WO2014111552A1

WO2014111552A1 - Floor panel

Info

Publication number: WO2014111552A1
Application number: PCT/EP2014/050964
Authority: WO
Inventors: Dorte Bartnik JOHANSSON; Kristian Skovgaard Jorgensen; Jesper Rene RASMUSSEN
Original assignee: Rockwool International A/S
Priority date: 2013-01-18
Filing date: 2014-01-17
Publication date: 2014-07-24

Abstract

A floor panel for use in a raised floor system, the panel comprising: a base layer comprising man-made vitreous fibres and binder and having a density of at least 300 kg/m³, such as at least 450 kg/m³, such as around 500 kg/m³; a floor surface tile; and a layer of foam composite material, disposed between the base layer and the floor surface tile, comprising a polymeric foam and man-made vitreous fibres produced with a cascade spinner or a spinning cup, wherein at least 50% by weight of the man-made vitreous fibres present in the foam composite material have a length of less than 100 micrometres.

Description

FLOOR PANEL

Field of the Invention The present invention relates to a floor panel for use in a raised floor system. This type of panel is, in use, supported at its edges by a support system, which raises the floor above its usual level, allowing wires, pipes and the like to trail underneath the raised floor surface. The present invention also relates to a raised floor system and a method for installing a raised floor.

Background to the Invention Raised floors are used in rooms where it is required to have wires or pipes running underneath the floor and where relatively easy access to those wires or pipes is required. A typical example is a server room, where a large number of connecting computer wires are laid under the raised floor, where air conditioning pipes are often also present. Easy access to the pipes and wires is required for purposes of maintenance and for modification of the server system.

As the floor panels are only supported at their edges, they need excellent strength, in particular, bending strength, but also need to be light to ensure that they are easily lifted up (usually with a suction pad) when access to the wiring or pipe system is required.

In some circumstances it is also desirable to provide sound insulation, for example to prevent the sound of the computer server from permeating into the room underneath the server room.

EP1589159 describes an access floor system including a plurality of supports and high rigidity sandwich plates. The sandwich plates have an upper board and a lower board, each preferably made from multi-ply wood, and a reinforcing frame which includes at least one reinforcing member, which is disposed across the central axis of the frame. Sound absorbing material can be inserted between the reinforcing members. Foamed urethane is mentioned as a sound absorbing material, but appears not to contribute to the rigidity of the plate. Summary of the Invention

To achieve the above-mentioned aims, the invention provides a floor panel for use in a raised floor system, the panel comprising:

a base layer comprising man-made vitreous fibres and binder and having a density of at least 300kg/m³, such as at least 450 kg/m³, such as around 500 kg/m³;

a floor surface tile; and

a layer of foam composite material, disposed between the base layer and the floor surface tile, comprising a polymeric foam and man-made vitreous fibres produced with a cascade spinner or a spinning cup, wherein at least 50% by weight of the man-made vitreous fibres present in the foam composite material have a length of less than 100 micrometres.

The invention also provides a raised floor system comprising a support system extending upwards from a floor and a plurality of floor panels as described above, supported at their edges by the support system.

The invention also provides a method of installing a raised floor comprising: providing a support system extending upwards from a floor; and positioning a plurality of floor panels according to the invention on the support system so that the floor panels are supported at their edges by the support system.

The floor panel of the invention has an excellent combination of properties. The base layer provides a high degree of bending strength to ensure that the panel can withstand being walked on in between the points of contact with the support system. The layer of foam composite material adds to the overall bending strength, due to its positioning above the base layer and its high compressive strength. The layer of foam composite material also helps a high overall compressive strength to be achieved, whilst also ensuring that the overall weight of the floor panel is not too high. Both the base layer and the layer of foam composite material have excellent fire resistance, so could help in the containment of a fire beginning within the room.

The floor surface tile is not only of aesthetic importance, but also helps to distribute any loads across the entirety of the layer of foam composite material so that it is protected from damage from sharp objects and the high pressure exerted by the feet of server cabinets, for example.

The foam composite material and the base layer are also helpful in preventing heat from permeating through the floor. This helps any air conditioning or climate control system that is present to function more efficiently. The floor panel also has a high level of sound insulation.

Detailed Description of the Invention

The invention is described below with reference to the accompanying drawings. Figure 1 shows a cross section of a floor panel according to the invention.

