LU88152A1 - TRANSPARENT FIRE-RESISTANT GLAZING - Google Patents

Description

CLAIM OF PRIORITY G; rand.0 "" BiretcLcjTie

From July 24, 1991

No. 91 16 057.2 Brief Description filed in support of a request for

PATENT OF INVENTION at

Luxembourg

in the name of: GLAVERBEL

Chaussée de la Hulpe, 166 B-1170 Brussels / BELGIUM for: Fire resistant transparent glazing

Fire resistant transparent glass

The present invention relates to a transparent fire-resistant glazing comprising at least one layer of intumescent material secured to at least one structural sheet of the glazing. The invention includes a method of manufacturing such glazing.

Layers of intumescent material are often combined with sheets of glassy material to form fire-resistant glazing. For example, such a layer can be sandwiched between two sheets of glass. Such glazing finds very important uses as transparent panels which allow the lighting of areas to be protected and as windows of premises and other spaces where there is a risk of fire.

Conventionally, the effectiveness of such panels is tested by mounting them in a wall of an oven, the internal temperature of which is then increased according to a predetermined program. Details of such a test are described in International Standard No. ISO 834-1975. The fire resistance test procedure laid down in this standard is also mentioned in International Standard No. ISO 9051-1990 which specifically talks about the fire resistance characteristics of glazed assemblies. Some passages from this standard should be cited here. "Glass is an incombustible material, so it will neither contribute to stoking or propagating fire." Under the action of heat, the glass can break by thermal shock or soften and no longer be held by the frame. This is the reason why only certain types of glazing assemblies are considered to be fire resistant. The ability of glazed assemblies to resist fire depends on the type of glass, the method of implementation, the type of frame, the size of the glass, the method of fixing and the type of construction in which the part glass is installed. "Certain transparent and translucent glazing units may meet the requirements for stability and sealing (RE) and in some cases the requirements for thermal insulation (REI) (R for resistance, E for sealing, I for insulation)." fire prevention, we should not only consider the possibility of direct spread of the fire through the openings resulting from glass breakage, but we must also take into account the heat transmitted by the glass assembly, even if the latter remains intact. since this heat can cause ignition of combustible materials. "RE class glazing units under fire conditions as defined in ISO S34 ensure stability and tightness for a certain period of time. The temperature of the side not exposed to fire is not taken into account. consideration. "Glazed assemblies of the resistance class REI under fire conditions as defined in ISO 834 ensure, for a certain time, stability, watertightness and thermal insulation."

There are different classes of fire-resistant glazing, and among those usually recognized are the classes which include glazing which constitutes an effective barrier against flames and smoke (i.e. class RE) during periods of 15, 30, 45, 60, 90 and 120 minutes. Other classes correspond to glazings which are effective barriers against the passage of flames and fumes and which also exhibit certain insulating properties (i.e. REI class), also during periods of 15, 30, 45 , 60, 90 and 120 minutes, for example.

The insulating properties that a glazing must offer to receive the REI classification of the standard are, in short, that no point on the surface which is exposed outside the oven can undergo a rise in temperature above 180 ° C. above its initial (ambient) temperature, and that the average increase in the temperature of this face does not exceed 140 ° C. Such glazing belonging to the REI class can also constitute barriers against the transmission of infrared radiation coming from the seat of a fire.

It is extremely important that the intumescent layer of fire-resistant glazing has good fire-resistance properties during a fire, and retains acceptable optical properties until it begins to expand upon during the fire.

