A building material

Abstract

A composite material is provided for use as a damp proof course or cavity tray system. The material comprises a first layer of a sheet of glass fibre matting material, an aluminium foil layer bonded a

Description

Field of the Invention The present invention relates to a building material with improved fire-resistant properties. The material is suitable for use as part of a cavity tray, and also as a damp-proof course. Background to the Invention Systems are developed in order to ensure any water or other liquids in the cavity of a double-skin wall are expelled via the walls of the building under the action of capillary forces. Once within the building, the moisture can cause damage to materials and also cause mould to grow in the interior of the buildings, and hence its removal is important. A significant moisture problem can arise due to the presence of a cavity wall in a building. Many buildings are constructed having a cavity wall around the outside, which cavity wall comprises an inner and an outer leaf which are tied together. This has the property of increasing the heat retention of the building by providing an air barrier between the outside of the building and the interior. The cavity wall also serves to reduce water penetration into the building. Nevertheless water can still cross between the leaves at certain points within the building. As examples of such points, then roof abutments, above airbricks, doors, windows and concrete lintels can be cited. To prevent this water ingress, cavity trays are installed which bridge between the leaves directing water from the inner leaf, downwards to the outer leaf. In recent years, following a series of devastating fires in high rise buildings, it has been recognised that the fire-resistant properties of cavity trays need to be improved as the conventional materials utilised were shown to catch fire under the conditions experienced. As a further example of a means of prevention of ingress of water into a building, then a damp-proof course is typically included. A damp-proof course is in effect a water impermeable layer provided between 2 layers of bricks in a wall, usually close to ground level, to prevent water from rising, primarily between these 2 layers, predominantly by capillary action. The invention disclosed herein is suitable for use as a damp-proof course or a cavity tray in double skin walls to improve the fire-resistant properties of materials from which trays are formed. Summary of the Invention According to a first aspect of the invention, there is provided a composite material, said composite material comprising a first layer of sheet glass fibre matting material having a first surface and second surface, a second aluminium foil layer having a first and second surface, the first surface of the aluminium foil layer being bonded to the first surface of the first layer of the glass fibre matting material by a fire-retardant adhesive, an outer polymeric layer coating the second surface of the aluminium foil layer. This provides protection of the aluminium from the effects of any aqueous alkaline conditions, which may be present. Preferably, the outer polymeric layer is a polyvinylchloride (PVC). Alternatively preferably, the outer polymeric layer is a silica layer. Further alternatively preferably, the polymer is a polyethylene terephthalate (PET). The glass fibre matting material is preferably coated with a polyurethane (PU) coating. The composite material is a flexible material which can be rolled up for transportation and storage and is of increased fire-resistance. Preferably, the density of the outer layer is from 16 - 24 grammes / m2 (gsm), further preferably 20gsm. The density of the glass fibre matting material is preferably from 250 - 400 gsm, further preferably 270 gsm. This provides the composite laminar material with sufficient flexibility to enable the material to be supplied in rolled up form, typically around 25m in length when unrolled, and also to be formed, such as by cutting with a conventional knife, into a conformation suitable for the building being constructed. Preferably, the second surface of the first layer of glass fibre matting material is an in use lower surface. Preferably, the first surface of the aluminium foil layer is coated with a polymer selected from Polyvinylchloride, Silica, Polyethylene terephthalate, and further preferably Polyvinylchloride. Preferably, the first and second surfaces of the aluminium foil layer are coated with a layer of polyethyleneterephthalate. Further preferably, the density of the layer is 3gsm. According to a second aspect of the invention, there is provided a method of manufacture of a composite material, the method comprising the steps of selecting a first layer of a sheet of glass fibre matting material having a first and second surface, selecting an aluminium foil layer having a first and second surface, bonding the first surface of the aluminium foil layer to the first surface of the glass fibre matting material by a fire-retardant adhesive, coating the second surface of the aluminium foil layer with a polyvinylchloride layer. According to a third aspect of the invention, there is provided a method of manufacture of a composite material, the method comprising the steps of selecting a first outer layer of a sheet of glass fibre matting material having a first and second surface, selecting an aluminium foil layer having a first and second surface coating the second surface of the aluminium foil layer with a polyvinylchloride layer, bonding the first surface of the aluminium foil layer to the first surface of the first layer of the glass fibre matting material by means of a fire-retardant adhesive. Brief Description of the Drawings The invention is now described with reference to the accompanying drawings which illustrate, by way of example only, three embodiments of a composite material. In the drawings: Figures la, lb illustrate a first embodiment of a composite material Figure 2 is a perspective view of a second embodiment of a composite material; Figure 3 illustrates the separate layers within the composite material of Figure 2; and Figure 4 illustrates a third embodiment of composite material. Detailed Description of the Invention The materials utilised as, for example, a cavity tray are either rigid or flexible materials which resist the transport of water through the body of the material. In use, and as described with reference to a cavity tray, the cavity tray material is typically incorporated between adjacent horizontal layers of bricks, and held in position using the mortar utilised to construct the rest of the wall. The cavity tray is fixed to the inner wall using stainless steel fixing strips bolted to the vapour membrane of the inner wall. The present invention provides a mat, of layered construction, and including an aluminium foil layer. Due to the use conditions of the mat in contact with mortar, a coating is provided to the surface of the aluminium layer exposed to the mortar. Mortar contains chloride ions and typically has a pH, whilst still in the liquid form, of from 7.0 - 9.2, both of which conditions result in corrosion of aluminium. The corrosion is typically in the form of pitting which firstly can weaken the aluminium and secondly can lead to pathways being formed in the aluminium via which water can travel, so penetrating the mat. A first embodiment of material is disclosed in Figures la and lb. The first embodiment shown, has a glass fibre matting layer 10, of 270 gsm (grams per square