CA1049912A

CA1049912A - Fire screening glazing panel and a method of producing same

Info

Publication number: CA1049912A
Application number: CA196,287A
Authority: CA
Inventors: Francis Jacquemin; Jean-Pierre Voiturier; Robert Terneu
Original assignee: Glaverbel Mecaniver SA
Current assignee: Glaverbel Mecaniver SA
Priority date: 1973-03-30
Filing date: 1974-03-28
Publication date: 1979-03-06
Also published as: AT343843B; DE2414575A1; DE2414575C2; NO134865B; FR2223323B1; FI55705C; BE812752A; SE398342B; NL7404023A; NO134865C; FI55705B; IE39104B1; IE39104L; ES202218U; JPS5018513A; JPS582176B2; CH599410A5; ES202218Y; GB1451931A; IT1011610B

Abstract

ABSTRACT OF THE DISCLOSURE

A fire screening glazing panel and a method of producing same. A panel is formed of at least two structural plies and at least one of which is a vitreous sheet, layers of heat convertible thermally insulating barrier forming material are placed on a face of each ply, and a plastic membrane is sandwiched between the layered plies, the layers being adjacent the plastic membrane. When formed in this way, the plastic membrane makes the transfer of heat from one barrier-forming material layer to the other more uniform and prolongs the time taken for the vitreous sheet to reach a given temperature, while the panel as a whole is in itself sufficient to prevent or delay propagation of fire across an opening closed by the panel. Protective strata may be applied to each vitreous ply on its face that will be in contact with the barrier forming material layer to inhibit interaction between the ply and the layer and preserve the transparency (if the ply is transparent) of the ply over an extended period of time.

Description

~049gl2 This application is related to our copending Canadian application Serial Nos. 196,290 and 196,291, which were filed on the same date as this case.
This invention relates to a fire-screenirlg glazing panel comprising a fire screening means which becomes operative when sufficiently heated.
In the construction of buildings, glazing panels sometimes are used in exterior or interior walls or partitions. An obvious example is the use of light_transmitt-ing glazing panels used as windows.
Structural components occasionally must satisfystringent standards of fire resistance. Fire resistance is sometimes quantified against a standard test in which the structural component is exposed to a specified temperature cycle over a certain period of time. The fire resistance potential of the component depends on the length of time for which the component can retain the strength required for it to fulfill its function. To comply with some fire resist-ance standards the component must have a minimum strength retention time, must be completely flame-proof, and must pro-vide enough thermal insulating power to ensure that the com-ponent will prevent propagation of fire by heat radiation from the component and will not become so hot as to result in serious risk of burning a person who may touch the panel while it is exposed to the fire. ~ -

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The standard of fire resistance of a given component may be quantifled as a function 3f the tlme for which the co~ponent satisfies one or more of the speclfied criteria during a test in which the component i3 exposed to the interior of an enclosure in which the temperature is raised according to a predetermined schedule, For example standards of fire resistance designated 1, 2 and 3 may be set corresponding to resistance times of 15, 30 and 60 minutes respectively in a test in which the temperature of the test enclosure is 720, 820 and 925~C
respectively for each time period.
Ordinary panel~ comprising one or more sheets of vitreous material are not highly thermally insulating or fire resistant. When exposed to fire~ t~ey become very hot so that they cannot be touched without causing personal injury, Moreover heat radiation from the heated panel itself constitutes a further fire hazard.
Various proposals have been made for dealing with this problem, One proposal is to install in a building having door and window openings sprinkler heads for supplying a fire-extinguishing agent, e,g, water, The sprinkler heads are placed above each door and window opening of the build~ng and communicate with a common reservoir containing the fire extinguishing agent, When fire occurs, the sprinkler heads supply fire extinguishi~g agent along the doors and windows, Such installations have certain disadvantages, Among those disadvantages is the ~act that the installations are complicated and can-not be easily installed,

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It is an object of the invention to provide a fire-screening glazing panel which can be easily and conveniently handled and installed. It is a further object to provide such a panel which has improved thermal insulating and fire-resisting properties. In particular the invention seeks to provide a panel which is resistant to mechanical breakage when subjected to rapid heating by a heat source disposed on one side of the panel.
The present invention as broadly defined resides ~0 in a fire-screening glazing panel comprising a fire-screening means which becomes operative when sufficiently heated charac-terized in that the panel comprises a first structural ply formed by a vitreous sheet and at least one other structural ply, and characterized in that between the said first structural ply and the other or another structural ply there is sandwiched at least one plastic membrane and, on opposite sides of said membrane(s), layers, at least one of which is composed of at least in part of material which when sufficiently heated is converted to form a thermally insulating barrier or barriers which is or are opaque or of greatly reduced infra-red radiation transmitting power as compared with such layer before such conversion.
Stated in other words, the invention resides in fire screening panel comprising a first structural ply formed by a vitreaous sheet and at least one other structural ply formed by a vitreous or plastic sheet characterised in that there is present at least one plastic membrane having on opposite sides thereof a layer composed at least in part of a material comprising a hydrated metal salt which when sufficien-tly heated forms a solid porous or cellular body forming athermally insulating barrier said barrier forming layers and b .

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~0499~2 and said plastic membrane being sandwiched between said first and other structural ply.
The expression "Vitreous material" as used herein comprises glass and vitrocrystalline rnaterial.