Hydrated metal salts, for example metal silicates, and in particular alkali metal silicates, have been used in the manufacture of such glazings for several years. The layers incorporated in the finished glazing units typically have a water content of between 29% and 35%. In the present description, references to water contents are references to the water content as a proportion by weight of the intumescent material used to form the layer, or as a proportion by weight of the intumescent material incorporated as as a layer in the finished glazing (before the start of a fire and the modification of this resulting layer). During a fire, the water of hydration is extracted by the heat given off by the fire, and the layer of intumescent material is converted into an opaque foam which acts as a barrier to both irradiated and conducted heat, and this layer is also used to secure the structural sheets of the glazing, such as for example the glass sheets which can break by thermal shock due to fire. The effectiveness of glazing as a barrier against flames and smoke is therefore also prolonged. The effectiveness of glazing of the type known as a fire screen depends on various factors. The effectiveness of a laminated panel consisting of a single layer of a given intumescent material sandwiched between two glass sheets of given thickness increases with the thickness of the intumescent layer. For a previously known panel having a given weight per unit area, that is to say for the same total thickness of glass and intumescent material, the efficiency can be increased by choosing a laminated panel with five sheets, in which there are two layers of intumescent material held between three sheets of glass. In fact, it has often been observed that a laminated panel of three sheets of glass of 4mm each enclosing two layers of 1mm intumescent material is more effective than a laminated panel of two sheets of 6mm glass enclosing a layer of intumescent material of 2mm. The same efficiency can therefore be obtained by using a thinner panel comprising more sheets. It is clear that it is desirable to obtain fire-resistant glazing which has a low mass per unit area, but the formation of glazing with four or more sheets is costly.

Another problem which is associated with the use of hydrated metal salt layers as an intumescent material is the aging of the material over time. Aging results in a deterioration of the optical properties of the glazing, for example a reduction in the transparency of the hydrated intumescent material which, in turn, reduces the transparency of the glazing. Such deterioration of the properties of the glazing is clearly detrimental.

The problem of deterioration of the optical properties by aging of a fire-resistant glazing comprising a layer of intumescent material has been known for many years, and various attempts have been made to solve this problem. A main cause of the deterioration of the optical properties is the appearance of microbubbles in or on the surface of the layer, and it is known to manufacture the layer by in situ drying of a hydrated metal salt solution using water which has been degassed, and taking care, when preparing the solution, not to agitate the solution to such an extent that air or another gas redissolves and may reappear when the dried layer ages. Although this way of proceeding improves the aging properties of the glazing, it is not entirely satisfactory when such glazing must be used in conditions where it is exposed to moderate heat, due for example to direct sunlight. It is also known to add to the hydrated metal salt a stabilizing agent such as a partially dissociated organic nitrogen compound, for example a quaternary ammonium compound such as tetramethylammonium hydroxide, and this method effectively provides better results. .

One of the objects of the present invention is to provide a transparent fire-resistant glazing exhibiting good aging properties which do not essentially depend on the use of such an additive, and which also offers good properties of fire resistance during of a fire.

The present invention relates to a transparent fire-resistant glazing comprising at least one layer of intumescent material secured to at least one structure sheet of the glazing, characterized in that it comprises such a layer of intumescent material secured to a structure sheet, formed by compacting grains of an intumescent hydrated metal salt, and having a total water content of between 20 and 26%.

It has been observed that the optical properties of such glazing are less likely to deteriorate over time than those of a known glazing in which the water content is somewhat higher. In fact, the aging properties of a glazing according to the invention are, all other things being equal, better than those of a glazing whose intumescent material has a higher water content of between 29% and 34% and which incorporates a stabilizing agent such as tetramethylammonium hydroxide. This is quite surprising, and it is not at all clear to us why this advantageous result occurs by using a layer of intumescent material having a lower water content.

It is also surprising that such glazing could have improved fire resistance properties, because one would expect that the lower water content in the intumescent layer would actually reduce the efficiency of the glazing because 'less foam would occur during a fire. In fact, it has been found that a laminated panel with three layers according to the invention comprising a single layer of intumescent material sandwiched between two sheets of glass has better fire resistance than a laminate with three layers of similar dimensions, the intumescent layer has a higher water content. The invention therefore has the additional advantage of allowing the same fire resistance to be obtained by means of thinner and lighter glazing without encountering the additional complications and the cost associated with the increase in the number of laminated glazing sheets.

In addition, the relatively low water content of the intumescent material layer, a maximum of 26%, promotes its hardness, so that it is physically more stable and has less tendency to deform. Producing a layer whose water content is not less than 20% is advantageous for obtaining glazing having good transparency.