metre) density. Typically, the density of the glass fibre matting layer is from 250 - 400 gsm especially preferably ~270gsm and has a thickness of from 0.2 -0.3mm. In order to reduce water absorption into the glass fibre matting layer 10, a polymeric coating 11 is applied to the in-use outer, usually the in-use lower surface 12 of the glass fibre matting layer 10. In a further embodiment, the polymeric coating is a polyurethane (PU) protective layer. It is anticipated that, given the porous nature of the glass fibre, the coating soaks, at least partially, into the body of the glass fibre by means of a wicking process. Sufficient coating is added to prevent water take up by the glass fibre in use. An aluminium foil layer 13 of thickness around 1pm, is secured to the surface 14 of the glass fibre matting layer 10, by means of a PU adhesive layer 15, preferably being a fire-retardant adhesive. In a preferred embodiment, both of the main surfaces of the aluminium foil layer 13 are coated with a polyvinylchloride (PVC) material, 16, 17 to reduce corrosion of the aluminium and provide a further waterproof barrier. The PVC layers 16,17 typically have a density of 3gsm, + / -15%. In a further embodiment only one layer, equivalent to layer 16, is included. In an alternative embodiment only the surface of the aluminium foil bonded to the glass fibre matting layer is coated with the polymeric layer. In a further preferred embodiment, the glass fibre is coated and / or has absorbed therein a waterproof material such as that marketed under the trade name Nanoflam (RTM), to prevent water ingress into the body of the fibre glass. In further embodiment, the polymer coating one or both of the surfaces of the aluminium foil is a polyethylene terephthalate. Referring to Figures 2 and 3, these illustrate the layered structure of a mat in accordance with a second embodiment of the invention, generally referenced 20. In broad terms, the mat 20 comprises a first glass fibre matting layer D. The glass fibre mat D is of a density of approximately 290 gsm. The higher density of the glass fibre provides for good shear strength of the layer. The glass fibre material has a fireproof rating of Al. An aluminium foil layer B is secured across one surface 21 of the glass fibre matting layer by means of a fire-retardant adhesive C having a fireproof rating of Al. In order to protect the aluminium foil layer B from attack by the alkalinity and the chloride ions within the mortar, the outer surface 22 of the aluminium foil layer B is coated in this second embodiment by a silica layer A of thickness 5-50 pm, preferably approximately 20 pm, and a density of from 16 - 24 gsm or preferably 20 gsm. The silica layer is hydrophobic and so acts to repel water from the aluminium layer. Optionally, the coating is on both surfaces of the aluminium foil layer B. A woven glass fibre matting material is selected to form the mat D, having a density of from 250 - 400 gsm and thickness of from 0.2 -0.3mm. A hotmelt adhesive is applied across one surface of the glass fibre matting material. The adhesive can either be added as a film across the surface or alternatively in discrete areas. An aluminium foil layer is then laid over the glass fibre matting material, sandwiching the adhesive therebetween. Heat is applied to melt the adhesive, with pressure applied (for example by rolling the fibre matting material and the aluminium foil layers together) to force the aluminium and the glass fibre matting material together, spreading the melted adhesive across both surfaces and into intimate contact therewith. As an example of an adhesive can be cited Kleiberit 701.5 PUR hotmelt adhesive in respect of which a curing temperature of 110°C is utilised. A suspension of silica in a volatile carrier liquid is sprayed onto the free surface of the aluminium foil and allowed to air cool under fan extraction, with the liquid evaporating to leave behind a layer of silica adhered to the aluminium foil at a density typically 16 - 24 gsm, preferably approximately 20 gsm. Figure 4 illustrates a third embodiment of a mat. The mat, generally referenced 40, comprises a 2-ply laminate. The mat 40 comprises a glass fibre matting layer 41, treated with a fluorocarbon cross-linker to a density of 5gsm. As an example of a suitable coating material is Archroma's NUVA(RTM) 703. The second layer is an aluminium Iayer44 having a thickness of 50 pm. The aluminium layer 44 is coated with a PET material of density 4gsm, on both sides 43a, 43b. These layers 43a, 43b act to protect the aluminium layer 44 against weathering and corrosion. The glass fibre matting layer 41 is secured to the aluminium layer 44 by a hot-melt fire-retardant adhesive layer 42. As an example of a suitable adhesive can be cited Kleiberit 701.5. In an alternative embodiment the silica layer is applied to the aluminium foil prior to bonding of the foil to the glass fibre mat. Optionally, a polyurethane (PU) can be used in place of silica. The, now laminar, material is cooled and the free surface of the aluminium foil coated with a suspension of silica in a volatile liquid carrier. The temperature is raised and / or the pressure above the laminar material lowered in order to remove the liquid carrier and leave a silica coating on the aluminium foil. As indicated, the silica layer is applied to the aluminium foil layer in the form of a suspension of silica particles in a volatile carrier liquid. The carrier liquid is preferably water or an alcohol of low boiling point or mixture thereof, but other easily volatilised liquids known in the art can also be used. Mixtures of liquids can also be used, including those having vapour pressures higher than the individual components. The liquid carrier is evaporated from the surface of the aluminium layer to leave a layer of adhered silica, typically of thickness around 10 pm. As non-limiting examples of alcohols can be cited, methanol, ethanol, 2-methylpropan-l-ol, isobutanol. As a further non-alcoholic liquid can be cited 2-ethylhexylester. A cavity tray in accordance with the invention was subjected to a combustion test in respect of British Standard EN ISO 1716. The cavity tray was formed of a woven glass fibre cloth of thickness 0.22mm, and having a density of 280gsm (gram per square metre) (or also expressed as 1310.1 kg m-3. An aluminium foil sheet of thickness 50pm was adhered thereto using a polyurethane-based adhesive marketed under the name Kleiberit 701.5 PUR. The adhesive is a thermal hotmelt adhesive having a density as applied of 15gsm. The adhesive also a includes a fire-retardant material known in the art. On testing a first sample, the individual components of the cavity tray had mean combustion values of: woven glass fibre cloth, 0.22MJ kg-1, the adhesive 27.8 MJ kg-1, and the aluminium foil 0.00 MJ kg-1. The material had a mean gross heat of combustion of 1.11MJ kg1. This places the material in Category Al in accordance with BS EN ISO1716. Testing of a second sample in the form of a cavity tray and having a silica layer of density 20 gsm gave mean combustion values of: woven glass fibre cloth, 0.22MJ kg1, the adhesive 27.8 MJ kg1, and the aluminium foil 0.00 MJ kg1. Overall, the material had a mean gross heat of combustion of 1.64 MJ kg-1. This places the material in Category Al in accordance with BS EN ISO1716. The water resistance and mechanical properties of a cavity tray formed from the composite material of the present invention and having a density of ~1470 kg / m3 showed compliance with the requisite British Standards.

