DESCRIPTION

This invention concerns lightweight panels which are insulating and have low smoke and toxic fume emissions under fire conditions.

Within public transportation the aspects of weight and fire safety have become major issues. Fires in underground railway systems are disastrous reminders of the need to limit spread of flame and emission of smoke and toxic fumes.

The shipping industry has upto now been required by international rules to use non-combustible materials for fire resisting divisions. Therefore, steel bulkheads, which in a fire situation could glow cherry red, have had to be used.

With the development of the new IMO Code of Safety for high speed craft there are now provisions for introducing new materials in this rapidly growing category of vessels. Conventional ferries and cruise ships also have weight problems relating to damage stability requirements. With the introduction of aluminium into superstructures of modern ferries, a method of protecting the construction from meltdown in a fire is essential.

Panel systems are known which performed to desired fire criteria but are unfortunately comparatively heavy. Some are made of steel and concrete whilst others are laminates of resin pre- impregnated glass cloth where multi-layers are needed to achieve the desired standard.

Another common form of fire barrier has a wooden or metal framework containing pads or a lamella of rock wool and faced with plaster board. Phenolic resin foam has very good insulation qualities but cannot last more than an A30 test without additional protection. Such protection usually adds considerably to the weight and there is a problem with fixing a front face to the foam to avoid delamination during a fire situation.

An object of this invention is to provide lightweight panels which are insulating and have low smoke and toxic fume emissions under fire conditions.

According to this invention there is provided a lightweight panel comprising at least one layer of an insulating foam material and at least one layer of an adhesive having or treated to have fire resistant properties.

The preferred adhesive for use in the invention is one that is capable of holding together char formed from the panel in a fire situation. Suitable adhesives

for use in the invention may include sodium silicate based adhesives and resorcinol phenol formaldehyde based adhesives.

The adhesive used in the invention preferably contains one or more fire resistant materials, such as one or more frits, mica, zinc borate, alumina trihydrate, hydrated calcium magnesium carbonate, hydrated calcium carbonate and zinc oxide.

For a sodium silicate adhesive it is preferable to include a substance that will convert silicate to silica under fire conditions. Such a substance may be selected from zinc oxide, china clay, ball clay kaolin and silica itself.

Frits are generally required to hold the panels together under fire conditions. Sodium silicate intumesces at about 460°C and turns to powder, whereas the frit or frits can be chosen to melt and fuse at a lower temperature so as to hold the panels together. Mica may be added to extend the performance of frits. A typical powder blend is for sodium silicate adhesive, for example, as follows:

Parts by Weight Hydrated calcium magnesium carbonate and/or alumina trihydrate 20-40 especially 30 Hydrated calcium carbonate 0-5

One or more frits 10-50 especially 20

Mica 10-40 especially 10

Zinc borate 5-30 especially 10

Zinc Oxide 10-50

The powder mix is preferably added to the adhesive in an amount of from 5 to 30 parts by weight per 100 parts by weight of adhesive. When alumina trihydrate and hydrated magnesium calcium carbonate are used together their weight ratio is preferably 1:2.

For resorcinol phenol formaldehyde based adhesives preferably only one or more frits and/or mica are added. Ammonium polyphosphate may be added to resorcinol based adhesives on a fire resisting material.

The panels of the invention may include one or more layers of other material, such as, for example, aluminium, glass cloth, glass needle mat, ceramic paper and stainless steel.

In one preferred embodiment of the invention a panel comprises a layer of phenolic foam faced on its intended cool side with a phenolic resin pre-impregnated glass cloth as a balancing material. The side of the panel which will face the flames is preferably faced with a sandwich of glass cloth, basalt and glass fibre felt and glass cloth. Alternatively a backing cloth with needle fibres can be used instead of the felt. The facing sandwich is preferably impregnated with phenolic resin, which preferably contains powdered fire retardant

materials as mentioned hereinbefore, such as one or more frits. The felt may be pre-impregnated with adhesive, also containing fire resistant powder materials as mentioned hereinbefore, such as one or more frits. The adhesive impregnated felt is preferably dried and used b ^e tween phenolic resin impregnated glass cloths.