Preferably, that said layer has a total water content which is not less than 22%. The presence of such proportions of water in the intumescent layer offers very good foaming properties during a fire, and it also allows the formation of a layer of hard and compact intumescent material which retains good optical properties during time. Optimally, said layer has a total water content which is not less than 23%.

Also to obtain the best results, it is preferred that said layer has a total water content which is not more than 25%, since this promotes the preservation of good optical properties despite the aging of the glazing.

Such a layer of grains can easily be compacted by subjecting it to suitable conditions of temperature and pressure to form a layer in which the individual grains are not visible to the naked eye, so that the layer has a uniform appearance, and is transparent. However, the presence of such grains can be revealed, for example by ultrasonic scanning or by microscopic examination, and it is therefore believed that the boundaries between the grains, although invisible, are maintained within the layer. It is believed that this layer structure can have some effect on the behavior of the intumescent material during a fire, and perhaps even on the properties of the layer before such a fire. A possible contributing factor to the gain in fire resistance of a glazing unit according to the invention could be the following: although the grain boundaries disappear with the naked eye, they can remain and act as a multiplicity of bubble formation sites at the during the reaction of the intumescent material during a fire, which causes a fine frothy structure which has a good uniform insulating effect on the surface of the glazing.

Advantageously, the grains have a maximum dimension less than 700pm, and preferably have a dimension greater than 10pm, for example a dimension between 150pm and δΟΟμτη. This promotes the ease with which the grains can be co-compacted as a layer, and can also have an advantageous effect on the behavior of the intumescent material during a fire. It has been noted that glazings incorporating this preferred characteristic of the invention have a fine and uniform foaming structure when they are subjected to intense heat such as that given off by a fire. It is believed that this is due at least mainly to the low water content of the intumescent material compared to that which has been used to date in the manufacture of fire-resistant glazing, and to the fact that there is a residual granular structure in the compacted layer, but the fineness of the residual granular structure in the layer can also be a contributing factor. The effectiveness of fire-resistant glazing during a fire depends at least partially on the thickness of the (or each) layer of intumescent material. Preferably, the 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 adequate short-term fire protection, although naturally thicker layers provide better protection. In general, increasing the thickness of such a layer beyond 5.0 mm does not confer a significant increase in the degree of protection offered, and it has also been noted that it is more difficult to form layers. thicker compacts with good optical properties.

The intumescent material may be one of many hydrated metal salts, although it is preferred to use an alkali metal salt. Examples of alkali metal salts which can be used in hydrated form are the following: potassium aluminate, potassium leadate, potassium stannate, sodium stannate, double aluminum and sodium sulfate, double aluminum sulfate and potassium, sodium borate, potassium borate, sodium orthophosphates, and potassium silicate. For reasons of cost and efficiency, however, said intumescent material preferably comprises hydrated sodium silicate, which may alternatively be mixed with hydrated potassium silicate.

Preferably, said glazing comprises two structural sheets which are laminated to one another via a said layer of intumescent material. This constitutes a very stable and simple structure. In its simplest form, such laminated glazing could consist of two sheets of glass which are secured directly to the two faces of a layer of intumescent material. Alternatively, when a higher degree of fire protection is desired, two layers of intumescent material could be joined together to form a laminated glazing with three sheets of glass structure. We will easily realize that if we want a higher level of fire protection, we could leaf through one or the other two or more of these glazings, for example by means of a layer of adhesive such as polyvinyl butyral by a process known per se in the technique of manufacturing laminated glazing.

It has already been pointed out that the aging properties of a glazing unit according to the invention are, all other things equal, better than those of a glazing unit whose layer of intumescent material has a higher water content of between 29% and 34 % and which incorporates a stabilizing agent. One would therefore think that there would be no point in using such a stabilizing agent in a glazing whose layer of intumescent material has, according to the invention a low water content, since such glazing has already good aging properties. The use of such a stabilizing agent can however still improve the aging properties of a glazing unit according to the invention, and in addition, it can have a different and completely unexpected advantage: the use of such an agent can improve the fire resistance properties of the layer during a fire, and this is particularly advantageous in a glazing unit having several layers of intumescent material comprising such an additive. Therefore, it is preferred that a layer of intumescent material contains at least one silicate stabilizing agent.

