SE505978C2 - Transparent, fire resistant glazing panel - Google Patents

Abstract

Transparent, fire-resistant, glazing panels comprise at least one layer of intumescent material (3) bonded to at least one structural ply (1, 2) of the panel. Such a panel comprises a structural ply which is bonded to an intumescent layer, which has been formed by compacting grains of an intumescent hydrated metal salt, and which has a total water content in the range 20 to 26% inclusive. This promotes the retention of good optical properties despite ageing. Such a panel may be manufactured by a method in which grains of an intumescent hydrated metal salt having a total water content of between 22% and 26% by weight are distributed as a layer on a surface of a ply to be incorporated into the panel, and in which, while the layer of grains is sandwiched between a pair of moulding plates, that layer is subjected to heat and pressure conditions to degas and compact it and cause it to become bonded to that surface of the ply of the panel. That ply and one moulding plate may be one and the same, and the second moulding plate may also go to form a ply of the panel. <IMAGE>

Description

15 20 25 30 35 2 "Some transparent and light-transmissive glazed assemblies can meet the requirements for stability and integrity (RE) and in some cases insulation (REI, where R stands for" resistance ", E for" tightness "and I for "insulation").

"The possibility of direct fire propagation through openings caused by glass rupture should only be considered for fire protection measures: it may also be necessary to take into account the heat transmitted through the vitrified assembly, which may still be intact, as such heat may cause ignition. of combustible materials.

"Glazed mounting fire resistance according to class RE under the fire conditions defined in ISO 834 provides for a given time, stability and integrity.

The temperature on the unexposed side has not been taken into account.

"Glazed mounting, fire resistant according to class REI under the fire conditions defined in ISO 834 provides for a given time, stability, integrity and insulation".

There are different degrees of fire-resistant panels and among those that are generally recognized are degrees that correspond to panels that are effective barriers against flames and smoke (ie class RE) during time periods of 15, 30, 45, 60, 90 and 120 minutes.

Other grades correspond to panels that are effective barriers to the passage of flames and smoke and also have certain insulating properties (ie class REI) again during time periods of eg 15, 30, 45, 60, 90 and 120 minutes.

The insulating properties that a panel must offer to meet the standard REI level are short that no point on the surface, which is exposed to the outside of the oven, may be exposed to an increase in temperature of more than 180 ° C above its initial (ambient) temperature and the average temperature increase on the 10 15 20 25 30 35 l '“o Sfis gflv 3 surface must not exceed 140 ° C. Such panels belonging to class REI can also form barriers to the transmission of infrared radiation from the fire hearth.

It is extremely important that the layer of intumescent material in such a panel should have good fire-resistant properties during a fire process and also that it should retain acceptable optical properties until it begins to swell during the course of a fire.

Hydrated metal salts, such as metal silicates, especially alkali metal silicates, have been used in the manufacture of such panels for a number of years. Representatively, the layers included in the finished panels have a water content of between 29 and 35%. Here and elsewhere in this specification, references to water content are references to water content as a part by weight of the intumescent material used to form the layer or as a part by weight of the intumescent material included as a layer in the finished panel (before eruption). of a fire and concomitant modification of that layer). During a fire, the hydration water is driven by the heat of the fire and the layer of intumescent material is converted into an opaque foam, which serves as a barrier to both radiated and conducted heat and that layer can also serve to bind construction panels in the panel such as glass sheets, which can become fragmented by thermal shock due to fire. The efficiency of the panel as a barrier against the passage of flames and smoke is thus also extended.

The effectiveness of a panel of hitherto known type as a fire screen depends on several factors. The efficiency of a laminate consisting of a single layer of a given intumescent material interposed between two glass sheets of a given thickness increases with the thickness of the intumescent layer. For a previously known panel with a given mass per unit area, ie for the same total thicknesses of glass and intumescent material, the efficiency of such a known panel can be increased by forming it as a five-layer laminate in which there are two intumescent layers held between three glass sheets . Thus, a laminate 10 15 20 25 30 35 505 9 "" "8 4 of three glass sheets each 4 mm thick with two intumescent layers each 1 mm thick between them has often been found to be more effective than a laminate of two 6 mm glass sheets about a single intumescent layer 2 mm thick. An equal efficiency can therefore be achieved by using a thinner panel comprising several layers. It is clearly desirable to provide highly effective fire resistant panels, which have a low mass per unit area but forming four or more layer panels can be expensive.