Another alternative preferred panel according to the invention comprises relatively thin layers of phenolic resin foam bonded together with the adhesive. In a fire situation the layer nearest the heat chars and that char, held together with the activated adhesive, protects the second layer and so on. The adhesive preferably contains fire resistant powder materials as mentioned hereinbefore. Such panels may be faced with aluminium treated on its outer face with the powder/adhesive mix also containing chopped glass strand or glass cloth soaked in the adhesive mix. An alternative preferred facing for panels of the invention is rigidised stainless steel foil. Panels according to the invention may be capped on their edges with a lightweight channel formed from a suitable material such as pre-impregnated phenolic resin glass clot! to protect the phenolic foam from direct contact with flame. The channels are preferably formed to give an interlocking effect when the panels are assembled to form a fire barrier.

The panels may be further locked together with a system of phenolic resin pultrusions or dough mouldings in the form of pins or dowels and clips. A preferred method includes pultruded or dough moulded pins which pick up a high heat resistant steel wire within the fixing method and tension the panels together, both vertically and horizontally. Phenolic resin used for this purpose preferably contains fire retardant powder mixes of the type mentioned above to prolong the life of the part in fire conditions.

The use of phenolic resin containing a powder blend of fire resistant materials and char promoters in a pultrusion, dough moulding or other suitable method of production gives a product which does not substantially transmit heat and which substantially retains its ability to hold the panels together during a fire.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 shows a section through a joint formed between two panels of the invention;

Figure 2 shows an individual panel as used in figure 1;

Figure 3 shows an alternative panel construction; Figure 4 shows yet another panel according to the invention;

Figure 5 shows a system for fixing panels of the type shown in Figure 4 to a supporting structure;

Figure 6 shows yet a further panel of the invention; and Figure 7 shows a further example of a panel of the invention;

Figure 8 shows a joint formed between panels of figure 7;

Figure 9 shows yet a further example of a panel of the invention.

Referring to Figure 1 of the accompanying drawings, a typical support member comprising a vertical I-beam 1 with a jig drilled hole 2 is shown for supporting a pair of panels 3 connected end to end. The panels are connected by means of a pin 10 having an annular groove 11 at each end. The grooves 11 accept split rings 13 which snap in place to lock the panel to the I-beam after the pin has been pushed through pre- drilled holes in both the panel and the I-beam. The pin has a split 14 at its leading end which picks up a loop in a tensioning wire 9. The loop is pushed through the holes and can then be tightened by rotating the pin using a screwdriver in pinhead slot 12.

The construction of the panels 3 is shown in Figure 2. The panels comprise a phenolic resin pre- impregnated cloth 15 on the intended cool face of the

panel, a phenolic foam sheet 16 having adhered to each end high density phenolic resin foam shapes 17 covered in foamed phenolic resin pre-impregnated glass cloth 18 and a sandwich of pre-impregnated glass cloth 19 and felt or needle mat 20 on its front face. The panels are assembled under heat and pressure. Layers of the panel may be adhered together using a sodium silicate based adhesive.

The wires 9 with loops on either end of the panel are shown. It should be understood that the horizontal edges of the panels are treated in the same way to create a picture frame which is locked vertically and horizontally to its neighbour. The end forms, as individual moldings, can be fixed to walls, floors and ceilings to engage with the matching part moulded to the panel.

The same construction with the exception of the interlocking mouldings which are replaced by a peripheral frame of U-shaped channels capping the panel, can be used as a door blank, or as a panel, partition or bulk-head filling. The felt sandwich would in most cases be applied to both sides of the lightweight phenolic foam in these cases.