Preferably, the silicate stabilizing agent comprises at least one organic nitrogen compound, for example an amino compound, which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide. It is believed that the incorporation of a stabilizing agent such as tetramethylammonium hydroxide according to this preferred feature of the invention not only provides an additional advantage with respect to the aging properties of the glazing, but also has an effect advantageous on the foam produced during a fire and thus contributes to the efficiency of the glazing as regards its fire resistance.

A glazing unit according to the invention can be manufactured in a very simple manner and the invention includes a method for manufacturing a transparent fire-resistant glazing unit comprising at least one layer of intumescent material secured to at least one sheet of glazing structure, characterized in that grains of an intumescent hydrated metal salt having a total water content of between 22% and 26% by weight are distributed in the form of a layer on a surface of a sheet to be incorporated into the glazing, and in that, while the layer is sandwiched between a pair of molding plates, the layer is subjected to temperature and pressure conditions to degas and compact it, and to cause it to join to this surface of the glazing sheet .

Such a method is implemented very simply and it can be carried out by means of a device already known per se in the technique of manufacturing laminated glazing.

Besides giving good aging and fire resistance properties, the choice of grains of intumescent material having the humidity indicated above has other advantages. The use of grains of intumescent material having a water content which does not exceed 26% promotes excellent conservation of the optical properties of the glazing despite its aging, and such grains are also easy to handle before and during the manufacture of the glazing. Grains of intumescent material having a water content of not less than 22% are very easy to compact into hard and transparent layers, or at least into layers which are transparent when joined between a pair of transparent sheets. This does not mean that the resulting intumescent layer will necessarily have a water content of 22% or more. Some moisture will likely be removed during degassing, but the average water content of the layer will be only slightly less than the average water content of the grains from which it is formed. It has been 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 from grains having an average water content of 25 % will have an average water content between 23% and 25%. When using grains with a lower water content to form the layer, it is highly desirable to control the degassing conditions so as to extract only little water: it is not desirable to have an average content of water in the layer which is less than 20% and preferably such a water content is not less than 22%.

During degassing and compaction, the layer of intumescent material becomes integral with the sheet of glazing with which it is in contact. This sheet may consist of a film of thermoplastic adhesive material for subsequent attachment to a sheet of glazing structure, such as a sheet of glass, but, unless this is desirable for a special reason, this adds a step. additional in the manufacturing process, and it is therefore preferred that said layer of grains is distributed over a surface of a glass sheet which will be incorporated into the glazing and which also constitutes a molding plate.

If it is desired that the other molding plate is not secured to the resulting layer of intumescent material, it can be treated in an appropriate manner, for example with a silicone, but it is preferred that the other molding plate be constituted by, or faces, a sheet which will be incorporated into the glazing and to which the layer of intumescent material will be secured. The layer of intumescent material can therefore be sandwiched between two sheets of the glazing and thus form a laminated panel at the time of degassing and compaction of the layer. In fact, all of the glazing can be assembled into a laminated panel by this degassing and compacting treatment. The glazing can then be transferred to an autoclave for subsequent fastening at high pressure, if desired.

It will be noted that any desired number of successive sheets of glass and of intumescent material can be laminated in this way, but that the difficulty of manufacturing a laminated glazing having good optical properties increases with the number of layers of intumescent material, especially if three or more of these layers must be compacted simultaneously and if the sandwich is to be subjected to heat during the compaction and / or the joining of such layers, as indicated below.

It will be noted that two or more of these glazings consisting of alternating layers of vitreous material and of intumescent material can themselves be joined to one another by means of a film of thermoplastic adhesive material if greater fire resistance is required. Such a method has practical advantages when it is necessary to incorporate several layers of intumescent material.