Another problem associated with the use of hydrated metal salt layers as intumescent material is the aging of the material over time. This aging is evident as a deterioration of the optical properties of the panel, such as a decrease in the transparency of the hydrated intumescent material, which in turn lowers the transparency of the panel. Such a deterioration in the characteristics of a panel will clearly be to the detriment of its use.

The problem of deterioration of the optical properties in the aging of a fire-resistant panel, in which an intumescent layer is included, has been known for many years and various attempts have been made to solve this problem. A major cause of the deterioration in optical properties has been the appearance of microbubbles in or near the surface of the layer and it is known to build up the layer by drying in situ a solution of the hydrated metal salt using water which has been degassed and to be be careful when preparing the solution not to stir the solution to such an extent that air or other gas is redissolved, so that it can reappear as the dried layer ages. While this provides an improvement in the aging properties of the panel, it is not entirely satisfactory if such a panel is to be used in circumstances where it is exposed to mild heat, for example due to direct sunlight. It is also known to add a stabilizing agent to the hydrated metal salt, such as a partially dissociated nitrogen-containing organic compound, for example a quaternary ammonium compound, such as tetramethylammonium hydroxide and this really gives better results.

It is an object of the present invention to provide a transparent fire-resistant panel which exhibits good aging properties, which does not substantially depend on the use of such an additive and which also offers good fire-resistant properties during a fire process.

According to the present invention, there is provided a transparent, fire-resistant glazing panel comprising at least one layer of intumescent material, bonded to at least one construction layer in the panel and characterized in that the panel comprises such a construction layer which is bonded to the intumescent layer, wherein a such a layer is formed by compressing grains of an intumescent hydrated metal salt and which layer has a total water content in the range 20-26%. We have found that such a panel is less susceptible to deterioration of its optical properties over time than a known panel is, in which the water content is slightly higher. In fact, the aging properties of a panel according to this invention are, under otherwise equal conditions, better than those of a panel whose intumescent material has a higher water content in the range of 29-34% and which includes a stabilizing agent such as tetramethylammonium hydroxide. This is quite surprising and it is not at all clear to us why this favorable result would arise by using an intumescent layer with a lower water content.

It is also surprising that such a panel may have improved fire-resistant properties, since one would have expected that the lower water content in the intumescent layer would actually reduce the efficiency of the panel because there would be less foaming during a fire process.

In fact, we have found that a three-layer laminate in which a single intumescent layer is interposed between a pair of vitreous sheets in accordance with the present invention tends to have better fire resistance than a three-layer laminate of similar dimensions, whose intumescent layer has a higher 30 35 _2505 978 6 water content. Thus, the invention offers the further advantage of enabling the same fire resistance to be achieved by using a thinner and lighter panel without thereby incurring further complications and cost to increase the number of layers in the laminate.

Furthermore, the rather low water content of the intumescent layer, a maximum of 26%, promotes its hardness so that it is more physically stable and has less tendency to creep.

Working in such a way so as to produce a layer with a water content of not less than 20% is advantageous for producing panels with good transparency.

It is preferred that the layer has a water content of not less than 22%. The presence of such water particles in the intumescent layer offers very good foaming properties during a fire process and they also allow the formation of a hard and compact layer of intumescent material, which retains good optical properties over time. Optimally, the layer has a total water content of not less than 23%.

For best results, it is also preferred that the layer have a total water content of not more than 25%, as this promotes the maintenance of good optical properties despite the aging of the panel.

Such a layer of grains can be easily compressed by subjecting it to suitable conditions of temperature and pressure to form a layer in which the individual grains are not visible to the unarmed eye, so that the layer offers a uniform appearance and is transmissive. parent. However, the presence of such grains can be detected, for example by ultrasound or by microscopic examination, and thus the grain boundaries, although invisible, are assumed to remain within the layer. It is believed that this structure on the layer may have some effect on the behavior of the intumescent material during a fire process and perhaps also on the properties of the layer before such a fire. A possible contributing factor to the panel's potential improved fire resistance according to the invention is that although the grain boundaries disappear for the unarmed eye, they may remain and act as a plurality of bubbles for formation at the unarmed eye. the reaction of the intumescent material during a fire process, which thus results in a fine-foamed structure which has a good and uniform insulating effect over the area of the panel.