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V~trocrystalline material is formed by sub~ecting a glass to a thermal treatment sc as to induce the formation of one or more crystalline phases therein.
~lle invention a~fords a number oP advantages which ar~ considered to be important.
~ first advantage is the fact that the ~ire-screening ~lazing panel is very easy to install and is in itself suf~icient to prevent or to delay the propagation of f1re across an opening closed by the panel, A second advantage i8 the fact that if the panel is installed as part of a ~Jall of an enclosure in which fire break~ out so that the plastic membrane is disposed between the first structural ply and the interior of said enclosure, the plastic membrane obviates or reduces tendency for 1OCR1 over-heatin~ of the ~irst ply to take place with consequent risk of breakage thereof, The area which is immediately behind the plastic membrane (the area occupied by that one of the sandwiched layers which is nearer the fire) may become non-uniformly heated due, for example, to the behavior of the material of that layer on being heated and converted to form a thermally insulating barrier. However tlle plastic membrane will serve to ensure a more uni~orm distribution of the heat transmitted to the sandwiched layer which is in front of the membrane and to the first structural ply, 10499~
~ third advantage i6 that u~c3er t~le circumstance~
referred to, the tlme taken f`or the vltreous sheet constituting the first ply to reach a given -temperature is prolonged due to the presence of the membrane. The vi~reous sheet can therefore provide the exterior face of the panel which is exposed to touch, with less risk of causing burns than would be involved in using a panel of known constructlon and comparable weight.
As has been stated, at least one layer of barrier forming substance is convertible by hea~ to form a barrier which is of greatly reduced infra-red radiation transmitting power, or which is opaque This feature allows the formation of very effective f~re screens since the intensity of any infra-red radiation from a fire on ~15 one side of the panel which is transmitted through the panel may be reduced to a level at which it cannot, of itself, start a secondary fire on the other side of the panel.
It w~ll be appreciated that if the panel were installed in reverse orientation to that above described, i e.~ with the said first ply between the fire and the plastic membrane, a corresponding advantage will be achieved~ namely that the plastic membrane will slow down the heating of the other face of the panel In such a case that front face may be formed for example by another vitreous sheet.

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Tl~e lnvention ls equally applicable to opaque panels and light-transmitting panels.
~le use oP opaque glazing panels, i.e~ panels comprising one or more sheets of glass or vitrocryst~lline material, is becoming increasingly important in architecture and such panels are often used to form, ~or example, the lower part of a partition ~1hose upper part is transparent, especially when it is desired that t~e surface texture or some other property of the panels forming the upper and lower parts of the partition be similar. Preferably however, the panel is a light transmitting panel, so that it may be used, for example, as an observation window until the advent of fire.
Advantageously, the barrier forming material i8 convertible by heat to form a solid porous or cellular body, since such bodles generally have 10W thermal conductivity.
Preferably, said barrier forming material comprises an hydrated metal salt.
Examples of metal salts which can be used in hydrated form are as ~ollows:
Aluminates, e g. sodium or potassium aluminate Plumbates, e.g, sodium or potassium plumbate Stannates, e g, sodium or potassium stannate Alums, e g. sodium aluminum sulphate or potassium aluminum sulphate Borates e.g. sodium borate Phosphates, e.g. sodium orthophosphates, potassium orthophosphates and aluminum phosphate ~049912 Hydrated alkali metal silicates, e g sodium . ., _ ... ,~ ,.. .. .
silicate, ~re also suitable for use in a said layer incorporating heat-convertible material Such substsnces ha~e very good properties for the present purposes. They are in many cases capable of ~orming transparent layers which adhere well to glass or vitrocrystalline material. On being ~ufficiently heated, the combined water boils and the layers foam, 80 that the hydrated metal salt i8 converted into an opaque solid porous or cellular form in which it is highly thermally insulating and remains adnerent to the glass or vitrocrystalline material.
This feature is particularly important, since even if all the structural plies of the panel are cracked or broken by thermal shock, the panel may retain its . ef~ectiveness as a barrier against heat and fumes since .
the fragments of the plies may remain in position bonded together by the converted metal salt If a panel according to the invention and incorporating such hydrated metal salt sandwiched layers i8 exposed to fire, the water in the salt layer which is nearer the .~ire is first boiled off As this layer is .~ heated the other hydrated metal salt layer is kept at a somewhat lower temperature due to the presence o~ the plastic membrane. During boiling off of the combined water of the first sandwiched layer, its temperature ., ., .

remains substantially constant, and thermal conversion of the fire screening material on the said other sand-wiched layer is delayed. As the combined water becomes completely removed from the sandwiched layer nearer the fire this la~er be_omes er~ective as a thermal barrier.
In some embodiments, a layer of hydrated metal salt is used which is merely translucent, but preferably the hydrated metal salt forms a transparent solid layer at ambient temperature. Sodium silicate, sodium aluminum sulphate and aluminum phosphate can form transparent layers.
It has been found that vitreous sheets may suffer deterioration to varying degrees by prolonged contact with various barrier-forming materials e.g. hydrated metal salts. This is particularly important in the case of transparent or colored sheets, since they may suffer a loss of transparency or undergo a change in color.
Preferably, therefore, a protective stratum , .
is provided between said first structural ply and the 2~ adjacent heat convertible layer said protective stratum being formed so as to inhibit interaction between the barrier forming rnaterial and the first structural ply.
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If the other structural ply is also a . .
vitreous sheet, a protective stratum is preferably like-~25 wise provided between that other vitreous sheet and the ad~ecent leyer of barrier-forming meterial.

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Thls feature is equally applic~ble in cases where the panel is a true laminate, i,e, a multi-ply panel wllose plies are bonded together face to face, and where it is a multi-ply panel whose plie3 ~re held clamped together by extraneous means, such as a frame.
In so~e preferred embodiments, the protective stratum comprises a sheet of substantially water-impervious plastic material. Polyvinyl butyral is an especially suitable material for forming a plastic protective stratum, which may for example be 0.76 mm thick, though any other film-forming plastlcs material having the requisite properties may be used.
In other preferred embodiments of the invention there is at least one protective stratum which comprises a coating applied to the vitreous sheet face to be protected. Such a coating preferably comprises an anhydrous metal compound deposited onto such sheet face, since such coatings can form very effective protective strata, , 20 Clearly, one criterion affecting choice of a suitable coating material will be the composition of the thermally insulating barrier formin~-layer By way of .
example when the barrier ~ rming material is of sodium silicate~ ~r ~ or an~alumlof potassium or sodium, then ; 25 the coating material preferably comprises zirconium oxide '~

