TRANSPARENT HEAT-PROTECTION ELEMENT

Abstract

A light-permeable heat protection element having a first and a second support member and having an intermediate layer between the first and the second support member. The intermediate layer has a cured alkali silicate gel formed of an aqueous alkali silicate solution and a silicon dioxide compound. The alkali silicate gel of the intermediate layer thereby has a molar ratio of silicon dioxide (SiO.sub.2 to alkali metal oxide (M.sub.2O) greater than 4. Furthermore, the alkali silicate gel has 0.05 to 0.14 weight percent of lithium silicate.

Claims

1. A transparent heat-protection element with a first and a second carrier element, comprising an interlayer between the first and the second carrier element, wherein the interlayer comprises a cured alkali silicate gel which is formed from an aqueous alkali silicate solution and from a silicon dioxide compound, wherein the alkali silicate gel has a molar ratio of silicon dioxide (SiO.sub.2) to alkali metal oxide (M.sub.2O) of larger than 4, wherein the alkali silicate gel comprises 0.05 to 0.14 percent by weight of lithium silicate.

2. The transparent heat-protection element according to claim 1, wherein the silicon dioxide compound comprises at least one of a silica sol, precipitation silicon dioxide, silicic gel and pyrogenic silicon dioxide.

3. The transparent heat-protection element according to claim 1, wherein the alkali silicate solution comprises at least one of a lithium silicate, a mixture of lithium silicate, sodium silicate and/or and potassium silicate.

4. The transparent heat-protection element according to claim 1, wherein the alkali metal oxide comprises a lithium oxide or a mixture of lithium oxide, sodium oxide and/or potassium oxide.

5. The transparent heat-protection element according to claim 1, wherein the interlayer comprises a means for reducing the freezing point of the water component.

6. The transparent heat-protection element according to claim 1, wherein the heat-protection element comprises an edge composite along the edges, between the first and the second carrier element, wherein the edge composite and the carrier elements form an intermediate space that is filled with the interlayer.

7. The transparent heat-protection element according to claim 6, wherein the edge composite comprises a spacer and a sealing mass.

8. The transparent heat-protection element according to claim 1, wherein a primer layer of a material whose adhesion onto the interlayer and/or onto at least one of the carrier elements reduces under fire-protection test conditions compared to room temperature conditions, is arranged between the first and the second carrier element.

9. The transparent heat-protection element according to claim 1, wherein at least one of the carrier elements is designed as a prestressed glass pane.

10. The transparent heat-protection element according to claim 1, wherein the heat-protection element comprises several interlayers that are arranged between two carrier elements in each case.

11. The transparent heat-protection element according to claim 1, wherein the heat-protection element is a fire-protection element.

12. A method for manufacturing a transparent heat-protection element according to claim 1, wherein, while using a hydrous alkali silicate, said hydrous alkali silicate being a mixture of the aqueous alkali silicate solution and of the silicon dioxide compound, is brought into an intermediate space between the first and the second carrier element, and is cured in the intermediate space into alkali silicate gel as an interlayer, wherein the molar ratio of silicon dioxide to alkali metal oxide is set to larger than 4 and the alkali silicate gel comprises 0.05 to 0.14% by weight of lithium silicate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The subject-matter of the invention is hereinafter described in more detail by way of preferred embodiment examples which are represented in the accompanying drawing. In each case are schematically represented:

[0037] FIG. 1 haze development in heat-protection elements over time, for different compositions of an interlayer in a fire-protection element, at 60° C.

DETAILED DESCRIPTION OF THE INVENTION

[0038] Basically, the same or analogous parts in the figure are provided with the same reference numerals.

[0039] FIG. 1 shows the haze development in heat-protection elements over time, in weeks, for different compositions of an interlayer in a fire-protection element, with storage at 60° C.

[0040] With long-term measurements of the haze of the heat-protection elements with two carrier elements and an interlayer of a cured alkali silicate gel with a constant molar ratio of silicon dioxide to alkali metal oxide (also indicated as the module), it has been found that the metering of lithium silicate to an essentially lithium-free alkali silicate has a positive effect on the long-term transparency of the intermediate layer. The effect of the reduction of the hazing can be attributed exclusively to the metered lithium silicate.

[0041] The heat-protection elements were aged at a constant temperature of 60° C. and their haze was measured over time, as shows in FIG. 1, in order to examine the ageing of heat-protection elements with different meterings of lithium silicate to an essentially lithium-free alkali silicate gel. A hazing can be initiated and very unfavourable environmental influences can be simulated with the help of such a long-term measurement.

[0042] The hazing of the heat-protection element can be specified as a percentage in haze (H). The scatter component of the transmitted light is determined by the haze value. Low haze values correspond to a high transparency and a high haze value entails a hazing of transparent elements.

[0043] The following examples serve for illustrating and explaining the invention and are not to be considered as limiting.

[0044] The following percentage details concerning the composition of the alkali silicate gel are to be understood as a percentage by weight and relate to the cured alkali silicate gel.