Advantageously, the grains have a maximum dimension of less than 700 μm and they preferably have a size above 10 μm and, for example, they can have a maximum dimension of between 150 and 500 μm. This promotes the ease with which the grains can be formed into a compact layer and it can also have a beneficial effect on the behavior of the intumescent material during a fire. Panels incorporating this preferred feature of the invention have been found to provide a fine and uniform foam structure when exposed to intense heat as would be provided by a fire. This is assumed to be at least mainly due to the relatively low water content of the intumescent material compared to that used hitherto in the manufacture of fire-resistant panels and the fact that there is a residual grain in the compacted layer, but the fineness of the remaining grain - the structure of the layer can also be a contributing factor.

As stated, the effectiveness of a fire resistant panel during a fire depends at least in part on the thickness of the layer or each layer of intumescent material. It is preferred that the layer or such layer of intumescent material has a thickness of between 0.1 and 5.0 mm. Layers even as thin as 0.1 mm can provide sufficient short-term protection against fire, although of course better protection is provided by thicker layers. In general, an increase in the thickness of such a layer beyond 5 mm does not give a proportional increase in the degree of protection provided and we have also found that it is also more difficult to form thicker compact layers which exhibit good optical properties.

The intumescent material may be any of a large number of hydrated metal salts, although the use of an alkali metal salt is preferred. Examples of suitable alkali metal salts which can be used in hydrated form are as follows: potassium aluminate, potassium plumbate, potassium stannate, sodium stannate, sodium aluminum sulphate, potassium aluminum sulphate, sodium borate, potassium borate, potassium orthophilicates and sodium orthophilicates. However, for cost and efficiency reasons, it is preferred that the intumescent material comprise hydrated sodium silicate, which may optionally be mixed with hydrated potassium silicate.

Preferably, the panel comprises two structural layers laminated together via an intumescent layer as previously mentioned. This is a very stable and simple panel construction. In its simplest form, such a laminate could consist of glazing materials, which are bonded directly to each side of an intumescent layer, or where a higher degree of fire protection is desired, two intumescent layers can be bonded to form a laminated panel, with three construction layers of glazing material. It will be readily appreciated that if a higher degree of fire protection is required, two or more such panels would themselves be laminated together, for example by using intermediate adhesives such as polyvinyl butyral in a process known per se in the laminated glazing art.

We have already mentioned that the aging properties of a panel according to the present invention are in otherwise equal conditions, better than those of a panel whose intumescent material has a higher water content in the range 29-34% and which includes a stabilizing agent. It would be natural, therefore, to consider that there would be no incentive to use such a stabilizer in a panel whose intumescent materials exhibited low humidity according to the invention, since such a panel already has very good aging properties. However, the use of such a stabilizing agent can give a further improvement in a panel according to the invention aging properties and furthermore it can have another and completely unexpected advantage in that the use of such an agent can promote the fire-resistant properties of the layer during a fire and this is of particular advantage in a panel having a plurality of layers of intumescent material incorporating such an additive. It is preferred that such a layer of intumescent material contains at least one silicate stabilizing agent.

Preferably, the silicate stabilizing agent comprises at least one nitrogen-containing organic compound, for example an amino compound which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide.

We believe that the inclusion of a stabilizing agent such as tetramethylammonium hydroxide in accordance with these preferred features of the invention not only provides an additional advantage in terms of the properties of the panel in aging, but may also have a beneficial effect on the foam produced during a fire. and so contribute to the panel's fire resistance efficiency.

A panel according to the invention can be manufactured very simply and comprises at least one layer of intumescent material bonded to at least one construction layer in the panel, where grains of an intumescent hydrated metal salt with a total water content of between 22 and 26% by weight are distributed as one layer. on a surface of a layer to be included in the panel and while the layer of grains is laid between a pair of forming sheets, the layer is subjected to heat and pressure conditions to degas and compact it and cause it to bond to the layer surface of the panel.

The panel is very simple to manufacture and in this case devices already known in the art in the lamination glazing technique can be used.

In addition to imparting very good properties in terms of aging and fire resistance of the panel, the choice of intumescent grains with the specified moisture content has other advantages.

