MAN-MADE VITREOUS FIBRE PRODUCTS AND THEIR USE IN FIRE PROTECTION SYSTEMS

Abstract: A fire and high temperature protection product is provided which comprises an air laid web of mineral fibres through which is substantially uniformly distributed a particulate endothermic material which has a mean particle size above 5 mu m and is bonded to the mineral fibres of the web and is a material which is a carbonate and/or hydrate and which is heat stable at up to 200 DEG C and decomposes endothermically at a temperature above 200 DEG C.

Description: MAN-MADE VITREOUS FIBRE PRODUCTS AND THEIR USE IN FIRE PROTECTION SYSTEMS This invention relates to man-made vitreous fibre (MMVF) products which are constructed to be useful for fire protection. Many fire protection products depend, at least in part, on the endothermic properties of a component in the product to provide fire protection. For instance gypsum is a calcium sulphate hydrate. If a high temperature flame is applied to one surface of a gypsum board, the heated gypsum decomposes with absorption of heat and liberates water. Accordingly, a fire front will gradually transfer through the thickness of the board, with the temperature on the side distant from the flame being maintained at 100°C or less. Since the effectiveness of a product made using an endothermic material is proportional, inter alia, to the amount of the endothermic material, it is desirable for the product to have a high concentration of the endothermic material. For instance a gypsum board generally consists almost entirely of gypsum. Unfortunately such materials are physically very weak. It is proposed in CH 382060 to include some endothermic materials in an MMVF product. A product is mentioned which allegedly contains 25 to 30 % by weight glass fibres and 70 to 75 % by weight Kieselguhr bonded into the fibres by a phenolic binder. Apparently it is made by introducing Kieselguhr into a preformed web. It is difficult to introduce inorganic particulate material into a preformed MMVF product in a satisfactory manner. For instance, if the inorganic additive is sufficiently finely ground it may be possible to inject the powder into the web but it will then dust out of the web again. It is also possible to impregnate the web with an aqueous slurry of the finely ground powder, but the web then has to be dried and this is uneconomic. So far as we are aware, the products described in CH 382060 have not been commercialised successfully. This is probably due, in part, to the fact that the endothermic material was always very finely ground so as to allow its introduction into the preformed web, and was not adequately bonded into the web. Many of the bonding agents which are conveniently used for MMVF products require being heated to a high temperature, for instance 200°C or higher, in order to cure them. Endothermic materials which have an endothermic decomposition temperature well below 200°C (such as Kieselguhr) are therefore likely to undergo decomposition during curing. It would be desirable to be able to combine the known properties of an air laid web of MMV fibres with the fire protection properties of endothermic materials without incurring the manufacturing difficulties and the other disadvantages of known products, such as described in CH 382060. A fire protection material according to the invention comprises an air laid web of MMVF fibres through which is substantially uniformly distributed a particulate endothermic material, wherein the endothermic material has a particle size above 5 μm and is bonded to the MMV fibres of the web and is a material which is a carbonate or a hydrate and the particles are heat stable at up to 200°C and decompose endother ically at a temperature above 200°C. The particulate endothermic material must be heat stable at temperatures up to 200°C. That is, it must not undergo substantial endothermic decomposition at temperatures of 200°C or less, preferably 240°C or less. Heat stability at temperatures up to 200°C may be obtained in various ways. For instance the material chosen may be such that it undergoes no endothermic decomposition at temperatures below 200°C. In this way it can be subjected to high temperatures but retain its ability to decompose endothermically when the fire protection product is in use. Alternatively particulate materials may be used wherein the particles tend to begin endothermic decomposition below 200°C but which are provided in such a form that they do not undergo substantial decomposition at temperatures up to 200°C. In this way they also retain their ability to decompose endothermically when the fire protection product is in use. Such materials may undergo small amounts of decomposition at temperatures of up to 200°C, but they do not undergo substantial decomposition and thus are heat stable. Preferred materials liberate carbon dioxide and/or water of crystallisation only at temperatures above 200°C. Suitable materials are magnesium hydroxide, calcite (calcium carbonate) , dolomite, siderite, aragonite, magnesite, brucite, magnesium