Claims

1. A composite material, said composite material comprising a first layer of sheet glass fibre matting material having a first surface and second surface, and a second aluminium foil layer having a first and second surface, the first surface of the aluminium foil layer being bonded to the first surface of the glass fibre matting material by a fire-retardant adhesive, an outer layer coating the second surface of the aluminium foil layer.

2. A composite material according to Claim 1, wherein the outer layer is a polyvinylchloride.

3. A composite material according to Claim 1, wherein the outer layer is a silica layer.

4. A composite material according to Claim 1, wherein the outer layer is a polyethylene terephthalate.

5. A composite material according to any preceding claim, wherein the glass fibre matting material is coated with a polyurethane.

6. A composite material according to Claim 3, wherein the density of the silica layer is from 16 - 24 grammes / m2.

7. A composite material according to Claim 6, wherein the density of the silica layer is approximately 20 grammes / m2.

8. A composite material according to any preceding claim, wherein the density of the glass fibre matting material is from 250 - 400 grammes / m2.

9. A composite material according to Claim 8, wherein the density of the glass fibre matting material is 280 grammes / m2.

10. A composite material according to any preceding claim, wherein the second surface of the glass fibre matting material is an in use lower surface.

11. A composite material according to any preceding claim, wherein the first surface of the aluminium foil layer is coated with a polymer selected from Polyvinylchloride, Silica, Polyethylene terephthalate.

12. A composite material according to claim 12, wherein the first surface of the aluminium foil layer is coated with Polyvinylchloride.

13. A composite material according to any preceding claim, wherein the first and second surfaces of the aluminium foil layer are coated with a layer of polyethyleneterephthalate.

14. A composite material according to claim 13, wherein the density of the layer is 3gsm.

15. A method of manufacture of a composite material, the method comprising the steps of selecting an outer layer of a sheet of glass fibre matting material having a first surface and second surface, selecting an aluminium foil layer having a first and second surface, bonding the first surface of the aluminium foil layer to the first surface of the glass fibre matting material by a fire-retardant adhesive, coating the second surface of the aluminium foil layer with a silica layer.

16. A method of manufacture of a composite material, the method comprising the steps of selecting a first layer of a sheet of glass fibre matting material having a first surface and second surface, selecting an aluminium foil layer having a first and second surface coating the second surface of the aluminium foil layer with a silica layer, bonding the first surface of the aluminium foil layer to the first surface of the glass fibre matting material by means of a fire-retardant adhesive.

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