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., or anhydrous a]uminum phosphate~ ~hen the thermally insulatlng barrier formine layer is of hydrated alumlnum phosphate, then titanium oxide, zlrconium oxide~ tin ; oxide and anhydrous alumlnum phosphate are eminently suitable protective coating materials, It is, perhaps, surprising to note that a protective stratum of anhydrous aluminum pllosphate when deposited onto a vitreous sheet will serve substantially to prevent interaction between that vitreous sheet and an adjacent layer of hydrated aluminum phosphatc, This invention does not exclude the use of other coating materials, . .. .. ..
Preferably the protective stratum when constituted by a coating as aforesaid is between 100 and 1,030 Angstro~ units thick, so as to provide a non-porous coating WitilOUt giving rise to unsightly inter-ference effects.
Preferably, at least one said layer of barrier forming n~terial is between 0.1 mm and 8 mm in thiclcness, f~ Layers having this range of thickness can be converted to become very effective fire-screening barriers. It ~ is clear that the effectiveness of a fire-screening ;~ barrier formed from a layer of given material will depend on its thickness, however, the transparency of such a layer will become less with increa~ed thickness, Preferably at least one layer of heat-convertible material has a thiclcness of between 0.1 and 0,5 mm.

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104~912 The plastic membrane or memblanes in a panel accordlng to the invention can be ~ormed of any film-f~rming pl~s~ic ma~erial havin~ tlle requis~te properties.
Preferably the panel incorporates at least one plastic membrane composed of polyvinylbutyral, since this material is especially suitable.
Polyurethane is also a very ~uit~le material for forming st least one of said membranes, and indeed, polyurethane is also suitable for forming a plastic protective str~tum, Preferably the first structural ply and/or at least one other vitreous sheet (if present) of the panel is tempered, A tempered vitreous sheet is better able to withstand thermal shocks, Chemically tempered sheets are particularly preferred, A panel according to the invention preferably comprises two structural plies, each constituted by a vitreous sheet and each providing an external face of the panel, Such a panel structure has a merit of simplifi ty, It is to be understood however that it i9 within tl~e scope of the invention for the panel to incorporate more than two structural plies, The invention also includes panels where a plastic membrane, together with layers of , thermal barrier forming material on opposite sides of ; 25 the membrane, is present in each of the two or more inter- ply spaces, 1(~4991Z
According to preferred embodiments of the invention the panel is in the form of a laminate, i.e., a multi-ply panel structure in which the first vitreous sheet, at least on~ other structural ply, a plastic membrane between the plies and the heat convertible layers on opposite sides of the membrane are bonded together in face to face relation.
The invention however also includes multi-ply panels in which the first ply, another structural ply, a plastic membrane intervening between the plies, and heat convertible layers on opposite sides of the membrane are held together by extraneous means, e.g., by means of a frameO
The invention also includes an article which comprises a multi-ply panel according to the invention as hereinbefore defined together with a second panel (comprising a single sheet or a plurality of sheets) held in spaced relationship to said multi ply panelO Thus the invention can be embodied in a hollow glazing unit.
As already stated, embodiments of the invention in which the panel is in the form of a laminate are preferred.
The invention also includes a method of forming a laminated fire-screening glazing panel comprising a first structural ply formed by a vitreous sheet and at least one other structural ply formed by a vitreous or plastic sheet comprising the steps of a) applying onto one face of said first ply a layer composed at least in part of material comprising a hydrated metal salt which when sufficiently heated forms a solid porous or cellular body forming a thermally insulating barrier, b) applying another said layer to another structural ply, ~ c) assembling said layered plies on opposite sides ,~ of a plastic membrane with said applied layers adjacent thereto, and ~04~91~
d) subjecting said assembly to heat and pressure to bond said coated plies and said plastic membrane together to form a laminate. This is a very simple and effective way of forming a laminate-typ~ panel according to the teachings of the present invention. The method obviates any need to apply adhesive between the coatings on the structural plies and the plastic membrane.
j Preferably, at least one of the heat convertible 10 ¦ layers is formed of an hydrated metal salt/ said hydrated metal salt preferably being selected from the following groups aluminates, plumbates, stannates, alums, borates, phosphates ; and alkali metal silicates. The advantages conferred by these . ~. ..................................................... .
method steps correspond to the advantageous features of the , ¦ panel formed according to the teachings of the present invention.
, ~ Advantageously, the hydrated metal salt layers are applied as aqueous solutions which are dried before assembly of the panel. For example, in order to obtain a layer of hydrated aluminum phosphate, an aqueous solution ~ 20 containing 3.5 moles/litre of the salt is applied to a sheet, ; and subsequently dried by using a :

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fan This solution may be o~tained hy mix~ng solution~
of phosphoric acid and aluminum chloride in stoichiometric proportions. This is a very simple way of obtaining the required layers of barrier forming m~terial.
Pre*erably a protective stratum i9 formed on a face of the vitreous first structural ply before a heat convertib]e layer is applied thereto, the pro-tective stratum being composed of a material selected so as to inhibit interaction between the barrier forming material and the first structural ply. Preferably a protective stratum is formed on each vitreous sheet face of the panel onto which a layer of barrier forming material is subsequently applied. Preferably at least one such protective stratum is formed as a sheet of ; 15 substantially water impervious plastlc material, and advantageously the plastic protective stratum i8 formed of polyvin~l butyral. In preferred embodiments of the method according to the teachings of the present invention ; at least one protective stratum is applied to a vitreous sheet face as a coating. Preferably, such a protective stratum is formed by depositing a coating of an anhydrous metal compound onto a vltreous sheet face The advantages of these preferred method steps according to the teachings of the present invention are apparent from the correspond-ing advantages of the panel formed according to the teachings of the present invention.