Figure 2 shows a cross section of a floor panel according to the invention.

Figure 3 shows a cross section of a raised floor system according to the invention.

Figure 4 is an environmental scanning electron microscope image of a polyurethane foam composite material as used according to the invention.

Figure 1 shows a floor panel 1 for use in a raised floor system. The panel 1 comprises a base layer 2 comprising man-made vitreous fibres and binder and having a density of at least 300 kg/m³. The panel also comprises a floor surface tile 3 and a layer of foam composite material 4 disposed between the base layer 2 and the floor surface tile 3. The foam composite material comprises a polymeric foam and man-made vitreous fibres produced with a cascade spinner or a spinning cup, wherein at least 50% by weight of the man-made vitreous fibres present in the foam composite material have a length less than 100 micrometres. It is described in greater detail below. Also shown in Figure 1 is an optional glass fibre mesh 5, which is disposed on the underside of the base layer 2 on the side of the base layer 2 opposite to the layer of foam composite material 4.

The floor panel 1 is not limited in its dimensions, but preferably has a total area of from 500 to 20000 cm², more preferably from 3000 to 15000 cm². Preferably the floor panel has standard dimensions of about 60 x 120 cm, or of about 60 cm x 60 cm, or about 30 cm x 60 cm, or about 30 cm x 120 cm.

The thickness of the panel 1 is preferably in the range 0.5 cm to 20 cm, more preferably from 2 cm to 7 cm and most preferably from 3 cm to 6 cm. Usually the thickness is about 4-5 cm. In order that the floor panel has sufficient bending strength and rigidity, the base layer 2 comprises man-made vitreous fibres and binder and has a density of at least 300 kg/m³. The man-made vitreous fibres in the base layer 2 can be any suitable fibres such as glass fibres, ceramic fibres or slag fibres, but are preferably stone fibres. Preferably the base layer 2 consists essentially of binder-coated man-made vitreous fibres.

In a more preferred embodiment, the base layer has a density of at least 450 kg/m³ or at least 480 kg/m³ such as around 500 kg/m³. The density of the base layer 2 may also be substantially higher, such as around 600 kg/m³ or even higher such as 1200 kg/m³, depending on the circumstances (i.e., the weight which has to be supported by the floor panel). Preferably, the base layer has a bending strength of at least 7 N/m².

The binder present in the base layer 2 is not limited and could, for example, be selected from phenol formaldehyde binder, urea formaldehyde binder, phenol urea formaldehyde binder, melamine formaldehyde binder, condensation resins, acrylates and other latex compositions, epoxy polymers, sodium silicate, hotmelts of polyurethane, polyethylene, polypropylene and polytetrafluoroethylene polymers. In a particular embodiment, the base layer is produced according to the method set out in International Application PCT/EP201 1/069777. Such plates have a particularly high level of strength.

In order to have good strength, preferably, the base layer 2 has a thickness of at least 3 mm, more preferably at least 5 mm and most preferably at least 10 mm. However, in order to keep the overall weight of the floor panel 1 to a minimum it is preferred that the base layer 2 has a thickness of less than 50 mm, more preferably less than 40 mm.

The base layer 2 can be affixed to the layer of polymeric foam composite material 4 by use of an adhesive, for example. However, it has been found that it is not necessary to use an adhesive if the base layer 2 is positioned during formation of the layer polymeric foam composite material 4. By avoiding the use of adhesive, the floor panel 1 is particularly well suited for automatic production on a production line. Therefore, preferably, there is an intrinsic bond between the base layer 2 and the layer of polymeric foam composite material 4 and no extrinsic fixing means is present.

The layer of polymer foam composite material 4 is formed from a polymeric foam composite material as described below. This layer typically has a thickness of at least 3 mm, preferably at least 5 mm and more preferably at least 10 mm. The thickness is usually less than 50 mm, preferably less than 40 mm.

The layer of polymeric foam composite material 4 is disposed between the base layer 2 and a floor surface tile 3. Usually, as shown in Figure 1 , the layer of polymeric foam composite material will be in direct contact with both the base layer 2 and the floor surface tile 3, but this is not essential. Preferably, however, the layer of polymeric foam composite material 4 is in direct contact with the base layer 2.