One could for example wish to produce a fire-resistant glazing having four layers of intumescent material of approximately 1.5 mm each. It has been noted that the thickness of the layers of grains of intumescent material necessary to form such compacted layers can be up to about seven times the thickness of the compacted layers, so that, practically, such glazing can contract by 36mm. during degassing and joining. Manufacturing is simpler from two glazing units each having two layers of intumescent material and by laminating these two glazing units to one another using thermoplastic adhesive film material, such as polyvinyl butyral. The presence of such a thermoplastic adhesive material in film also has an advantageous effect on the fire resistance properties of the glazing by limiting the propagation of cracks due to thermal shock.

In the preferred embodiments of the invention, the grains have a total water content which is not less than 23% by weight, and preferably the total water content is not more than 25%. The presence of such proportions of water in the grains of intumescent material provides the resulting layer with good foaming properties during a fire, and also allows the formation of a hard and compact intumescent layer which retains good optical properties at over time.

Preferably, at least 90% by weight of the grains have a maximum dimension of less than 700 μm, and preferably between 150 μm and 500 μm. Grains of such dimensions are easy to handle and ilos give the resulting compacted layer a structure which is considered advantageous because it offers good fire resistance properties. Such grain sizes are particularly suitable for forming the layers of the particularly targeted thicknesses, for example layers having a thickness between 0.1mm and 5.0mm.

Advantageously, the layer of intumescent material is subjected to a temperature of at least 80 ° C., for at least part of the degassing and joining time. Heating the intumescent material to such a temperature promotes degassing and compaction, and also securing it to a sheet of glazing. It will be noted that the intumescent material cannot be subjected to temperatures such that, under the conditions of pressure exerted on the material, they 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, of a glazing is subjected to an optimal temperature program than to ensure this for each of the layers. of an assembly comprising three or more layers, because the central layer (s) is / will be more protected from the heat source by the other sheets of the glazing than the external layers will be.

Advantageously, during the degassing and the joining, the layer of intumescent material is subjected to a pressure of less than 30 kPa. This allows excellent degassing of the intumescent layer.

The use of additives in an intumescent layer has been mentioned above to improve the aging properties. The use of such an additive can have other unexpected advantages by promoting fire resistance during a fire, as mentioned above. Advantageously, therefore, the layer of intumescent material contains at least one silicate stabilizing agent and, preferably, the silicate stabilizing agent comprises at least one nitrogenous 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:

Figure 1 is a schematic view of a device for degassing and compacting a layer of intumescent material in a method according to the invention.

In FIG. 1, a sandwich consisting of two glass sheets 1, 2 and an intermediate layer 3 made up of grains of intumescent material having a total water content of between 22% and 26% has been formed. The grains have a dimensional fraction which passes through a sieve whose meshes have 500 μm, but which is retained by a sieve whose meshes have 150 μm. The grains are simply spread freely on a first sheet of glass and leveled to obtain a layer of grains seven times the desired final thickness of the compacted layer. The sandwich is enclosed in an envelope 4. The envelope is connected via a vacuum line 5 to a pump 6 by which one can maintain a sub-atmospheric pressure inside the envelope and maintain under suction the space between the sheets 1, 2. When the pump is operating, the lower and upper walls of the envelope are attracted against the main external faces of the sandwich which is enclosed therein, and the glass sheets 1, 2 act as molding plates for compact the granular intumescent layer 3. The envelope is rigid enough at least at its peripheral zone 7, to resist its collapse against the slices of the sandwich, so that a space 8 at a pressure below atmospheric pressure (maintained by the pump 6) is arranged inside the envelope, around the edges of the sandwich 1, 2, 3. The use of an envelope which encloses the sandwich has the advantage that the dimension of the envelope by ra The size of the sandwich is not critical. The envelope can easily be used to hold sandwiches of different dimensions. In addition, the use of such an envelope facilitates the application of uniform pressure over the entire surface of the main faces of the sandwich during its treatment, so that the reaction forces resulting from pressure differences between the atmosphere in which the envelope is placed and the space inside the envelope will not be sufficient to cause the bending of the outer sheets 1, 2 of the sandwich. Such bending could lead to the formation of bubbles in the margins of layer 3 and could also lead to the formation of a non-planar final product.