An alternative to the felt can be effected by bonding together thin layers of phenolic foam with sodium silicate based adhesive. The phenolic resin

and/or sodium silicate used in the panels of Figures 1 and 2 may include one or more fire retardant powder materials, such as one or more frits, mica, zinc borate, alumina trihydrate, hydrated calcium magnesium carbonate, ammonium polyphosphate and zincoxide. In a fire situation the layer nearest the heat chars and the char held together with the activated adhesive protects the second layer and so on.

An alternative panel construction that has been found to be effective is described with reference to figure 3 of the accompanying drawings. A phenolic pre- impregnated glass cloth 30 which has had a powder mix added comprising ultracarb, one or more frits, mica and ammonium polyphosphate or zinc borate is converted to a two or more sheet laminate as a backing layer by heat and pressure. This layer is adhered to the back face of a layer of phenolic foam 32, which may have a glass tissue or glass mesh reinforced aluminium foil on its surface. The front face of the panel, being that which is exposed to view and to the risk of fire is covered with a glass needle mat 34 which has been impregnated with sodium silicate and fire retardant powder mix as described above and compressed in a heated plattern press to approximately 25% of its original thickness. The sheet 34 is rigid and is adhered to the substrate using a sodium silicate adhesive containing a powder mix

comprising ultracarb, one or more frits, mica and ammonium polyphosphate. Another layer 36 of the phenolic resin pre-impregnated glass cloth may be used as a front face when adhered to the needle mat 34 and painted using a non-toxic, low smoke, nil-spread flame paint, such as that containing CEEPREE (trade mark) and produced by H Marcel Guest.

Strips 38 cut from the compressed panel are adhered to the edges of the phenolic foam 32 to act as a protective layer. An alternative construction uses the phenolic resin impregnated needle mat 36 as the back face laminate instead of the phenolic glass cloth layer 30. Turning to figure 4 of the drawings, a panel 40 has needle mat 42 on all faces and edges of the phenolic foam 44. This construction makes a core material either singly or adhered together in multiples which are suitable for inclusion in a metal construction 46 for doors, partitions and cold storage walls.

When the panels are mounted, butted edge to edge, edging strips 42 expand to twice their original size in a fire situation and seal the joint between the panels.

Turning to Figure 5 of the drawings, the method for joining such panels together or to a structure is to use stainless steel screws 48 through silicone rubber or butadiende rubber washers at the base of a pre-drilled hole through a reinforced area 52 of the backing sheet.

A plug 54 made from a rod of either phenolic resin and powder mix pultrusion or from the sodium silicate powders and glass mix and moulded, is pushed into the hole as a fire protective cover. This method allows the panels to be disassembled at will to gain access to services which may run in the cavity between the protection and the structure.

As shown in Figure 6, another panel 60 has overlapping lightweight aluminium mesh 62 incorporated in the phenolic foam as part of the manufacturing process. The foam can either be phenolic or a mechanical foam made from a mix of powders comprising ultracarb, one or frits, mica and ammonium polyphosphate or zinc borate and sodium silicate. The mesh would be used to provide strength and for fixing through the exposed holes around the periphery of the panels. The channel formed by this method between boards can be filled using a silicone rubber or butadiene rubber extrusion as a deformable removable seal. The rubber would be filled by the powder mix disclosed to stop spread of flame and to promote a healthy char.

Referring to Figures 7 and 8 of the accompanying drawings, it has been found by fire test to BS47 parts 20-22 and A60, that it is possible to extend the life and, therefore, the insulation qualities of phenolic resin foam in lightweight firesafe panels by using an

adhesive which is composed of sodium silicate, one or more frits, mica, zinc borate and zinc oxide, the powders being at 25 parts by weight each to 500 parts by weight of the sodium silicate. This adhesive or a resorcinol phenolic resin adhesive substituted in the same proportion as the sodium silicate, is used to laminate thin layers of phenolic foam together to form a panel where the front faces can form a char in a fire situation. As the heat penetrates it reaches the next layer of adhesive and that in turn helps to promote a cohesive layer of char to protect the remaining laminations. It is possible to calculate the number of layers needed to satisfy the various criteria regarding insulation for a set period of time. This method has the advantage of nil-spread of flame, low smoke production and low toxic fume emission, those fumes produced being mainly carbon dioxide which is used to stop spread of flame.