carbonate, barium carbonate, barium hydroxide, ferric hydroxide, ferrous hydroxide, pyrite, and silicon compounds with water of crystallisation which do not liberate any water at temperatures up to 200°C. The particle size of the endothermic material must be above 5 μm. Accordingly normally 90% by weight of the particles are above 5 μm. Preferably the particle size is at least 90 % above 10 μm, more preferably at least 90% above 15μm. For materials which undergo no decomposition below 200°C, it can be at least 90 % below 200 μm, for instance at least 90 % below 100 μm. Expressed as mean particle sizes, the preferred ranges are 5 or 10 to lOOμm, preferably 10 to 70μm, most preferably 15 to 50μm. A mean particle size of around 15 to 50 μm, often around 35 μm, is often satisfactory. Alternative materials are those which tend to liberate carbon dioxide and/or (in particular) water of crystallisation at temperatures below 200°C, but which are provided in a form such that liberation of carbon dioxide and/or water is minimised. For instance, materials which have a temperature of decomposition of between 150°C and 200°C, for instance from 180 to 200°C, may be provided in the form of especially coarse particles. We find surprisingly that materials of this type in the form of coarse particles can withstand temperatures up to 200°C, and often up to 240°C, without substantial decomposition by release of water of crystallisation and/or carbon dioxide. Preferred materials of this type are those which liberate water of crystallisation, for instance aluminium hydroxide, which if used in the form of fine grains loses all its water of crystallisation at around 185°C. For these materials suitable mean particle sizes are at least lOOμm, often at least 500μm, and even up to 3mm, such as from 0.5 to 1.5mm. Materials which liberate carbon dioxide at temperatures below 200°C when in fine-grain form can also be provided in coarse-grain form to render them heat stable at temperatures up to 200°C in the same way as for materials which release water of crystallisation. One preferred class of materials is the class of those which liberate carbon dioxide, such as calcium carbonate, and especially such materials which liberate carbon dioxide at temperatures above 400°C and preferably above 600°C. For instance calcium carbonate liberates carbon dioxide endothermically at temperatures in the range 700 to 1000°C. Another class of materials is the class of crystalline materials which liberate water of hydration at temperatures of above 200°C, preferably above 240°C, for instance 270 to 370°C or higher. Materials, or mixtures of materials, which have different endothermic reactions at two or more temperatures are very desirable since it spreads fire resistance over a large scale. For instance a mixture of hydrate and carbonate is desirable for this reason. It is desirable that the material, or each material in the mixture, should have as high an endothermic energy as possible. Some materials which might have a high endothermic energy are excluded because they decompose completely at below 200°C. A particularly preferred material is magnesium hydroxide since it has high endothermic energy and is stable at 200°C and is conveniently available in coarse particle size. The particle size of the endothermic material should preferably be as coarse as is reasonably possible so as to allow good bonding of the endothermic material into the web without need for the use of a large amount of bonding agent. For instance the surface area of 1 gram of a 1 μm filler typically is around 50 times the surface area of 1 gram of a 50 μm filler. Thus a 50 μm filler requires very much less binder, for satisfactory binding properties, than a 1 μm filler. In the invention, by using relatively coarse endothermic particulate material, it is possible to maintain good bonding using an amount of binder which is not unacceptably more than the amount which would be used in the absence of the endothermic material. For instance the dry weight of binder is typically in the range 1 to 3 % in the conventional MMVF product and in the invention good bonding can be achieved when the amount of binder is about the same or not more than 50 to 100 % more, for instance within the range 2 to 6 % by weight of the product. The invention is particularly useful when the particulate material is abrasive, but it can be used for softer, less abrasive particulate materials. It is necessary that the MMVF product should be bonded into the web in order that there is little or no dusting of the product from the web during transport and handling. Very small amounts of dusting are acceptable since the product can be covered on each surface by a fire resistant and temperature stable covering such as aluminium foil or other coating, but excessive dusting is unacceptable. A suitable test for determining whether or not it is satisfactorily bonded is that described by Schneider et al, Ann. Occup. Hyq. , Vol. 37, No. 6, pp 631-644, 1993. The binder which is used for bonding the endothermic