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Such a deposltion of an anhydrous metal compound coating to serve as a protective stratum is preferably performed by pyrolysis or hydrolysls, since these are very convenient ways of forming a uniform coating which is higilly resistant to the deleterious effects of a barrier forming material.
Preferably, the barrier forming material is selected ~rom the group consisting of alums, borateR, and alkali metal silicates, and the anhydrous metal compound ; lO for forming a protective stratum is selected from the group consistlng of zirconium oxide and anhydrouR
aluminum phosphate, however, the barrler ~orming material may comprise hydrated aluminum phosphate, the anhydrous metal compound for forming a protective stratum then being selected ~rom the group consisting of titanium oxide, zirconium oxide, tin oxide and anhydrous aluminum phosphate, Advantageously, a protective coating is ~ormed to a thickness of between lO0 and lO00 Angstrom units.
Preferably, at least one heat-convertible layer is formed to a thickness of between 0.1 mm and 8 mm, and optimally, such a heat convertible layer is formed , to a thickness of between 0.1 mm and 0.5 mm. In pre~erred embodiments of the method according to the teachings of the present invention, said coated plies are assem~led ~ and bonded to~ether on opposite sides of a said membrane 1 of plastic material comprising polyvinyl butyral .~

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1049~12 In such a method according to the teachingR
of the present invention it i~ preferable for the layerq applied to the structural plies to be layers of one or more hydrated alkali metal silicates, since such barrier forming materials are more readily able to withstand the bonding temperature required tllan certain other hydrated metal salts herein set forth.
; In some preferred embodiments of the method according to the teachings of the present invention the coated structural plies are assembled on opposite sides of a layer of plastic membrane forming material comprising an organic monomer with the applied heat convertible layers next to said monomer containing stratumj and the assembly is sub~ected to heat and pressure to polymerize the monomer in situ and bond the coated structural plies together on either side o~ the plastic membrane thus formed. Embodiments having this feature have the advantage that the polymeriz~tion temperature may be kept below 80C by suitable choice of organic monomer, and this ~0 obviates risk of premature conversion o~ the barrier form-ing layer during the bonding process.
Urethane i8 a very suitable organic monomer for incorporating in ~uch layer.
; When a plastic membrane is formed in this manner it is very convenient to form the plastic pro-tective stratum in a like manner.
The invention will now be described by way of example with reference to the accompanying diagrammatic ~17-.. . ~ . _ .
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drawings in wl-ich figure~ 1 to 5 are cross~sec~ional v~ews of various preferred embodiments of fire screening glazing panels ~ccording to the teachings of the present invention ~ fire screening panel was made as shown in ? figure 1. This panel comprises two sheets 1,1 of glass e~ch of which~carries a layer 2 of hydrated sodium silicate, ~nd these layers are bonded together on opposite ~; 10 sides of a membrane 3 of polyvinyl butyral.
The glass sheets 1 are of soda-lime glass 3mm thick, the layers 2 of hydrated sodium silicate are each 2.5mm thick, and the plastic membrane 3 has a thick-' ness of 0.76mm.
'~ 15 In order to form the layers 2, hydrated sodium ~ilicate was applied in an aqueous solution having the follo~ing properties:
Proportion by weight Si2 .
Viscosity 200 centipoises Specific gravity 37 to 40 Baumé

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This solution was applied to a face of each glass sheet while the sheets were substantiQlly horizontal and at a temperature of 20C. ~le solution thus applied was allowed to spread out over the glass sheets.

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Current~ of warm air were then directed onto the solution in order to dry it. Thls drying has the effect of driving off excess, unbound water of solution to leave a layer of hydrated sodium silicate on each glass sheet. After ~ormation of these layers of hydrated sodium sillcate on the sheets, the sheets were p~ ced on either side of a sheet 3 of polyvinyl butyral 0.76 mm thick as shown in figure 1, In order to bond the panel together to form a laminate, the assembled panel was placed in a chamber in which reduced pressures could be obtained. Reduction in pressure has the effect of removing any air which i8 ; trapped between the various plies of the panel. After reduction of pressure the temperature of the panel is raised, also under partlal vacuum to 80C to reach a pre-bonding stage of the panel After the "pre-bonding"
operation the bonding operation is performed in the classical manner at a pressure of 15 kg./cm2 and at a temperature of 130C. The panel thus formed may be placed in a frame very easily and i6 very advantageous in case of a fire. Indeed, $t has been found that such a panel keeps its mechanical stability and its flame-proof properties for 45 minutes, It should be noted that on the advent of fire the layers 2 of hydrated sodium silicate are converted to an anhydrous sodlum silicate having an opaque porous form.
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f , ~(~49912 ~ en a fire screening panel according to tne preserl~ examplc ls subjected to tlle ac~lon of fire on one of its sheel~ faces, the layer of hydrated sodium sllicate applied to the sheet close3t to the flre is converted 'GO an opaque porous fire screening barrier of an~iydrous sodium silicate. This anhydrous barrier is somewhat thicker than the hydrated layer from which it was formed, and is a very effective ~arrler against infra-red radiation. During the course of the conversion, the 1~ bound water is driven off and thus contributes to a limitation of the temperature increase in that layer.
During this phase-the plastic membrane helps to make the temperature uniform across the whole area of the panel, and any local llhot spots" in the firstly converted layer are reflected in larger hot zones in the second layer.
When this first layer is completely dehydrated the other layer of hydrated sodium silicate is in turn converted to form an opaque porous barrier of anhydrous sodium silicate.
~0 These phenomena enable t~e face of the fire screening panel which is not directly subJected to the action of fire to be m~intained at an acceptable temperature for an increased period of time In fact it has been found that when the fire screening panel i5 arranged in a furnace wall the following results are achieved:
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~ ~049912 Temper~ture on outer Temperature face of fire ~creening Time within furnace panel 15 minutes 725C 100C
.~ 30 minutes 825C lOO~C
9~0C 200C

The panel has a high degree of mechanical stabllity during and after conversion of its barrier forming layers :;~ In a variation of the embodiment shown ln figure 1, use was made of glass sheets 1,1 which had been sub~ected to a chemical tempering treatment involv-lng a di~usion of ions into the glass from a contacting medium. This chemical tempering is an exchange of sodium : ions from surface layers of the treated sheets by Potassium ions from the contacting medium which comprises a bath of molten Potas~ium nitrate maintained ak a temperature of 47~C. The result obtained from the point of view of thermal insulation, mechanical stabllity and ~; e~fectiveness as a ~lame- and fume-proof barrier were . 20 analogous to those obtained with the fire screening panel described above. However, this modification has ~: a greater resistance to thermal shock during the first few minutes of a fire than does the panel described above.
In a second modification for use in situations ~: 25 where there is only a very slight fire risk on one side of the partition, the sheet of glass 1 to be directed .