The floor surface tile 3 can be of any type known in the art such as carpet tiles, high-pressure laminates, wood, polymer materials, marble, stone and tiles with anti-static finishes. Alternatively the floor surface tile 3 can be cast of cement or similar materials, e.g. cast directly on the panel at production thereof or after laying of the floor panels. Preferably, the floor surface tile is not, however, a tile comprising man-made vitreous fibres and binder and having a density of at least 300 kg/m³. Preferably the floor surface tile 3 is affixed to the layer of polymer foam composite material 4 with an adhesive. Alternatively the floor surface tile could be affixed with tape, glue or mechanical fixing means. The thickness of the floor surface tile 3 is generally between 1 mm and 20 mm, usually between 2 mm and 13 mm, more usually between 3 mm and 8 mm.

Generally, the base layer 2, the floor surface tile 3 and the layer of polymeric foam composite material 4 overlap each other substantially completely.

Also shown in Figure 1 is an optional glass fibre mesh 5 disposed on a face of the base layer 2 opposite from the layer of polymeric foam composite material 4. The glass fibre mesh 5, where present, comprises uni-directional fibres or fibres laid up in two directions, such as mesh or woven of a type known in the art as commercially available from, for example, Textile Technologies Europe Ltd. or Skanda Acoustics Ltd. The glass fibre mesh 5 has good tensile strength in the direction of the fibres and, therefore, when affixed to the underside of the base layer 2 and aligned properly in relation to the forces present can add significantly to the bending strength of the floor panel 1 . Where present, the glass fibre mesh 5 can be affixed to the base layer 2 with an adhesive or by the binder that is present in the base layer 2 itself. The latter can be achieved by curing the binder in the base layer 2 with the glass fibre mesh 5 already in position. In order to provide a secure connection, adding additional binder on the surface of the base layer 2 before curing may be necessary.

Figure 2 shows a preferred embodiment of the floor panel 1 of the invention. The panel comprises a base layer 2, a layer of polymeric foam composite material 4 and a floor surface tile 3 as described above in relation to Figure 1 . The embodiment shown in Figure 2 further comprises an upper layer 6 disposed between the layer of polymeric foam composite material 4 and the floor surface tile 3. The upper layer 6 comprises man-made vitreous fibres and binder and has a density of at least 300 kg/m³.

The man-made vitreous fibres in the upper layer 6 can be any suitable fibres such as glass fibres, ceramic fibres or slag fibres, but are preferably stone fibres. Preferably the upper layer 6 consists essentially of binder-coated man-made vitreous fibres.

In a more preferred embodiment, the upper layer 6 has a density of at least 450 kg/m³ or at least 480 kg/m³ such as around 500 kg/m³. The density of the upper layer 6 may also be substantially higher, such as around 600 kg/m³ or even higher such as 1200 kg/m³, depending on the circumstances (i.e., the weight which has to be supported by the floor panel). Preferably, the upper layer 6 has a bending strength of at least 7 N/m².

The binder present in the upper layer 6 is not limited and could, for example, be selected from phenol formaldehyde binder, urea formaldehyde binder, phenol urea formaldehyde binder, melamine formaldehyde binder, condensation resins, acrylates and other latex compositions, epoxy polymers, sodium silicate, hotmelts of polyurethane, polyethylene, polypropylene and polytetrafluoroethylene polymers.

In a particular embodiment, the base layer is produced according to the method set out in International Application PCT/EP201 1/069777. Such plates have a particularly high level of strength.

In order to have good strength, preferably, the upper layer 6 has a thickness of at least 3 mm, more preferably at least 5 mm and most preferably at least 10 mm. However, in order to keep the overall weight of the floor panel 1 to a minimum it is preferred that the upper layer 6 has a thickness of less than 50 mm, more preferably less than 40 mm.

The upper layer 6 can be affixed to the layer of polymeric foam composite material 4 by use of an adhesive, for example. However, it has been found that it is not necessary to use an adhesive if the upper layer 6 is positioned during formation of the layer polymeric foam composite material 4. By avoiding the use of adhesive, the floor panel 1 is particularly well suited for automatic production on a production line. Therefore, preferably, there is an intrinsic bond between the upper layer 6 and the layer of polymeric foam composite material 4 and no extrinsic fixing means is present.

