RU2205793C1 - Light-transparent binding composition - Google Patents

Abstract

FIELD: fire-proofing materials. SUBSTANCE: light-transparent binding composition used in production of fire- proofing light-transparent glass blocks is prepared as follows. Colloidal potassium silicate solution containing 7-12% potassium oxide, 23-28% silica, and 50-70% water is prepared by partial depolymerization silica sol containing 15-45% silica with particle size no more than 30 nm affected by potassium hydroxide and/or potassium silicate with SiO₂/K₂O weight ratio below 2.5 until content of alpha-silica is 1 to 10% of the total silica content. Thus obtained solution is degassed, concentrated, and hardened. EFFECT: accelerated and simplified preparation procedure and avoided use of harmful inorganic materials. 3 cl, 3 tbl, 2 ex

Description

 The invention relates to the field of production of cementitious compositions, namely the manufacture of translucent cementitious compositions used in the manufacture of fireproof translucent glass blocks (OSS).

 Fireproof translucent glass blocks are multilayer products with a thickness of 10 to 30 mm or more, the supporting elements of which are sheets of glass, the gaps between which are filled with a translucent binder composition, forming a heat-insulating porous structure under the influence of high temperatures (in case of fire). Such glass blocks are intended for the manufacture of windows, transparent partitions and doors in warehouses, offices, and rooms with increased fire hazard. In the event of a fire, the OSS, in contrast to ordinary glass, counteracts an open flame, and prevents the penetration of smoke and thermal radiation for 30-90 minutes or more.

 Known translucent binder composition designed to fill the space between the sheets of glass fireproof glass block [[1] US 4873146, 32 V 09/00, 32 V 17/06, 09 K 21/00, op. 10/10/1989]. The composition consists of a solid hydrated alkali metal silicate containing 25-35% hydrated water, and at least one stabilizing agent representing a quaternary ammonium base. The composition foams (turns into a porous insulating material) when exposed to high temperatures due to the release of water vapor. A method of preparing a translucent binder composition is to dry an alkali metal silicate solution with the addition of a stabilizing agent directly on the glass sheets of the desired area. Subsequent gluing of these sheets together in an autoclave gives the finished OSS.

 The described method for preparing a translucent binder composition requires significant production areas and time-consuming during the drying operation, i.e. has poor performance.

 Another translucent composition is known, which is a hydrated alkali metal silicate with the addition of polyhydric alcohols and mono- or polysaccharides [WO 99/19421, C 09 K 21/02, B 32 V 17/06, op. 04/22/1999]. The additive content in this translucent composition is 5-22 wt.%, The molar ratio of silicon dioxide to alkali metal oxide in hydrated silicate should be more than 3.3. The method of obtaining the composition consists in drying an aqueous solution of alkali metal silicate together with the additive to a residual water content of 12-20% and grinding the resulting material into particles of 10-700 microns. For the manufacture of OSS, the powder is distributed on the surface of a glass sheet with a layer of 0.1-5 mm, a second glass sheet is applied on top and these operations are repeated until the product is obtained with the required number of layers of hydrated silicate. The product is autoclaved at a rather difficult temperature and pressure mode. Under these conditions, the hydrated alkali metal silicate turns into a continuous transparent layer fastening adjacent sheets of glass.

 The disadvantage of this composition lies in the complexity of its preparation and the need to use sufficiently sophisticated drying equipment and special autoclaves.

 According to another method (prototype [US 5565273, B 32 B 17/06, op. 15.10.1996]) OSS as a translucent filling contains a cured alkali metal polysilicate with a molar ratio of silicon dioxide to alkali metal oxide of more than 4 and a water content of up to 60% . A method of preparing a translucent composition consists in mixing an alkali metal silicate containing 44-60% water with a curing agent. A curing agent is a substance containing silicic acid, silicon dioxide, or capable of releasing silicic acid or silicon dioxide. Curing agents can also be organic and inorganic acids, esters, amides and other compounds of an acidic nature. This solution fills the space between the supporting elements (sheets of glass) of the OSS; after a certain time, the solution goes into a gel state.

 The effect achieved in the prototype method is the ability to produce a translucent composition to fill the OSS in a fairly simple and inexpensive way.

The disadvantages of the prototype method are:
1) its high sensitivity to the nature of the components and the conditions of their mixing; low reproducibility of results;
2) the duration of the preparation of the composition;
3) the toxicity declared in the prototype organic hardeners.