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10~99~2 towards ~hat slde is replaced by a sheet of plastic material. Again, the results obtained ~rom the point of view of resistance to fire were similar to those given above, In a third modification, a fire screening panel was constructed exactly as described at the beginning of this example, except that the layers 2 of hydrated sodium silicate were formed to a thickness of 0,2 mm instead of 2.5 mm. From the point of view of fire resistance, this modification is slightly less effective than the panels described above However, this panel does have the advantage of increased trans-parency.
, In yet another modification, a fire screening s 15 panel was constructed as described above, except that the polyvinyl butyral membrane was replaced by a membrane of polyvinyl chloride. Changing the membrane in this way had no effect on the fire resistance of the panel.

The embodiment s'nown in figure 2 is similar to that shown in and described with reference to figure 1, except that it incorporates an additional layer of barrier forming material 2 and an additional plastic membrane 3. The central layer of barrier forming material 2 was formed as a layer on one of the membranes 3, and .

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the panel was assembled by a method similar to that described ~lith reference to figure 1.
In tilis embodiment the glaS3 sheets 1 were of soda-lime glass 3mm thick~ The layers 2 of hydrated sodium sillcate were each 2.5mm thick and each plastic membrane 3 had a thickness of o.76 mm.
This embodiment of fire screening glazing panel can also easily be placed in a frame. It ulll be appreciated that from the point of view of fire resistance, this panel is better than that of Example 1 because of the additional thickness o~ barrier forming material.

; To form the panel shown in Figure 3, two sheets of glass 1,1 were each coated on one ~ide with a protective stratum 4 o~ zirconium oxide 500 Angstrom units thick, The zirconium oxide coating was formed ln known manner by pyrolysis of a solution in alcohol which had been sprayed through an atomizing nozzle onto a sheet of , 20 - glass heated to 550C. The solution used comprised denatured ethyl alcohol containing 150 gr/litre of zirconium tetrachloride to which was added 10% by volume o~ acetylacetone, The solution was used unheated.
,- The coated side of each sheet 1 was then ~- 25 covered with a heat convertible layer 2 of hydrated ,. . . .

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sodium silicate. In an actual example~ protectively coated glass sheets 1, each 4 mm thick, were covered wlth heat convertible layers 2.5 mm thick by applying a solution of ~Iydrated sodium silicate to the coated sides of tlle sheets and then ventilating the sodium silicate with warm air by means of a fan to drive off unbound . water.
The sodium silicate solution applied had the following properties: ;
! 10 Proportion by Weight SiO2 = 3.4 Na20 ' Viscosity 200 centipoises r/ Specific gravity 37 to 40 Baumé

The sodium silicate solution was applied and then dried ~or 8 period o~ 12 hours at 30C in an atmospherc having a relative humidity of 35~, m e . coated sheets were then assembled on opposite sides of a layer of Q urethane membrane 3 and the plies bonded together to form a laminate. m e bonding temperature . was kept below 100C in order to obviate risk of con-verting hydrated sodium silicate to anhydrous sodium :
silicate, The degree o~ fire resistance given by this panel was similar to the results shown in Example 1.
In addition, the panel describe~ in the present Example has the further advantage of maintaining , .

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it6 optical properties until the advent of fire, even for a pr~l~nged period In particular, i~ has been found that a panel incorporating such protective coat-ings does not lose its transparency after prolonged periods I-t has been observed that a reduction in tr&nsparency will ta~e place in tl,e absence o~ protective strata because of ~he interaction between hydrate~ sod~um silicate and the glass sheets.
As a modification of the embodiment shown in Figure 3, use ~as made of glass sheets 1 which had previousl~ been sub~ected to a c'nemical tempering treatment involving the exchange of sodium ions from the glass ~ith potassium ions ~rom a contacting medium.
The use of tempered glass shee~s gave the panel an increased resistance to breakage due to thermal shock.
In another modification, the sheets of glass 1,1 ~ere replaced by sheets of vitro-crystalline material, and this also gave good results.

~ne embodiment sho~m in Figure 4 is similar to that described in Example 3, except that it incorporates an additlonal layer of barrier forming m~terial 2, and an additional plastics membrane 3. The central layer o~
barrier ~orming material 2 was formed as a layer on one f the plastic membranes 3, and the panel was assembled by a method similar to that described in Example 3.
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Tlle thicknesses of the varlous plies of the panel were the same as those in Xxample 3.
It will be appreciated that because o~ the additional heat convertible layer 2, this panel gave a greater degree o~ ~ire-resistance than the panel described i in EXample 3.
In another em~odiment, the zirconium oxide protective coatings 4 of Figure 4 were replaced by '~,A coatings of indium oxide each 400 Angstrom units thick, These coatings were formed in a known manner, by spraying ;
a solution o~ ind~um chloride through an auto~zing nozzle onto hot sheets of glass where the indium chloride was converted to indium oxide by pyrolysis. This ., .
modification also had very good fire resisting properties.

'~ In Figure 1, two sheets of glass 1,1 were each coated on one side with a layer 2 of hydrated sodium aluminum sulphate. In an actual example, glass sheets 5 ' each ~ mm thick weie each coated with a layer 2.5 mm ;
;~ 20 thick by applying wet hydrated sodium aluminum sulphate to the sheets and then ventilating the coatings with warm air by means of a ~an to drive off unbound water. The ~/l coated glass sheets were then assembled on opposite sides of a stratum of urethane and the assembly was ~s 25 subjected to pressure and heat to polymerize the urethane ~' :; .
$
... .