The use of intumescent grains with a water content not exceeding 26% promotes excellent retention of the optical properties of the panel despite its aging and such grains are also easy to handle before and during the manufacture of the panel. Intumescent grains with a water content not less than 22% are quite easy to compact into hard and transparent layers or at least into layers which will be transparent when bonded between a pair transparent discs.

This does not necessarily mean that the resulting intumescent layer will necessarily have a water content of 22% or higher. Some moisture is likely to be drawn off during degassing, but the average water content in the layer will only be very small below the average water content in the grains from which the layer was formed. We have found that the difference in water content between the grains and the layer is at most 2% and can be negligible, so that for example a layer formed of grains with an average water content of 25% will have an average water content of between 23 and 25%. Where lower humidity grains are used to form the layer, it is highly desirable to control the degassing conditions so that only a small amount of water is drawn off: it is undesirable to have an average water content in the layer which is below 20% and most preferred is that such water content is not below 22%.

During degassing and compaction, the intumescent layer becomes bonded to the panel layer, with which it is in contact. That layer may be a film of thermoplastic adhesive material for subsequent bonding to construction layers in the panel, such as a sheet of glass, but if this is not particularly desired for any particular reason, it adds an extra step in the manufacture and it is thus preferred that the layer of barley is distributed on a surface of a glassy disc, which will be included in the panel and which also constitutes a forming plate of said kind. If it is desired that the second forming plate should not be bonded to the resulting intumescent layer, that plate may be treated in a suitable manner, for example with a silicone, but it is preferred that the second forming plate be made of or clad with a layer which will to be included in the panel and to which the intumescent layer becomes bonded. The intumescent layer can thus be laid between two layers of the panel, which is formed into a laminate at the same time as the layer is degassed and compacted. The entire panel can indeed be mounted and formed into a laminate by the degassing and compaction treatment. The panel can then be transferred to an atuoclave for subsequent high pressure bonding steps if required.

It will be appreciated that any desired number of successive alternating layers of vitrified material and intumescent material may be laminated together in that manner, but that the difficulty of making a laminate having good optical properties increases with the number of layers of intumescent material, especially if three or more several such layers are to be compacted simultaneously and if the sandwich assembly will be subjected to heating during compaction and / or bonding of such layers as will be discussed below.

It will also be appreciated that two or more such panels consisting of alternating layers of vitrification material and intumescent material may themselves be laminated together using adhesive thermoplastic film material, if greater fire resistance is required. Such a method has practical advantages where it is desired to include several layers of intumescent material.

As a practical example, it may be desirable to produce a fire-resistant panel with four layers of intumescent material, each about 1.5 mm thick. We have found that layers of grains of intumescent material to form such compacted layers need to be up to about seven times as thick as the compacted layers so that in practical terms such a panel can shrink in thickness by up to about 36 mm during degassing and binding. Manufacturing is simplified by forming two panels each having two such intumescent layers and laminating the panels together using a thermoplastic adhesive film material, such as polyvinyl butyral. The presence of such a thermoplastic adhesive film material can also have a beneficial effect on the fire resistance properties of the panel by limiting the propagation of cracks due to thermal shock. In the most preferred embodiments of the invention, the grains have a total water content of not less than 23% and preferably such a water content amounts to not more than 25% by weight. The presence of such water components in the intumescent grains gives the resulting layer very good foaming properties during a fire, and also allows the formation of a hard and compact layer of intumescent material, which possesses and maintains good optical properties over time.

Preferably, the grains are dimensioned so that at least 90% by weight of them have a maximum dimension of less than 700 μm and preferably in the range 150-500 μm. Grains of such sizes are suitable for handling and they impart to the resulting compacted layer its structure, which is believed to be favorable to give good fire-resistant properties as has been stated. Such grain sizes are also particularly suitable for forming layers of the thicknesses specifically intended, for example layers formed to a thickness of between 0.1 and 5.0 mm.

For at least part of the time during degassing and bonding, the layer of intumescent material is advantageously exposed to a temperature of at least 80 ° C. Heating the intumescent material to such a temperature promotes degassing and compaction and also bonding to a layer in the panel. It is understood that the intumescent material must not be exposed to such high temperatures which, taking into account the pressure applied to the material, would give rise to premature foaming of the intumescent material. It can be noted here that it is much easier to ensure that a single intumescent layer or each of two intumescent layers in a panel is subjected to the optimal heating pattern than it is to ensure that each of three or more layers is optimally heated if only due to that the central layer (s) will be more shielded from the heat source by other layers in the panel than the outer layers are.