 Depending on the nature of the hardener and alkali metal silicate, as well as the method of mixing them, coagulation of the released free silicon dioxide occurs, which leads to a loss of transparency of the glass block. In addition, depending on the type of metal cation, the molar ratio of silicon dioxide to alkali metal oxide, the concentration of the solution and the characteristics of mixing the reagents, the mixture may initially form a viscous opaque mass, the clarification and liquefaction of which to a transparent mobile solution, which then forms a gel, can occur during several hours and even a day.

 The present invention allows to eliminate the limitations of the prototype method. It is possible to quickly obtain non-toxic transparent compositions for filling fire-resistant glass blocks that can foam at high temperatures.

The solution of this problem is achieved in that a colloidal solution of potassium silicate with a content, wt.%: K ₂ O 7-12, SiO ₂ 23-38, H ₂ O 50-70 is obtained by partial depolymerization of a silica sol with a concentration of SiO ₂ 15-45 wt % and particle size SiO ₂ not more than 30 nm with potassium hydroxide and / or potassium silicate with a ratio of SiO ₂ wt.% / K ₂ O wt.% less than 2.5 to a content of α-SiO ₂ 1-10 wt. % of the total SiO ₂ content, followed by degassing and concentration, and solidify.

Partial depolymerization here refers to the transition of SiO ₂ into a solution in the form of a low polymer form (the so-called α-SiO ₂ , [1]) from the surface of colloidal silica particles caused by the breaking of Si-O-Si bonds by the hydroxide ions of KOH and / or potassium silicate. Due to the physicochemical processes involved in the interaction of various forms of silica, after a certain time, the solution loses its original mobility with the formation of a translucent composition in the form of a gel.

The resulting translucent composition when heated above 100-150 ^o With swells in pairs of water contained in it.

 As in the prototype, the principle of using the proposed translucent binder composition in the production of OSS is to produce a frame consisting of two or more sheets of glass arranged in parallel and spaced from each other at a distance of 0.3-5 mm, filling the gaps between the sheets of glass with a colloidal solution of potassium silicate the above composition and its curing.

The technical effect achieved by the implementation of the present invention is to create a non-toxic translucent binder composition for OSS, which is a gel capable of foaming and forming a fine-meshed structure with low thermal conductivity when heated above 100 ^o C, as well as providing the ability to produce this composition quickly and reliably a method based on the use of inorganic materials that are safe for human health and not requiring large production areas and special orogostoyaschego equipment.

The content of α-SiO _{2 is} not an unambiguous function of the composition of the potassium silicate solution and depends on the nature of the starting components, their ratio and mixing method. To achieve the claimed technical effect, it is necessary that, with the specified composition of the composition, namely, when it contains, wt.%: K ₂ O 7-12, SiO ₂ 23-38, H ₂ O 50-70, the content of α-SiO ₂ was in the range of 1-10% of the total SiO ₂ content.

The composition and method of obtaining a binder composition for OSS, which is a solidified colloidal solution of potassium silicate of the above composition and obtained by partial depolymerization of a silica sol with a concentration of SiO _{2 of} 15-45 wt. % and particle size SiO ₂ not more than 30 nm potassium hydroxide and / or potassium silicate with a ratio of SiO ₂ wt.% / K ₂ O wt.% less than 2.5 to a content of α-SiO ₂ 1-10 wt. % of the total SiO ₂ content, followed by degassing and concentration, is a new, distinguishing feature of the invention.

 Currently, the proposed combination of features is not known from the prior art, and no solutions have been identified that have features that match the distinctive essential features of the proposed solution.

 The proposed solution cannot be inferred from the state of the art, since the physicochemical processes of gelation that occur in colloidal solutions of alkali metal silicates have not been thoroughly studied, and the result obtained in the present invention is unpredictable.

 The achievement of this effect is confirmed by the experimental data presented in Table 1.

As can be seen from table 1, the technical effect is achieved in those cases when at the same time all the parameters of the binder composition correspond to the range of declared values (cases B). The result is a fairly solid transparent gels, foaming with the formation of a fine-meshed structure when heated above 100 ^o C.

 The technical effect is not achieved (cases A and B in Table 1) when at least one composition parameter does not correspond to the range of declared values.