material into the MMVF product can be any of the binders conventionally used for bonding MMVF products. The amount of binder is generally in the range 2 to 6 % by weight of the product. The web of MMVF fibres must be an air laid web as it is impracticable to wet lay it and then to dry it. As is well known, an air laid MMVF web has (even after compression) a much lower density than a wet laid product. For instance the air laid web (excluding the endothermic material, which also acts as a filler) will always have a density below 300kg/m , often below 250 kg/m . Impregnating a preformed fibre web with the endothermic material will give a non-uniform or otherwise unsatisfactory product, with more endothermic material adjacent the side of entry than elsewhere. Impregnation with an aqueous slurry is wasteful of energy because of the need to dry the material. The air laid web may be formed by applying mineral melt to a rotating fiberising rotor thereby throwing the melt from the periphery as fibres and forming a substantially annular cloud of the fibres, spraying binder into the annular cloud of fibres, carrying the fibres axially from the rotor towards a collector surface, mixing the endothermic material with the fibres and collecting the mixture of fibres and endothermic material on the collecting surface as a web. This web may be the web of the final fire resistant product or, more usually, the initial web is laminated upon itself and is then compressed to form a batt, and it may be this compressed batt which is used as the web in the fire resistant product of the invention. In order that the coarse, particulate, endothermic material is bonded into the web, it is preferred that the particulate material is coated with binder before it is mixed with the MMVF fibres. A preferred way of making the product of the invention comprises forming the annular cloud of MMVF fibres as described above, coating the endothermic particulate material with binder and mixing the coated particulate material into the cloud, and collecting the resultant mixture on a collector surface as a web. Additional binder is usually sprayed into the cloud to increase fibre-fibre bonding. A preferred way of coating the particulate endothermic material with binder is to form a slurry of the particulate material in aqueous binder, in which event the particulate material can then be introduced into the annular cloud by spraying. In practice, the slurry will normally contain at least 5 %, by weight of the slurry, of the particulate endothermic material but the amount is often above 10 % or even 20 %. It can be as much as 60 % but is usually not more than about 40 %. It is desirable for the specific gravity of the slurry to be high since this increases the penetration of the slurry into the annular cloud. The specific gravity can be at least 1.0 and is usually at least 1.1, preferably at least 1.2 and usually at least 1.3 and often at least 1.4. It is usually below 2, generally below 1.7. In order to facilitate spraying, it is desirable that the slurry should be reasonably stable against settlement and the aqueous binder therefore preferably includes a dispersion stabiliser that will inhibit settling. The dispersion stabiliser may be any suitable viscosifier, but preferably it is a colloidal material since the presence of colloidal material in the aqueous phase can both inhibit settlement of the filler and adjust the rheology of the slurry so as to facilitate spraying. Preferably the dispersion stabiliser is a clay and thus the slurry is preferably a slurry of particulate endothermic material having a size above 5 μm, often above 10 μm and preferably above 30μm in an aqueous dispersion of clay particles typically having a size below 5 μm often below 3 μm. The amount of clay or other colloidal material in the slurry is typically in the range 0.5 to 10% based on the weight of slurry, often up to 7%, generally 1.5 to 5 %. The amount of clay, if used, in the air laid product is generally in the range 0.5 to 3 %. The clay can tend to have a binding effect and thus may serve not only as a dispersion stabiliser but also as part or all of the binder. Preferably, however, organic resin binder is also used. A suitable method for spraying such a slurry into the annular cloud so as to form a bonded air laid web is described in our British application 9524608.0, corresponding to our international application filed even date herewith Reference PRL03608WO. Suitable apparatus for use in this method is described in British Application 9524607.0, corresponding to our international application filed even date herewith Reference 60/3487/03. In another aspect of the invention, a fire protection product comprises a bonded web of MMV fibres in which is distributed an endothermic material selected from magnesium hydroxide and carbonates that decompose endothermically at above 200°C. Preferably the web contains magnesium hydroxide in an amount of at least 5%, more preferably at least 10% by weight of the total material. The endothermic material may be