During degassing and bonding, the layer is subjected to intumescent material, advantageously for a pressure of less than 30 kPa. 10 15 20 25 30 35 505 97'8 13 This allows excellent degassing of the intumescent material.

We have previously mentioned the use of additives in an intumescent layer to improve its aging properties.

The use of such an additive may have other unexpected benefits by promoting fire resistance during a fire as also mentioned. Therefore, such intumescent material advantageously contains at least one silicate stabilizing agent and preferably the silicate stabilizing agent comprises at least one nitrogen-containing organic compound, for example an amino compound which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows a schematic view of a device for degassing and compacting a layer of intumescent material in a method of manufacturing a panel according to the invention. panel built up consisting of two sheets of glass 1, 2 and an intermediate layer 3 composed of grains of intumescent material with a total water content of between 22 and 26%. The grains are of a grain size fraction, which passes through a sieve with sieve openings of 500 μm, but which is retained by a sieve with sieve openings of 150 μm. The grains are simply spread loosely on a first sheet of glass and leveled with a grain layer thickness of seven times the desired final thickness of the compacted layer to be formed.

The sandwich panel is enclosed within a housing 4. The housing is connected by means of a vacuum line 5 to a pump 6 through which subatmospheric pressure can be maintained within the housing to keep the space between the discs 1, 2 exposed to suction.

When the pump is put into operation, the upper and lower walls of the housing are pulled towards the main outer surfaces of the enclosed sandwich assembly and the glass sheets 1, 2 act as forming plates to compact the granular intumescent layer 3. The housing is at least in its peripheral zone 7, sufficiently rigid to resist collapse against the edges of the sandwich assembly, so that a space 8 at a subatmospheric pressure is maintained by the pump 6 and maintained within the housing 4, around the edges of the sandwich laminate 1, 2, 3 .

The use of a housing enclosing the sandwich assembly offers the advantage that the size of the housing relative to the dimension of the sandwich assembly is not critical. The cover can easily be applied to sandwich mounting in different size ranges.

Furthermore, the use of such a housing facilitates the application of uniform pressure over the entire area of the main surfaces of the sandwich assembly during its treatment, so that reaction forces arising from pressure differences between the environment in which the housing is located and the space within the housing will not be such as to cause bending of the outer discs 1, 2 in the sandwich assembly. Such bending could lead to the formation of bubbles in the edges of the layer 3 and can also lead to a non-planar end product.

In a variant of the device just described, optional clamping devices are provided to absorb reaction forces arising from pressure differences between the inner and outer of the housing 4. In Fig. 1 such clamping devices are shown as a pair of frames 9 of the same shape but slightly larger than sandwiches. the assemblies 1, 2, 3, which are kept at a distance from each other by a plurality of pillars such as 10. The frames 9 are so arranged at a distance from each other through the pillars 10 to keep the casing slightly away from the edges of the assembly, when the intume - the scenta layer has shrunk in thickness to its final compacted dimension, shown in the drawing.

Heating devices (not shown) may be provided over the upper and lower surfaces of the housing 4 to heat the intermediate intumescent material 3 to assist in the compaction and bonding of the sandwich assembly.

A sandwich assembly can be handled by the suction devices shown in Fig. 1 in a simple manner, where the exterior of the housing 4 is always exposed to atmospheric pressure. in an example of the method 10 15 20 25 30 35 505 978 15 the pump 6 is switched on to reduce the pressure within the housing, i.e. the pressure acting on the edges of the assembly in the edge space 8, to a value below 30 kPa. The exact optimum value will depend on the water content of the intumescent grains used. The required value can be reached after a few minutes and it is maintained for another 100 minutes.

The sandwich assembly is initially at room temperature (20 ° C). The sandwich assembly in the housing 4 is heated so that it reaches a temperature of 90 ° C after 4-5 minutes.