Example 1 Sample #1

[0045] 4.5% of monoethylene glycol (MEG) as an agent for reducing the freezing point was added to a hydrous, essentially lithium-free alkali silicate, as a mixture of 56% of an aqueous, essentially lithium-free alkali silicate solution and 39.5% of a precipitation silicon dioxide. The alkali silicate is an essentially pure potassium silicate, which can contain traces of sodium, but has no significant quantities of lithium. The module of the hydrous, essentially lithium-free alkali silicate was set to 5.09. The hydrous alkali silicate is brought into an intermediate space between a first and a second carrier element, said carrier element be designed in each case as a prestressed glass pane. The intermediate space is formed by the two parallel glass panes, and edge composite is formed along the edges of the glass panes. The hydrous, essentially lithium-free alkali silicate with a module of 5.09 and which is introduced into the intermediate space is cured in the intermediate space into an alkali silicate gel. The heat-protection element, which is manufactured in this manner, is known for example from WO 94/04355. The heat-protection element is subjected to a long-term measurement of the hazing at 60° C. The results of the long-term measurement are shown in FIG. 1. The readings of the sample #1, which are characterised by rhombuses (.diamond-solid.) show an increase in the hazing. The haze value is 11.3% after 21 weeks.

Example 2-Sample #2

[0046] In a modified variant, a hydrous, essentially lithium-free alkali silicate according to Example 1 was used, to which however 0.1% (percentage by weight, with respect to the cured alkali silicate gel) of a lithium silicate solution with 2.65% lithium oxide was metered. The module of the hydrous, lithium-containing alkali silicate was set to 5.09, as with Example 1, and all other parameters remain unchanged vis-à-vis Example 1. The respective heat-protection layer was likewise subjected to a long-term measurement of the hazing at 60° C. The results of the long-term measurement are shown in FIG. 1. The readings of the sample #2, which are characterised by squares (.square-solid.), show an increase in the hazing. The haze value after 21 weeks is only 8.4% in comparison to sample #1.

Example 3-Sample #3

[0047] In a varying embodiment, a hydrous, essentially lithium-free alkali silicate according to Example 1 (sample #1) was used, to which however 0.2% of the lithium silicate solution with 2.65% lithium dioxide was metered, similarly to Example 2 (sample #2). The module of the hydrous alkali silicate was set to 5.09, as in Example 1 and 2, and all other parameters remain unchanged vis-à-vis Example 1. The respective heat-protection element was likewise subjected to a long-term measurement of the hazing at 60° C. The results of the long-term measurement are shown in FIG. 1. The readings of sample #3, which are characterised by triangles (.box-tangle-solidup.), show a minimal increase in the hazing. The haze value was only 2.6% after 21 weeks.

Example 4-Sample #4

[0048] In a varying embodiment, a hydrous alkali silicate according to Example 3 (sample #3) was used, to which however 0.5% of the lithium silicate solution with 2.65% lithium oxide was metered. The module of the hydrous alkali silicate, as in Example 1, 2 and 3, was set to 5.09, and all other parameters remain unchanged vis-à-vis Example 1. The respective heat-protection element was likewise subjected to a long-term measurement of the hazing at 60° C. The results of the long-term measurement are shown in FIG. 1. The readings of the sample #4, which are characterised by circles (), show a minimal increase in the hazing. The haze value is only 3.8% after 21 weeks.

[0049] Overview. The module and the water content of the samples #2-#4 are set to 5.09 and 42% respectively, as with the sample #1. With sample #2, 0.1% (percent by weight) of a lithium silicate solution is metered to an essentially lithium-free alkali silicate. Moreover, with sample #3 0.2% and with sample #4 0.5% of lithium silicate solution are metered to an essentially lithium-free alkali silicate.

[0050] The aforementioned compositions for alkali silicate gel are used as an interlayer for the respective heat-protection elements (#1-#4), with which the alkali silicate gel is arranged between a first and a second carrier element of glass. The samples #1-#4 are each subjected to a long-term measurement of the hazing tendency. The temporal course of the hazing at 60° C. and corresponding to the sample numbers (#1 to #4) and compositions is shown in FIG. 1. The respective measurement points are represented by rhomboid for sample #1, by squares for sample #2, by triangles for sample #3 and by circles for sample #4.

[0051] The percentage details concerning the composition of the alkali silicate gel of the interlayer relate to the percentage by weight with regard to the total mass of the intermediate layer.

[0052] It is clearly evident from FIG. 1 that a metering of lithium silicate to an essentially lithium-free alkaline silicate in small quantities (see for example sample #2) effects a reduction in the hazing. A significantly more pronounced reduction in the hazing can be effected by a further inventive metering of lithium silicate (see sample #3 and #4 in FIG. 1). As is evident from FIG. 1, the haze value after 21 weeks for sample #1 is 11.3%, for sample #2 with a low metering of lithium silicate already only 8.4%, for sample #3 only 2.6% and for sample #4 with a greater metering 3.8%. It is therefore clear that an over-metering of lithium silicate can surprisingly lead to a renewed increase of the haze value.

[0053] The long-term measurements of the haze of the heat protection elements, as shown in FIG. 1 show that an increased reduction of the hazing of the heat-protection element as an appearance of ageing can be achieved in the range of 0.05 to 0.14 percent by weight of lithium silicate (samples #3 and #4). A renewed increase of the hazing over the course of time can be ascertained with a higher content of lithium silicate. In other words: an over-metering or under-metering of lithium silicate to alkali silicate gel leads to no or only a lesser pronounced positive effect on the ageing resistance of the heat-protection element.

[0054] The alkali silicate gel of the interlayer can include 54% to 59% of aqueous hydrous alkali silicate solution and 35% to 42% of a silicon dioxide compound as well as 0.05% to 0.14% of lithium silicate, for the heat-protection element according to the invention.