introduced in any convenient size and method and may or may not be distributed uniformly and may or may not be bonded. Preferably it is distributed uniformly and is bonded and is in the form of particles of size above 5 μm, often above lOμm. In all aspects of the invention, the amount of endothermic material is usually in the range 5 to 50%, e.g. 25 to 30%. The fire resistant products of the invention can be in the form of slabs, mats, pipes or granulate. When in the form of slabs they may be provided in the form of a laminate between steel sheets. Products of this type are particularly suitable for use as fire doors. The fibrous products can have a density in the range of 10 to 300 kg/m . The mineral fibres of the product can be made from glass, rock, stone, or slag but preferably they are made from rock, stone or slag because of the extreme fire resistance of these fibres. The spinner can be of the spinning cup type described in EP 530843 or of the Downey type as described in US 2944284 and US 3343933, but preferably the rotor is mounted about a substantially horizontal axis and has a solid periphery and is constructed to receive melt applied onto the periphery and to throw mineral fibres off the periphery. Most preferably it is a cascade spinner containing 2, 3 or 4 such rotors. A suitable cascade spinner is described in, for instance, WO92/06047. When the endothermic particulate material is being applied by spraying a slurry, the slurry may be sprayed coaxially from, for instance, the last fiberising rotor and/or the penultimate fiberising rotor and if desired binder may be sprayed coaxially from the other fiberising rotors. Accordingly the annular cloud of fibres into which the slurry is laid will not be a true annulus but will instead merely extend forward from the outermost parts of the cascade. The following is an example of the invention. In this example, a spinner is used as illustrated in the accompanying drawings in which Figure 1 shows a cross-section through a rotor which forms part of the spinner. Figure 2 shows a front view of a further rotor according to the invention showing an alternative liquid flow outlet. Figure 1 shows a solid rotor 1 of the type used in a cascade spinner mounted on a rotatable shaft 3. Fixed to the rotor is a liquid distribution means 16 having a distribution surface 11. The substantially frustoconical surface 11 is a concave surface containing a plurality of grooves 18, of which six are illustrated. The distribution surface has a short edge 12 and a long edge 14, the long edge 14 being forward of the short edge 12. The long edge 14 is at a radius 0.6 R, where R is the radius of the rotor. The rotor 1 is supported, on the rotating shaft 3, by roller bearings 32. The non-rotatable liquid flow duct 5 is supported on bearings 30, usually roller bearings, between the rotating shaft 3 and the non-rotatable liquid flow duct 5. The non-rotatable liquid flow duct 5 leads into and is fixed to the liquid flow outlet 7, which is also non-rotatable. This has two (or more) radially extending discharge orifices. The radially extending discharge orifices may be inclined rearwardly at an angle of 10-45° so as to ensure discharged liquid meets the distribution surface at the smallest possible radius. In use a suspension of particulate solids in an aqueous phase is supplied (supply means not shown) to the liquid flow duct 5 which extends through the rotatable shaft 3, and into the liquid flow outlet 7. The suspension then passes through the orifices 9. The partially atomised suspension passes across an air gap in the direction of the arrows and onto the distribution surface 11. The rapid spinning of the liquid distribution means 16 induces radial outward movement of the suspension, guided by the grooves 18, to the end points 20 of the grooves at the edge 14. From these end points the suspension is flung in atomised form from the distribution surface radially outwards and forward of the rotor. If any suspension fails to travel radially outwards along the grooves 18, but tends to leak back into the apparatus, it passes along the inlet channel 28 into the rotating annular chamber 24. Rotation of the chamber induces the suspension to move to the outer wall of the chamber, from where it flows along outlet channel 26 onto the distribution surface at its short edge. A seal 34 is positioned between the chamber 24 and the roller bearings 30. Leakage into other regions of the apparatus is thus avoided. Concurrently, melt is applied to the periphery 22 of the rotor 1 which is spinning rapidly and flinging the melt from the periphery as fibres. The fibres are blown forward by conventional air supply means (not shown) in an annular cloud. As the fibres are blown forward they are met by the atomised suspension from the liquid distribution means. The suspension and additives it contains penetrate the annular cloud and coat the fibres. The fibres are then collected as a web containing uniformly distributed additive on a collector in conventional manner. The web may be subjected to cross- lapping