As a variant of the device which has just been described, optional reinforcing means are arranged to support the reaction forces originating from the pressure differences between the interior and the exterior of the envelope 4. In FIG. 1, such reinforcing means are shown in the form of a pair of frames 9 of the same shape but slightly larger than the sandwich 1, 2, 3, which are kept spaced apart by several spacers such as 10. The frames 9 are spaced apart by the spacers 10 so as to keep the envelope slightly spaced from the edges of the assembly when the intumescent layer has its thickness reduced to the final compacted dimension shown in the drawing.

Heating devices (not shown) can be arranged on the upper and lower faces of the casing 4 to heat the intumescent material 3 sandwiched and to aid in the compaction and the joining of the sandwich.

A sandwich can be treated by the suction means represented in FIG. 1 in a very simple process in which the outside of the envelope 4 is always subjected to atmospheric pressure. In an example of the method, the pump 6 is put into action. To reduce the pressure inside the envelope, that is to say the pressure acting on the edges of the sandwich in the peripheral space 8, to a value less than 30kPa. The precise optimum value will depend on the water content of the intumescent grains used. The desired value can be reached after only a few minutes, and it can be maintained for a hundred minutes. The sandwich is initially at room temperature (20 ° C). The sandwich in the casing 4 is heated so that it reaches a temperature of 90 ° C after 45 minutes.

After the required degassing, the pressure inside the envelope is allowed to return to atmospheric pressure over a period of about 15 minutes. At the end of this period, the granular layer has been compacted to such an extent that the boundaries between the grains have become invisible to the naked eye and the sandwich is secured in the form of a transparent laminated panel. Obviously this panel can be transferred to an autoclave for a subsequent step of high pressure joining, if desired.

The water loss of the intumescent layer due to suction during the compaction of the layer is less than 2% relative to the weight of the layer. EXAMPLE 1

A series of glazings is produced by the process described above using glass sheets 3 mm thick each and an intumescent intermediate layer of hydrated sodium silicate 1.5 mm thick, having a total content of water between 23.5% and 24.5%. The layer of each of the glazings is formed of grains having a total water content of 24.5% which have been sieved so that their size is between 150μτη and 500μηι. The weight ratio Si02 / Na20 in sodium silicate is between 3.3 and 3.4 to 1. The intumescent grains do not include tetramethylammonium hydroxide as an additive promoting fire resistance.

A series of comparative control glazings of the same dimensions are manufactured by a conventional process in which, to form each of the glazings, a solution of hydrated sodium silicate is dried in situ on a sheet of glass 3 mm thick to form layers close to 1 , 8mm thick (between 1.5mm and 2.1mm) with a total water content of between 29% and 34%. the solution comprises 0.25% by weight of tetramethylammonium hydroxide as an additive against aging. The Si02 / Na20 weight ratio in the sodium silicate is between 3.3 and 3.4 to 1. A second sheet of glass 3mm thick is joined to this layer to form a laminated glazing.

The glazings are mounted in substantially identical frames to form glazed assemblies intended to undergo tests according to the procedure of International Standard No. ISO 834-1975.

Two glazed assemblies, the glazings of which come from each of the two series of glazings, are then mounted side by side in an oven wall. The oven is heated according to the predetermined program required in order to test the stability and tightness of the two assemblies as barriers against the passage of flames and fumes according to class RE. The comparative control set is found to meet ISO 834 at the RE class of 30 minutes, but not at the 45 minute class. The assembly comprising the glazing according to the invention complies with ISO 834 in the RE class of more than 60 minutes.

The two types of glazing are then subjected to aging tests. In a first test, the glazings are maintained at 80 ° C for 14 days. At the end of this period, no bubbles appear in the glazing according to the invention, while a considerable number of microbubbles appears in a comparative control glazing, so that it has a haze despite the presence of silicate stabilizer in the intumescent layer. The veil only appeared in the glazing according to the invention after 30 days. In a second test, glazing units are subjected to UV radiation for 500 hours. The glazing according to the invention does not present microbubbles after this period, but the comparative control glazing shows more than twice as many microbubbles as after the first aging test. EXAMPLE 2