, ~ .. .. .. . . .. . . . .... . . . . .

s :: : .,.

to form a polyurethane membrane 3 and bond the coated glass sheets together to form a laminate. The bonding temperature was kept below 80~C in order not to convert the hydrated sodium aluminum sulphate to an anhydrous , 5 material. ~nen the fire resistance of this panel was tested, the results achieved were similar to those set out in Example 1 In a variatlon of tllis em~odiment, use was made of glass sheets 1 which had been subJec~ed to a chemical tempering treatment involvin~ the diffusion of s~ potassium ions into the glass from a contacting medium in exchange for sodium ions from the glass.
In another embodiment for use in situations where there is only a very slight fire risk on one side of a partition, the sheet of glass 1 to be directed towards that side was replaced by a sheet of plastic material In a third embodiment, the t~lo glass sheets 1,1 were replaced by sheets of opaque vitrocrystalline material.
Similar results were achieved by these varian~
panels.

A panel was constructed as shown in ~igure 2 in a manner similar to that described in Example 5, ., f s 10499~2 "
except that it incorporated an addltion~l layer 2 Or hydrated sodium alumlrlum sulphate and an additional plas~ic me~.brane 3. The central layer o~ barrier ~orming material 2 was formed as a layer on one of ~he urethane str~ta after that stratum had been formed on a layer 2 of barrier ~orming material deposited on a structural ply 1, but before polymerization there~f, and the panel ~las assembled by a method similar to that described ln Example 5, The two glass sheets were each 4 mm thick, and the three heat convertible layers each had a thickness;
of 2.5 mm. This panel had a greater fire resistance . than the panel of Example 5.

A ~ire-screening panel as schematically shown in Figure 3 was made comprising two glass shee~s 1,1, two heat convertible layers 2 of hydrated sodium aluminate, . a membrane 3 of polyvinyl butyral, and two protective . strat~ 4 o~ acrylic resin The sheets 1 were each of soda-lime glass 4 mm in thickness. They were each placed substantially horizontally, and a pre-polymerized liquid was applied to a depth of 100 microns on their upper surfaces, The pre-polymerized liquid was formed by co-polymerization ; o~ acrylic acid and methyl acrylate and contained 5~
.~. 25 by weight Or methacryloxypropyltrimethoxysilane in order '. ' ~ -28-.;, .
to give increased adhesion to the glass, The treated sheets wer~ then heated to 60C to obtain protective strata of acrylic re~in by polymerization.
A layer 1 mm in thickness o~ hydrated sodium aluminate wa~ then deposited onto the protected face of ;~ each sheet of glass. The hydrated sodium aluminate whiell had been applied in solution was then dried in a current of warm air. When the layers were dry, they were assembled on either side o~ a membrane 3 of poly-vinyl butyral o.76 mm thlck, and the a~sembly was bonded together to form a laminate by the method described ;, in Example 1, except that care was taken to ensure that the bondlng temperature did not rise above 120C in order to avoid risk of converting the sodium aluminate to an anhydrous material Substantially identical panels have also been made by a modified method. As above, each glass sheet was given a 10~ micron coating of the same pre-polymerized liquid, but instead of heating the sheets at this stage, a 1 mm layer o~ hydrated sodium aluminate was applied to one o~ the sheets and dried, A plast~c membrane 0.76 mm thick was laid over this dried layer, and a second layer o~ hydrated sodium aluminate was laid on the membrane j to a th~ckness of 1 mm and then dried with warm air.
. 25 This second layer was then assembled to the coated ~ace ~,,`' ~' ~

:.

. .

10499~2 :

of the other glass sheet and the assembly was bonded together by the method of Example 1, the bondin~
temperature again not being allowed to exceed 120C.
At thls temperature and pressure, the prepolymerized liquid polymerizes to form acrylie resin protective strata bonding the heat convertible layers to the glass sheets, and the heat convertible layers are themselves bonded together firmly via the intervenlng membrane of polyvinyl butyral.
! 1~ In another embodiment, the acrylic resin protective strata 4 were replaced by protective strata of polyvinyl butyral, each o.76 mm thick.
In further modifications, the layers of hydrated sodium aluminate were replaced respectively by potassium aluminate, sodium plumbate, potassium plumbate, sodlum stannate and potassium stannate, all in hydrated form.
In yet f~rther modifications, each heat convertible layer was composed of a different barrier forming materia].
The glazing panels described in this Example have and maintain good optical properties, and have fire resistance characteristics similar to the panels described in Example 3 .i' EXAMPLE ~
., x A ~ire screening panel was made comprising t~o ~ sheets 1,1 (see Figure 3) of transparent vitrocrystalline ., .

:.

~ ~' . ~

10~991~

material Or known cornposition, t~10 heat convertlble layers 2 Or hydrated potassium aluminum sulphate each 0 5 mm thick, a membrane 3 o~ polyvinyl butyral ~.76 mm in thickness, and two protective coatin~s 1~ of anhydrous aluminum pllosphate each 5~ Angstrom unlts thick. The vitrocrystalline sheets were each 4 mm thick The anhydr~us aluminum phosphate protective strata were formed as follows A solution in alcohol of one mole of anllydrous aluminum chloride an~ one mole of anhydrous phosphoric acid was placed in a bath and , each sheet was dipped therein The sheets were arranged vertically and withdrawn from the bath at a speed of 75 cm/minute in that position. One side of each sheet was then wiped, and the sheets were placed in a furnace and heated to 403C. Under these conditions, the alcohol evaporates to leave a coating of anhydrous aluminum phosphate on the unwiped side of each sheet.
A solution of potassium aluminum sulphate is then applied to the sheets 1 on top o~ the protective strata 4 to form heat convertible layers 2. This solution is made by dissolving the potassium aluminum sulphate in ; distilled water and then heating the solution to evaporate i some of the water and obtain a viscous liquid which can easily be spread on the vitrocrystalline sheets. The heat convertible layers are dried in warm air currents and are assembled face to face via an intervening membrane 3 ~i :

", .. ,~ . , ,' .