to form a batt, and the product may be compressed and heat cured in conventional manner. Figure 2 shows an alternative construction for the liquid flow outlet 7. In this construction it is in the form of a slot covering around 135° of the possible 360°. Liquid additive exits the liquid flow duct 5 through the slot 36 and is passed to the liquid distribution surface 11. The liquid additive flows over the region 38. The "spiral" type path of the liquid arises as a result of the rapid rotation of the distribution surface in a clockwise direction. In other embodiments rotation can be in an anticlockwise direction. The liquid additive is thus flung from the long edge 14 of the distribution surface in a substantially upward direction over around 135° of the circumference of the distribution surface. Example 1 A suspension of resol formaldehyde binder in water is placed in a pulper. A slurry having specific gravity above 1.1 is produced by mixing with the binder dispersion particulate magnesium hydroxide having a mean size of 35μm. The slurry is included in fibres at the point of fibre formation by means of the apparatus and process of Figure 1 described above. A slab product is produced from the resulting fibres. The same process is carried out without the use of magnesium hydroxide fire retardant material. Both the fire resistant slab according to the invention (slab A) and the conventional slab (slab B) were subjected to a standard fire test according to ISO 834. Results are shown in Table 1 below. These illustrate the temperature on the cold side of the slab after a certain time. The results shown indicate the gradual increase in temperature on the cold side of the slab as a result of heat passing through the slab. In some products a very rapid increase in temperature followed by a very rapid decrease in temperature can be observed. This is due to combustion of binder. This combustion is minimised in slab A of the invention. As can be seen from the results below the time for the temperature on the cold side of the slab to rise to 190°C or greater is more than three times as long with slab A than with slab B, showing the improved fire and heat resistance of the products of the invention. Poor results are also obtained when magnesium hydroxide is used having an average particle size of 2 μm. in

Claims: CLAIMS 1. A fire and high temperature protection product which comprises an air laid web of MMV fibres through which is substantially uniformly distributed a particulate endothermic material characterised in that the particulate endothermic material has a mean particle size above 5 μm and is bonded to the MMV fibres of the web and is a material which is a carbonate and/or a hydrate and which is heat stable at up to 200°C and decomposes endothermically at a temperature above 200°C. 2. A product according to claim 1 in which the endothermic material is selected from magnesium hydroxide and carbonates which decompose endothermically at a temperature above 200°C. 3. A fire protection product which comprises a bonded web of MMV fibres in which is distributed a particulate endothermic material selected from magnesium hydroxide and carbonates that decompose endothermically at above 200°C. 4. A product according to any preceding claim which includes particulate magnesium hydroxide in an amount of at least 5% by weight of the product. 5. A product according to any preceding claim in which the endothermic material has a mean particle size of 10 to 500 μm, preferably 10 to 100 μm. 6. A product according to any of claims 1 to 4 in which the endothermic material has a mean particle size of from 0.5 to 3 mm. 7. A product according to claim 6 in which the endothermic material is aluminium hydroxide. 8. A product according to any preceding claim in which the amount of particulate endothermic material is from 5 to 50% based on the weight of the product. 9. A product according to any preceding claim additionally containing colloidal clay. 10. A product according to any preceding claim having a density of at least lOkg/m . 11. A product according to any preceding claim in which the air laid web, in the absence of the endothermic material, has a density below 300kg/m . 12. A product according to any preceding claim made by applying mineral melt to a rotating fiberising rotor and thereby throwing the melt from the periphery of the rotor as fibres and forming a substantially annular cloud of fibres, coating the particulate endothermic material with binder and mixing the coated material into the cloud of fibres and collecting the mixture as an air laid bonded web and curing the binder. 13. A product according to claim 12 in which the particulate material is coated with binder by dispersing it as a slurry in aqueous binder and spraying the slurry into the annular cloud of primary fibres.

Inventors: CLAUSEN ANDERS ULF, CLAUSEN, ANDERS, ULF
Applicants: CLAUSEN ANDERS ULF, ROCKWOOL INT, CLAUSEN, ANDERS, ULF, ROCKWOOL INTERNATIONAL A/S
Application year: 1996
Main classification: C03B37
IPC codes: C03B37, C03C1, C03C25