So, for example, when the content of SiO _{2 is} more than 38% or K ₂ O less than 7%, the gelation processes are significantly slowed down, the resulting gels do not foam, but mostly crack (cases A in Table 1). When the content of SiO ₂ less than 23% or K ₂ About more than 12% gels are not formed; colloidal solutions of potassium silicates retain a viscous flow (cases B in table 1).

Colloidal silica depolymerization is carried out by adding to it with stirring potassium hydroxide (in solid form or in the form of an aqueous solution) and / or potassium silicate with a ratio of SiO ₂ wt.% / K ₂ O wt.% Less than 2.5 (in the form of an aqueous solution or in the form solid hydrated form) to obtain a solution having the above composition. If the water content in the prepared solution exceeds 70%, bringing it to the desired composition is carried out by subsequent concentration.

Mixing the components, it is desirable to produce at such a speed that the temperature of the mixture did not rise above 40 ^o C.

The content of the low-polymer form of silica α-SiO _{2 is} estimated by the reaction of the prepared solutions with molybdenum acid by recording the amount and rate of formation of the yellow silicon-molybdenum complex [1].

The initial solutions of colloidal silica with particle sizes greater than 10 nm have a milky color or opalescence, i.e. are not transparent. We found that compositions prepared from initially opaque solutions of colloidal silica with particle sizes of less than 30 nm and a concentration of SiO _{2 of} 15-45% acquire transparency after some time, which is obviously due to the reduction of SiO ₂ particles to sizes less than 10 nm . However, when potassium silicates with a SiO ratio of ₂ wt.% / K ₂ O wt.% More than 2.5 are used as agents depolymerizing the silica sol, the milk color or opalescence of the resulting compositions can be preserved. Gels obtained from sols with particle sizes greater than 30 nm may also remain opaque.

 In a translucent binder composition filling the glass block, small gas bubbles can subsequently form, impairing the optical properties of the product.

To prevent the formation of gas bubbles in the gel, the prepared colloidal solutions of potassium silicate must be degassed by boiling under vacuum before curing. Lowering the pressure above the liquid allows the concentration of the gases dissolved in it to be reduced to values corresponding to solubility at steady pressure. Steam generated during boiling promotes more active removal of dissolved gases. If the water content in the prepared solution exceeds 70%, then at the same time as the degassing, the solution is concentrated, taking the resulting water vapor from the boiling zone to an H ₂ O content of 50-70%.

The gelation time of the solution is significantly reduced with an increase in its concentration and temperature. In this case, the increase in viscosity of the prepared solution begins long before it is completely hardened. It is necessary that it retains its initial mobility for at least 15-20 minutes from the date of preparation - i.e. for a time sufficient to fill one or more glass blocks. For this, degassing and concentration must be carried out during boiling in the temperature range of 20-45 ^o C. The boiling time at a temperature of 35-45 ^o C can be 5-15 minutes, boiling at 20-30 ^o C - 20-40 minutes. Potassium silicate solutions with an H ₂ O content of less than 70%, prepared taking into account the indicated parameters, remain stable (initial mobility) from several minutes to several tens of minutes - time sufficient to fill the OSS.

 The achievement of this effect is confirmed by the experimental data presented in Table 2.

From the examples of table 2 it can be seen that at temperatures above 45 ^o C in the gelation processes are accelerated, its survivability is sharply reduced. At a boiling point below 20 ^o With a fairly high probability of the formation of gas bubbles in the gel.

To turn the solution filling the glass block into a translucent binder composition filled with an OSS solution, it is necessary to maintain it at a temperature of 20-60 ^o C. To determine the time required for the complete gelation to complete, you can use the data given in Table 3.

As can be seen from table 3, at temperatures below 20 ^o With the gelation process is sharply slowed down; at a temperature of 70 ^o C and above, there is a probability of loss of transparency; the probability of this is especially high with prolonged heat exposure, necessary for heating sufficiently massive and significant in the thickness of the OSS; minor overheating also increase this probability.

 Examples of specific implementations of the invention.

As starting materials used: water sol of silica (TU 21-45-001-43811938-97) with a SiO ₂ content _of 26.6-30.8 wt.% And a particle size of SiO ₂ less than 10 nm; water sol of silica Levasil 100/45 with a content of SiO ₂ 45 wt. % and particle size 30 nm (manufacturer Bayer AG, Germany); potassium hydroxide (manufacturer "Chemapol", Czechoslovakia) with a basic substance content>84.5; an aqueous solution of potassium silicate Kasil 6 with a content, wt.%: SiO ₂ 26.5, K ₂ O 12.65 (manufacturer "PQ Corporation", USA).