After the required degassing, the pressure in the casing is allowed to return to atmospheric pressure for a period of about 15 minutes. At the end of this time, a granular layer 3 is found to have been compacted to such an extent that the boundaries between the grains have become invisible to the unarmed eye and the sandwich assembly is found to have bonded together as a transparent laminated panel. Of course, this panel can then be transferred to an autoclave for subsequent high pressure bonding steps, if desired.

Water loss from the intumescent material due to extraction during its compaction to the layer is found to be less than 2% in relation to the weight of the layer.

EXAMPLE 1 A series of panels were made by the method described above using glass sheets each 3 mm thick, with an intermediate intumescent layer of hydrated sodium silicate, 1.5 mm thick, with a total water content of between 23, 5 and 24.5%. The layer in each such panel was formed of grains with a total water content of 24.5%, which had been sieved so that their dimension was between 150 and 500 μm. The weight ratio of SiO2 to Na2O in the sodium silicate was between 3.3 and 3.4 to 1. The intumescent grains did not include any tetramethylammonium hydroxide as a promotional additive for fire resistance. 10 15 20 25 30 35 505 978 16 A series of comparative sample panels of similar size were also made by a conventional method in which to form each such panel, hydrated sodium silicate solution was dried in situ on a glass sheet 3 mm thick to form layers with an average thickness of 1.8 mm (range 1.5-2.1 mm) with a total water content of between 29 and 34%.

The solution contained 0.25% by weight of tetramethylammonium hydroxide as an anti-aging additive. The weight ratio of SiO 2 to Na 2 O in the sodium silicate was again between 3.3 and 3.4 to 1. A second sheet of 3 mm thick glass was bonded to that layer to form a laminated panel.

The panels were framed in substantially identical frames to form vitrified assemblies for testing by the procedure set forth in International Standard No.. ISO 834-1975. Two glazed assemblies, one from each panel series, were then mounted side by side in the wall of an oven, and the oven was heated according to the required predetermined pattern to test the stability and integrity of the two assemblies as barriers to the passage of flames and smoke according to class REI .

It was found that the comparative test assembly met ISO 834, the RI level for 30 minutes but not for 45 minutes. The assembly comprising a panel according to the invention met the ISO 834, RI level for more than 60 minutes.

Two panel types were subjected to aging tests. In a first test, panels were kept at 80 ° C for 15 days. At the end of that period, no microbubbles appeared in a panel according to the invention, while a considerable number of bubbles appeared in a comparative sample panel, so that it showed haze despite the presence of the silicate stabilizing agent in its intumescent layer. Haze was only prominent in the panel according to the invention after 30 days. In a second test, panels were subjected to UV radiation for 500 hours. The panel according to the invention did not show any microbubbles after that time, but the comparative test panel showed more than twice as many microbubbles as it did after the first aging test. 10 15 20 25 30 35 CO5 97 ”17 EXAMPLE 2 Two additional panel series according to the invention were manufactured using the same starting material as given in Example 1. In these series, the panels consisted of three glass sheets each 3 mm thick and two intumescent intermediate layers each and a 1.5 mm thick. In such a series of panels according to the invention, the intumescent layers comprised a proportion of tetramethylammonium hydroxide; in the second of such a series no such additive was present. The tetramethylammonium hydroxide was included by adding it to the silicate solution of which the grains were formed in a proportion of 0.125% by weight. A series of comparative test panels of the same construction were made from the solution of hydrated sodium silicate with added tetramethylammonium hydroxide as specified for the comparative test panels of Example 1. The intumescent layers of such comparative test panels again had an average thickness of 1.8 mm.

The panels were again framed in substantially identical frames to form vitrified assemblies for testing by the procedure set forth in International Standard No.. ISO 834-1975.

Such glazing assemblies were then mounted side by side in the wall of an oven and the oven was heated according to the required predetermined program to test the stability, integrity and insulation offered by the two series of assemblies according to class REI. It was found that the various assemblies were all able to maintain their integrity as a barrier against the passage of flames and smoke and to meet the insulation requirements according to class REI for between 30 and 35 minutes.

Other members of each series of glazing assemblies were subjected to the aging tests mentioned in Example 1. It was found that according to each test all panels according to the invention gave better results than the comparative test panels and also that of the panels according to the invention those had intumescent material containing tetramethylammonium hydroxide gave better results than those who did not have this. EXAMPLE 3 Two further series of panels according to the invention were manufactured as indicated in Example 2 with the exception of one outer glass sheet in each panel being 2 mm thick instead of 3 mm.