~049912 o~ polyvinyl butyral 0.76 mm thick, and the assembly is bonded together, It has been found th~t the optical properties o~ this panel are maintained during the course of time ~ince the said protective strata serve substantially to prevent interaction between the vitrocrystalline material and the pota8sium aluminum sulphate, The fire resistance properties of this panel are similar to those of the panels of Example 7, EX~LE ~
A fire screening glazing panel as shown in figure 3 was formed from two sheets 1,1 of transparent vitrocrystalline material each 4 mm in thickness, two heat convertible layers 2 of hydrated sodium borate each 1 mm in thickness, a membrane 3 of polyvinyl butyral 0,7~ -mm thick and a protective coating 4 on the face of each sheet 1 which carrled the heat convertible layer, The heat convertlble layers 4 were of æirconium oxide and were each deposited to a thickness of 350 Angstrom units by the technique given above in example 3, The sodium borate layers 2 were deposited on the zirconium oxlde coatings 4 on the sheets 1 using a saturated solution of sodium borate. The layers thus obtained were dried in currents o~ warm air so as to drive off excess water, , -32 104~91Z
~ nother embodiment a ~ire screening glazing panel was made whlch was similar to that described immediately above except that the sodium borate layers 2 were replaced by layers of hydrated sodium silicate each 2,5 mm thick, The h~drated sodium silicate layers were applied by the technique described in example 1.
It was found that the optical properties of these panels were maintained during the course of time since the zirconium oxide protective strata served substant~ally to prevent interaction between the vitrocrystalllne material and the hydrated sodium borate or hydrated sodium silicate, The fire resistance properties of these panels were good, A ~ire resistant glazing panel, as shown in figure 3 was made comprising two sheets 1 of soda-lime ; glass, two heat convertible layers of hydrated aluminum phosphate each 1.5 mm in thickness, a membrane 3 of polyvinyl butyral ~,76 mm thick and two protective strata 4 of titanium oxide which were each 400 Angstrom units thick, The glass sheets were each 4 mm thick.
The titanium oxide protective strata were deposited by the well known vacuum evaporation technique, ` 25 ' ' ., .

... .

: -, ,' ` ., The heat convertible layers of hydrated aluminum phosphate were formed as follows: a 3,5 molar aqueous solution of aluminum phosphate obtained as the reaction product of solutions of hydrated aluminum chlorlde and phosphoric acid was applied onto the sur~ace~ of ~he glass sheets 1 bearing titanium oxide coatings. The ;i hydrated aluminum phosphate layers were then dried in currents of warm air, A~ter drying, the panel was ; assembled according to the method described in example 1.
~, 10 rne optical properties of this panel were maintained during the course of time and the fire resistance properties were good, As another variation, a similar fire screen-ing vitreous panel was made in which the tltanium oxide i 15 coatings were replaced by tin oxide coatings each 500 Angstrom units thick, These co&tings were applied in the classical manner using a solution of tin chloride and the well known hydrolysis process. ~e optical and fire resistance properties of this modification were similar to those of the panel first described in this example, r .: A fire screening glazing panel, as shown in figure 1 was m~de comprising two sheets 1,1 o~ soda-lime i 25 glass each 4 mm thick3 two heat convertible layers 2 ., , .. , ~ . . ..
.',, ~ , 104ggl2 of hydrated sodium phosphate each 5 ~m thick, and a membrane 3 of polyvinyl butyral which was 0.76 mm in thickness.
The layers 2 o~ hydrated sodium phosphate were obtained by apply~n~ an aqueous solution o~ sodium phosphate on to the glass sheets, and the sheets ~rere then heated to 10~C in order to drive of~ the free water ~lithout~ o~ course, converting the hydrated sodium phosphate to anhydrous material.
After cooling, the sheets were assembled and ;
their respective heat convertible layers were bonded together on either side of a membrane o~ polyvinyl butyral, using a method similar to that described in example 1, except that the rnaximum bonding temperature was maintained below 103C.
This panel had extremQly good fire resLstance properties.
A6 a variation, a similar panel was made in which the heat convertible layers o~ hydrated sodium phosphate were replaced by layers o~ hydrated potassium ; phosphate each 2 mm thick This panel also had good fire resistance properties.

; EXAMPLE 12 Modified glazing panels were made correspond-ing to those described in examples 3, 4 and 7 to 1~, - except that in these modifications no protective strata . ;, ' .

:
were presen'~ e results obteined from the point of view of fire resistance were substan~ially ldentical to similar panels which did include protective strata as described.
-~ 5 The cost of manufscture of these modified panels i8 somewhat less than thst of otherwise similar panels incorporating protective strata, but it will be appreciated that these modified panel6 tend to undergo a deterioration in their optical properties and, in particular, in their transparencies during the course of time as a result of interaction between the barrier forming material and the vitreous sheets of the panels This interaction is greatly inhibited and, in some cases, ~; substantially ellminated by the presence of the protective ` 15 strata.
The use o~ heat convertible layers o~ aluminum ph?sphate is particularly advantageous in the absence of a protective strata, since, when converted by heat, - this material bonds itself very s~rongly to a vitreous `~ 20 sheet to which it is applied This enables the panel to maintain its efficiency, even if a vitreous sheet of the panel should be broken (as by therrnal shock) since the broken fragments can be retained in position by their adherence to the converted layer.

/

, ~0499~
EXA~IPIE 13 ~n opaque fire screening glazlng panel, such as is schematically shown ~1 Figure 5, was made compris-ing a panel identical in all respects with the glazing ' 5 panel described in example 1 which was bonded to a ~ mm thick ~heet 5 o~ polyurethane via an intervening layer 6 of polyvinyl butyral o,76 mm in thickness, The fire resistance properties of this composite panel were generally similar to those set forth in e~ample 1, Although the invention has been herein . shown and described in what is conceived to be the most practical and pref-erred embodiments, it is recognized ! that departures may be made therefrom within the scope of the invention which is not to be limited to details disclosed but is to be accorded the full scope of the claims so as to embrace any and all equivalent structures - ond methods, , 20 ~, .~
~,.' ~,.

.,.
. -37 t

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fire screening panel comprising a first structural ply formed by a vitroues sheet and at least one other structural ply formed by a vitreous or plastic sheet characterized in that there is present at least one plastic membrane having on opposite sides thereof a layer composed at least in part of a material comprising a hydrated metal salt which when sufficiently heated forms a solid porous or cellular body forming a thermally insulating barrier said barrier forming layers and said plastic membrane being sandwiched between said first and other structural ply.