Two other series of glazings according to the invention are manufactured using the same starting materials as in Example 1. In these series, the glazings consist of three sheets of glass of 3 mm each, and two intermediate layers of intumescent material of 1 , 5mm thick. In one of these glazing series according to the invention, the intumescent layer comprises a proportion of tetramethylammomium hydroxide; in the other series, there is not this additive. Tetramethylammomium hydroxide is incorporated by adding it to the silicate solution from which the grains are formed, in a proportion of 0.125% by weight. A series of comparative control glazings of the same structure is manufactured from a hydrated sodium silicate solution with the addition of tetramethylammonium hydroxide, as has been described for the comparative control glazings of Example 1. The intumescent layers of these comparative control glazings again have an average thickness of 1.8 mm.

The glazings are again mounted in substantially identical frames to form glazed assemblies intended to undergo tests according to the procedure of International Standard No. ISO 834-1975.

Such glazed assemblies are then mounted side by side in an oven wall. The oven is heated according to the predetermined program required in order to test the stability, the tightness and the insulation offered by the two series of glazings according to class RE.I. It is found that the different assemblies are all capable of maintaining their tightness as a barrier against the passage of flames and fumes and of satisfying the insulation requirements of the REI class for 30 to 35 minutes. Other parts of each series of glazings are subjected to the aging tests cited in Example 1. It is found that, according to each test, all the glazings according to the invention give better results than the comparative control glazings and also that, among the glazings according to the invention, those whose intumescent layer comprises tetramethylammonium hydroxide provide better results than those which do not contain them. EXAMPLE 3

Two sets of glazing units are produced according to the invention as described in Example 2, except that one of the outer glass sheets of each glazing unit is 2mm thick instead of 3mm. The glazings of each series are laminated together, so that their 2mm glass sheets are arranged inside, using 0.76mm thick polyvinyl butyral (PVB) films. So, in a series of these PVB laminated glazings, each comprising four layers of 1.5 mm thick hydrated sodium silicate comprising tetramethylammonium hydroxide, while in the other series, there is no tetramethylammonium hydroxide.

The glazings are again mounted in substantially identical frames to form glazed assemblies intended to undergo tests according to the procedure of International Standard No. ISO 834-1975.

The glass assemblies are then mounted side by side in an oven wall. The oven is heated according to the predetermined program required in order to test the efficiency of the two series of glazings according to the REI class. It is found that the assemblies which do not contain tetramethylammonium hydroxide are capable of maintaining their tightness as a barrier against the passage of flames and fumes and of meeting the insulation requirements of the REI class for 55 to 70 minutes. The assemblies according to the invention which contain tetramethylammonium hydroxide are capable of maintaining their tightness as a barrier against the passage of flames and fumes and of satisfying the insulation requirements of the REI class for 70 to 80 minutes. EXAMPLE 4

Another series of glazings is manufactured by laminating together, by means of intermediate layers of polyvinyl butyral 0.76 mm thick, three glazings themselves according to the invention, manufactured according to example 2. The glazings are then mounted in frame to form glass units. The glass assemblies are then mounted side by side in an oven wall, and the oven is heated according to the predetermined program required in order to test their efficiency according to class RE.I. It is found that these assemblies according to the invention remain effective as a barrier against the passage of flames and fumes and meet the insulation requirements of the REI class for more than 90 minutes. When tetramethylammonium hydroxide is present as a fire resistance additive, they meet the requirements of the REI class for up to 110 minutes. EXAMPLE 5

Two fire-resistant glazing units are produced according to the invention, each containing three sheets of glass 3mm thick and two intumescent layers each 0.6mm thick. In a glazing, the intumescent material contains tetramethylammonium hydroxide as an additive promoting fire resistance, as described in Example 2; in the other glazing, this additive is not used.

