, characterized in that it contains in a concentration of 55 to 75% of silica SiO, 18-35% boron oxide BjOj, 3-17% sodium oxide Na ₂ 0 and / or potassium kyo and / or lithium Li ₂ 0 and from 0.2 to 5% phosphorus pentoxide P ₂ O ^{and from 2} to 5% fluorine F 1. 2. Basic glass according to claim 1, characterized in that aluminum oxide ⁱⁿ H 2 ^O 3 has a weight concentration of trace -5%.