The panels in each series were laminated together with their 2 mm glass sheets to the inside using an intermediate film of polyvinyl butyral (PVB) 0.76 mm thick. Thus, in a series of such PVB laminated panels, each of the four 1.5 mm layers included hydrated sodium silicate with tetramethylammonium hydroxide, while in the second series no tetramethylammonium hydroxide was present.

The panels were again framed in substantially identical frames to form vitrified assemblies to be tested according to the procedure set forth in International Standard no. ISO 834-1975.

The assembly was then mounted side by side in an oven wall and the oven was heated according to the required predetermined program to test the efficiency of the two panel series, again according to class REI. It was found that the assemblies whose panels did not include tetramethylammonium hydroxide were able to maintain their integrity as a barrier to the passage of flames and smoke and to meet the insulation requirements of class REI for periods of 55-70 minutes. The assemblies of the invention, whose panels included tetramethylammonium hydroxide, remained effective as barriers against flames and smoke and met the REI class insulation requirements for periods of 70-80 minutes.

EXAMPLE 4 A further series of vitrified assemblies were made by laminating and then framing three panels each according to the present invention and formed as set forth in Example 2, using intermediate layers of 0.6 mm thick polyvinyl butyral. The assemblies were then mounted side by side in an oven wall and the oven was heated according to the required predetermined program to test their efficiency again according to class REI. It was found that these assemblies according to the invention remained effective as a barrier against flames and smoke and met the insulation requirements of class REI for more than 90 minutes and when tetramethylammonium hydroxide was present as a fire retardant additive they met the requirements of class REI for up to 110 minutes.

EXAMPLE 5 Two refractory panels according to the invention were each manufactured with three glass sheets 3 mm thick and two intumescent layers each 0.6 mm thick. In one panel, the intumescent material included tetramethylammonium hydroxide as a promoting additive for fire resistance specified in Example 2: in the other panel, no such additive was used.

Framed assemblies including the two panels were then tested for their stability, integrity and insulation (class REI) on exposure to fire. The panel without the additive failed after 34 minutes. The panel with the additive withstood the effects of the sample after between 35 and 36 minutes.

EXAMPLE 6 Two fire-resistant panels were each manufactured to contain three glass sheets resp. 3 mm, 8 mm and 3 mm thick and two intumescent layers. In one panel, each intumescent layer was formed in accordance with the invention as set forth in Example 1, to a thickness of 2.5 mm: in the other panel, the intumescent layers were formed to thicknesses of about 1.8 mm by the classical technique as indicated in relation to the comparative test panel mentioned in Example 1.

Framed assemblies including the two panels were then tested for their stability, integrity and insulation (REI class) upon exposure to fire. The comparative test panel failed at 40 minutes. The panel according to the invention withstood the effects of the test for 50 minutes.

Claims (10)

10 15 20 25 30 35 20 Patent claims Transparent, fire-resistant glazing panel comprising at least one layer of intumescent material, bonded to at least one construction layer in the panel, characterized in that the panel comprises such a construction layer, which is bonded to the intumescent layer, such layer being formed by compressing grains of an intumescent hydrated metal salt and which layer has a total water content in the range 20-26%. Panel according to claim 1, characterized in that the panel comprises two construction layers, which are laminated together via a said intumescent layer. Panel according to claim 1 or 2, in that the layer has a total water content of not less than 22%. k ä n n e t e c k n a d Panel according to claim 3, characterized in that the layer has a total water content of not less than 23%. Panel according to one of the preceding claims, characterized in that the layer has a total water content of not more than 25%. Panel according to one of the preceding claims, characterized in that 700 μm and that they are preferably dimensioned between the grains having a maximum dimension of less than 150 and 500 μm. Panel according to any one of the preceding claims, characterized in that the layer or such layer of intumescent material has a thickness of between 0.1 and 5.0 mm. Panel according to any one of the preceding claims, characterized in that the intumescent material comprises hydrated sodium silicate. 505 978 21 Panel according to any one of the preceding claims, characterized in that such a layer of intumescent material contains at least one silicate stabilizing agent. 10. A panel according to claim 9, characterized in that the silicate stabilizing agent comprises at least one nitrogen-containing organic compound, for example an amino compound which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide. 1-0