Assemblies with frames incorporating the two glazing units are then tested for stability, tightness and insulation (REI class) when exposed to fire. Glazing without additives fails at 34 minutes. Additive glazing withstands the effects of the test for 35 to 36 minutes. EXAMPLE 6

Two fire-resistant glazing units are produced, each containing three sheets of glass 3mm, 8mm and 3mm thick, respectively, and two intumescent layers. In a glazing, each intumescent layer is formed according to the invention, as described in example 1, with a thickness of 2.5 mm; in the other glazing, the intumescent layers are formed with a thickness of approximately 1.8 mm by the conventional technique, as has been described with regard to the comparative control glazing cited in Example 1.

Assemblies with frames incorporating the two glazing units are then tested for stability, tightness and insulation (REI class) when exposed to fire. Comparative witness glazing fails at 40 minutes. The glazing according to the invention resists the effects of the test for 50 minutes.

Claims (22)

1. Transparent fire-resistant glazing comprising at least one layer of intumescent material secured to at least one structure sheet of the glazing, characterized in that it comprises such a layer of intumescent material secured to a structure sheet, by compacting grains of an intumescent hydrated metal salt, and having a total water content of between 20 and 26%. 2. Glazing according to claim 1, characterized in that it comprises two structural sheets which are laminated to one another by means of such a layer of intumescent material. 3. Glazing according to one of claims 1 or 2, characterized in that said layer has a total water content which is not less than 22%. 4. Glazing according to claim 3, characterized in that said layer has a total water content which is not less than 23%. 5. Glazing according to one of claims 1 to 4, characterized in that said layer has a total water content which is not more than 25%. 6. Glazing according to one of claims 1 to 5, characterized in that the grains have a maximum dimension less than 700μτη, and preferably have a dimension between 150pm and 500pm. 7. Glazing according to one of claims 1 to 6, characterized in that the or said layer of intumescent material has a thickness between 0.1 and 5.0 mm. 8. Glazing according to one of claims 1 to 7, characterized in that said intumescent material comprises hydrated sodium silicate. 9. Glazing according to one of claims 1 to 8, characterized in that such a layer of intumescent material contains at least one silicate stabilizing agent. 10. Glazing according to claim 9, characterized in that the silicate stabilizing agent comprises at least one nitrogenous organic compound, for example an amino compound, which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide. 11. A method of manufacturing a transparent fire-resistant glazing comprising at least one layer of intumescent material secured to at least one structure sheet of the glazing, characterized in that grains of an intumescent hydrated metal salt having a total content of water between 22% and 26% by weight is distributed in the form of a layer on a surface of a sheet to be incorporated into the glazing, and in that, while said layer is sandwiched between a pair of plates molding, it is subjected to temperature and pressure conditions to degas and compact it, and to cause it to join to this surface of the sheet of the glazing. 12. Method according to claim 11, characterized in that said layer of grains is distributed over a surface of a glass sheet which will be incorporated in the glazing and which also constitutes such a molding plate. 13. The method of claim 12, characterized in that the other molding plate is constituted by, or faces, a sheet which will be incorporated in the glazing and to which the layer of intumescent material will be secured. 14. Method according to one of claims 11 to 13, characterized in that the grains have a total water content which is not less than 23% by weight. 15. Method according to one of claims 11 to 14, characterized in that the grains have a total water content which is not more than 25%. 16. Method according to one of claims 11 to 15, characterized in that at least 90% by weight of the grains have a maximum dimension less than 700pm, and preferably between 150pm and 500μτη. 17. Method according to one of claims 11 to 16, characterized in that the layer formed has a thickness between 0.1 and 5.0mm. 18. Method according to one of claims 11 to 17, characterized in that the layer comprises hydrated sodium silicate. 19. Method according to one of claims 11 to 18, characterized in that, during at least part of the degassing and joining time, the layer of intumescent material is subjected to a temperature of at least 80 ° C. 20. Method according to one of claims 11 to 19, characterized in that, during degassing and joining, the layer of intumescent material is subjected to a pressure of less than 30kPa. 21. Method according to one of claims 11 to 20, characterized in that the layer of intumescent material contains at least one silicate stabilizing agent. 22. Method according to claim 21, characterized in that the silicate stabilizing agent comprises at least one organic nitrogen compound, for example an amino compound, which is at least partially dissociated, for example a quaternary ammonium compound such as tetramethylammonium hydroxide.