The panel has a back face 100 composed of a pressed laminate of two pre-impregnated glass cloth sheets. The resin used being phenolic, sometimes of the aqueous emulsion type, containing a powder mix of the type specified. The back face is adhered to a phenolic foam layer 104 by means of an adhesive layer 102 either based on sodium silicate or phenolic resin. It has been found that a resorcinol phenol formaldehyde with the

powder specified added to the hardener powder is effective. The sodium silicate with powders is also effective and, in particular, does not give off smoke and toxic fumes. The panel has further layers of phenolic foam and adhesive and is finished with an aluminium sheet 106 formed to aid fixing or alternatively a laminated phenolic pre-impregnated glass cloth sheet or stainless steel foil. The panels are fixed together using non-heat conductive fixings 110 based on phenolic pultrusions or dough mouldings to fix the recessed edge to the back support 106 and a non-heat conducting fixing 112 to fix the front lip to the recessed edge. Silicone or butadiene filled with the fire resistant powder mix, applied as an extrusion L- shaped sealing bead 114 is fitted between abutting panel edges. The material used for items 110, 112 and 114 will expand during a fire because of the action of the powder additives. The expansion is in the order of twice the original thickness and is sufficient to fill the gap between panels and stop fire penetration.

If aluminium is chosen as the front face, ie the face that would be exposed to fire, then, since the melt temperature is around 650°C, it is desirable to raise the melt temperature to at least 950°C or beyond, which is the temperature reached at the end of an A60 fire test. It has been found that two coats of the above

described sodium silicate adhesive and fire resistant powder mix additionally with chopped glass strand or glass cloth on the front face of the aluminium decorated with a CEEPREE containing polyepoxide paint can have this effect.

Similarly, adhering a phenolic resin and powder pre-impregnated laminate as described on the front face, can have the same effect. A combination of the sodium silicate adhesive and the phenolic laminate can be made easier by the introduction of a silica paper or glass tissue or cloth on the inner face of the laminate, the object being to achieve a bond between the inner surface of the additional material and the inner surface of the laminate during its manufacturing cycle, without complete encapsulation. Thus, a mechanical bond can be made using sodium silicate and powder adhesive, which material has the effect of making even paper non¬ flammable.

Finally in Figure 9 of the accompanying drawings panels 200 are shown fixed together and to a substrate represented by 202. Each panel 200 has successively from its hidden face a layer of phenolic foam 204, a layer of sodium silicate adhesive 206, a layer of phenolic foam 208, a layer of sodium silicate adhesive 210, a layer of phenolic foam 212 and a layer of rigidised stainless steel foil 214 (thickness

approximately 0.1mm). The end face of each panel also has a coating of intumescent material 215.

The sodium silicate adhesive used contains one or more fire retardant additives, such as one or more frits, mica, zinc borate, zinc oxide and alumina trihydrate, hydrated magnesium calcium carborate or hydrated calcium carborate. The phenolic foam layers may contain one or more fire retardant materials as aforesaid. In order for the panels 200 to be easily removable a fixing method has been chosen as illustrated. Top-hat section strips 216, 218 with crowns inboard are positioned between ends of adjacent panels. The inner strip 216 is joined to the substrate 202 by screws 220 and the outer strip 218 is joined to the inner strip 216 by screws 224. The screw heads 224 are hidden by a snap-in cover strip 226. The intumescent material 215 is provided to protect these fixings under fire conditions by swelling and preventing flame spread between the panels. Removal of the outer strips 218 at each end of a panel, allows it to be removed easily.