 Example 1

Dry KOH is gradually added to 166 g of silica sol (TU 21-45-001-43811938-97) with stirring so that the temperature does not rise above 40 ^o C. Control over the content of α-SiO _{2 is} carried out according to the procedure [4]. When the content of α-SiO ₂ reaches 8.5%, the addition of KOH is stopped. The amount of alkali consumed was 16.6 g. The resulting solution was stirred for another 5 minutes, then evaporated by boiling (bp 40 ^{° C.} ) under vacuum for 15 minutes.

The prepared solution has the composition K ₂ O 9.5, SiO ₂ 30.5, H ₂ O 60.0. The solution is poured into the space between the glasses of the previously prepared glass block.

 The glass block is an assembly of five sheets of glass with a thickness of 4 mm and dimensions of 80x140 mm, located in parallel and spaced 1 mm apart. The assembly must be hermetically sealed on three sides, and one or two small holes are left on one side to fill the glass block with a solution of potassium silicate and remove expelled air. After filling the OSS with the binder composition, these openings are hermetically closed.

The curing of the solution is carried out by keeping the glass block at 60 ^o C for 2-3 hours

Fire tests of the OSS laboratory sample are carried out in a muffle furnace of the SNOL 1.6.2.5/11-M1 type. After heating the muffle furnace to 850 ^° C, an OSS sample is installed in place of the muffle door and then its state is monitored for 60 minutes.

 The foaming of the (first) layer closest to the heat source begins 1 minute after the start of the test, the second layer after 4 minutes, the third and fourth after 8 minutes. After 30 minutes, cracks appear on the outer glass, however, the glass remains intact due to the bonding action of the foamed aggregate. After 60 minutes, the appearance of the sample remains unchanged, the glass retains integrity.

 Example 2

An aqueous solution of potassium silicate Kasil 6 is gradually added to 50 g of a Levasil 100/45 silica sol with stirring, controlling the content of α-SiO ₂ according to the procedure [4]. When the content of α-SiO ₂ reaches 11.0%, the addition of potassium silicate solution is stopped. The amount of potassium silicate solution consumed was 140.0 g. Then, dry KOH was gradually added with stirring so that the temperature did not rise above 40 ^o C. Control over the content of α-SiO _{2 was} carried out according to the procedure [4]. When the content of α-SiO ₂ 6.5% is reached, the addition of KOH is stopped. The amount of alkali consumed was 1.5 g. The resulting solution was stirred for another 5 minutes, then subjected to degassing by boiling (bp 35 ^° C) under vacuum for 10 minutes.

The prepared solution has a composition of K ₂ O 11.5, SiO ₂ 35.5, H ₂ O 53.0.

 With the prepared solution proceed further in the same way as in example 1. Testing the laboratory sample of OSS for fire resistance leads to the same results as in example 1.

 The above examples do not exhaust all cases of application of the invention, but serve only as a demonstration of its implementation. In practice, other options can be used without violating the main idea of the proposed technical solution.

 Thus, the present invention solves the problem and ensures the achievement of the specified technical effect.

Sources of information
1. Korneev V.I., Danilov V.V. Soluble and liquid glass. St. Petersburg: Stroyizdat, 1996.216 s.

Claims (3)

1. Translucent binder composition comprising K ₂ O, SiO ₂ , N ₂ O, characterized in that the colloidal solution of potassium silicate with a content, wt.%: K ₂ O 7-12, SiO ₂ 23-38, N ₂ O 50 -70 is obtained by partial depolymerization of a silica sol with an initial concentration of SiO _{2 of} 15-45 wt.% And a particle size of SiO _{2 of} not more than 30 nm with potassium hydroxide and / or potassium silicate with a ratio of SiO ₂ wt. % / K ₂ About wt.% Less than 2.5 to a content of α-SiO ₂ 1-10 wt.% Of the total content of SiO ₂ , followed by degassing and concentration, and utverjdayut. 2. The composition according to claim 1, characterized in that the degassing and concentration of the partially depolymerized silica sol is carried out by boiling it under vacuum at 20-45 ^o C for 5-45 minutes 3. The composition according to claim 1, characterized in that the curing of the partially depolymerized Zola is carried out at 20-60 ^o C.

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