2. A panel as recited in claim 1 wherein said panel is light-transmitting.

3. A panel as recited in claim 1 wherein said hydrated metal salt is selected from the group consisting of aluminates, plumbates, stannates, alums, borates, phosphates, and alkali metal silicates.

4. A panel as recited in claim 1 further comprising a protective stratum between said first structural ply and said barrier forming material for inhibiting interaction between said barrier forming material and said first ply, the protective stratum being selected from the group consisting of anhydrous metal compound coatings deposited onto said first structural ply and sheets of substantially water impervious plastic.

5. A panel as recited in claim 4 wherein said barrier forming material is selected from the group consisting of alums, borates, and alkali metal silicates, and wherein said protective stratum is selected from the group consisting of zirconium oxide and anhydrous aluminum phosphate.

6. A panel as recited in claim 2 wherein said at least one plastic membrane is composed of polyvinyl butyral.

7. A panel as recited in claim 2 wherein said panel comprises two structural plies, each ply consisting of a vitreous sheet and each providing an external face of said panel.

8. A panel as recited in claim 2 wherein said panel is a laminate whose plies are bonded together in face-to-face relationship.

9. A panel as recited in claim 5 wherein a protective stratum is provided between each vitreous structural ply of said panel and an adjacent layer of barrier forming material.

10. A panel as recited in claim 9 wherein said plastic protective stratum is polyvinyl butyral.

11. A panel as recited in claim 5 wherein said coating is between 100 and 1000 Angstrom units thick.

12. A panel as recited in claim 5 wherein said layers of barrier forming material are each between 0.1 and 8 mm thick.

13. A panel as recited in claim 1 wherein said layers of barrier forming material are each between 0.1 and 8 mm thick.

14. A panel as recited in claim 13 wherein at least one of said barrier forming layers is between 0.1 and 0.5 mm thick.

15. A panel as recited in claim 1 wherein said plastic membrane is composed of polyvinyl butyral.

16. A panel as recited in claim 1 wherein said plastic membrane is composed of polyurethane.

17. A panel as recited in claim 5 wherein said protective stratum is composed of polyurethane.

18. A panel as recited in claim 1 wherein at least one vitreous structural ply of said panel has been tempered.

19. A panel as recited in claim 18 wherein said tempered ply has been chemically tempered.

20. A panel as recited in claim 1 wherein said panel comprises two structural plies, each ply consisting of a vitreous sheet and each providing an external face of said panel.

21. A panel as recited in claim 1 wherein said panel is a laminate whose plies are bonded together in face-to-face relationship.

22. A method of forming a laminated fire-screening glazing panel comprising a first structural ply formed by a vitreous sheet and at least one other structural ply formed by a vitreous or plastic sheet comprising the steps of a) applying onto one face of said first ply a layer composed at least in part of material comprising a hydrated metal salt which when sufficiently heated forms a solid porous or cellular body forming a thermally insulating barrier, b) applying another said layer to another structural ply, c) assembling said layered plies on opposite sides of a plastic membrane with said applied layers adjacent thereto, and d) subjecting said assembly to heat and pressure to bond said coated plies and said plastic membrane together to form a laminate.

23. A method as recited in claim 22 wherein said barrier forming material is an hydrated metal salt selected from the group consisting of aluminates, plumbates, stannates, alums, borates, phosphates, and alkali metal silicates, said method comprising the further steps of applying said barrier forming layer as an aqueous solution and drying said solution before assembly of said panel.

24. A method as recited in claim 23 comprising the further step of forming a protective stratum on the face of said vitreous ply adjacent said barrier forming material layer before said barrier forming layer is applied thereto, said protective stratum inhibiting interaction between said barrier forming material and said vitreous ply.

25. A method as recited in claim 22 comprising the further step of forming a protective stratum on the face of said vitreous ply adjacent said barrier forming material layer before said barrier forming layer is applied thereto, said protective stratum inhibiting interaction between said barrier forming material and said vitreous ply, said protective stratum being selected from the group consisting of anhydrous metal compound coatings deposited onto said first structural ply and sheets of substantially water impervious plastic.

26. A method as recited in claim 25 wherein said deposi-tion is performed by pyrolysis.

27. A method as recited in claim 25 wherein said deposi-tion is performed by hydrolysis.

28. A method as recited in claim 25 wherein said coating is formed to a thickness of between 100 and 1000 Angstrom units.

29. A method as recited in claim 25 wherein said protec-tive membrane plastic sheet and said plastic membrane, said plastic membrane being formed of an organic monomer, are bonded together in situ when subjected to said heat and pressure.

30. A method as recited in claim 22 wherein said barrier forming material layers are formed to a thickness of between 0.1 and 8 mm.

31. A method as recited in claim 30 wherein at least one of said barrier forming layers is formed to a thickness of between 0.1 and 0.5 mm.

32. A method as recited in claim 22 wherein at least one of said barrier forming layers is formed to a thickness of between 0.1 and 0.5 mm.

33. A fire screening glazing panel comprising:
- a first structural ply formed by a vitreous sheet, - a second structural ply formed by a vitreous or plastic sheet;
- means for distributing heat uniformly from said first structural ply to said second structural ply upon one of said plies being subjected to heat, said means comprising a plastic membrane; and - a layer on each side of said plastic membrane, each layer comprising a material which is convertible to form a thermally insulating barrier of porous or cellular structure when said panel is subjected to sufficient heat, such as when said panel is subjected to a fire or the like, said heat-convertible barrier forming material being an hydrated metal salt selected from the group consisting of aluminates, plumbates, stannates, alums, borates, alkali metal silicates, and phosphates, said plastic membrane with a layer of heat-converti-ble material on each side thereof being sandwiched between said first and second plies and each of said layers of barrier form-ing material being between 0.1 and 8 mm thick.

34. A panel as claimed in claim 4 wherein said barrier forming material comprises hydrated aluminium phosphate, and wherein said protective stratum is selected from the group consisting of titanium oxide, zirconium oxide, tin oxide and anhydrous aluminum phosphate.