A glass fibre mesh disposed on a face of the base layer 2 opposite from the layer of polymeric foam composite material 4 is not shown in Figure 2, although it could, of course, be present in this embodiment too.

The panel 1 shown in Figure 2 also comprises a reinforcing sheet 7 embedded within the layer of polymeric foam composite 4. The reinforcing sheet 7 is not essential, but is preferred to add strength to the panel 1 . Preferably the reinforcing sheet 7 is a glass fibre nonwoven sheet.

Figure 3 shows a raised flooring system according to the invention in a cross- section view. The raised floor system comprises a support system extending upwards from a floor 9 and a plurality of floor panels 1 as described above, which are supported by the support system. The floor panels 1 have a base layer 2, a floor surface tile 3 and a layer of polymeric foam composite material 4 disposed between the base layer 2 and the floor surface tile 3. The construction of the floor panel is described above in relation to Figures 1 and 2. In the embodiment shown in Figure 3, the support system comprises a plurality of metallic pillars 8, although any system capable of supporting the panels 1 above the floor 9 can be used. The floor panels 1 are supported at their edges by the pillars 8. This provides an under-floor space 10 in which wiring and piping can be positioned.

The support system preferably has a height of from 10 cm to 35 cm, more preferably from 15 cm to 30 cm. Where the support system is in the form of metallic pillars 8, the floor panels 1 are preferably supported at their corners. Preferably, the pillars 8 have horizontal plates 1 1 at their upper ends. In another preferred embodiment, the metallic pillars 8 are joined to one another at their upper ends by a grid of metallic bars (not shown), which support the floor panels 1 all along their edges.

Usually, the support system is manufactured from steel, although any sufficiently strong material could be used. The raised floor system of the invention could be used in a domestic building, but is particularly useful in an office building and, in particular, in a server room.

Polymeric Foam Composite Material The invention makes use of the polymeric foam composite material described in our earlier application filed on 18 August 201 1 and having the application number EP 1 1 177971 .6 and in our international application PCT/EP2012/066196 filed on 20 August 2012. The disclosure of those applications is incorporated herein by reference.

The polymeric foam composite material used in the present invention can be produced from a foamable composition comprising a foam pre-cursor and man- made vitreous fibres, wherein at least 50% by weight of the man-made vitreous fibres have a length of less than 100 micrometres.

The weight percentage of fibres in the polymeric foam composite material or in the foamable composition above or below a given fibre length is measured with a sieving method. A representative sample of the man-made vitreous fibres is placed on a wire mesh screen of a suitable mesh size (the mesh size being the length and width of a square mesh) in a vibrating apparatus. The mesh size can be tested with a scanning electron microscope according to DIN ISO3310. The upper end of the apparatus is sealed with a lid and vibration is carried out until essentially no further fibres fall through the mesh (approximately 30 mins). If the percentage of fibres above and below a number of different lengths needs to be established, it is possible to place several screens with incrementally increasing mesh sizes on top of one another. The fibres remaining on each screen are then weighed. According to the invention, the man-made vitreous fibres present in the polymeric foam composite must have at least 50% by weight of the fibres with a length less than 100 micrometres as measured by the method above.

By reducing the length of man-made vitreous fibres that are present in the foamable composition and in the polymeric foam composite, a larger quantity of fibres can be included in the foamable composition before an unacceptably high viscosity is reached. As a result, the compressive strength, fire resistance, and in particular the compression modulus of elasticity of the resulting foam can be improved. Previously, it had been thought that ground fibres having such a low length would simply act as a filler, increasing the density of the foam. However, by using mineral fibres with such a high proportion of short fibres, far higher levels of fibres can be incorporated into the foam precursor and the resulting foam. The result of this is that significant increases in the compressive strength and, in particular, the compression modulus of elasticity of the foam can be achieved.

Preferably, the length distribution of the man-made vitreous fibres present in the polymeric foam composite or foamable composition is such that at least 50% by weight of the man-made vitreous fibres have a length of less than 75 micrometres, more preferably less than 65 micrometres.

Preferably, at least 60% by weight of the man-made vitreous fibres present in the polymeric foam composite or foamable composition have a length less than 100 micrometres, more preferably less than 75 micrometres and most preferably less than 65 micrometres.

Generally, the presence of longer man-made vitreous fibres in the polymeric foam composite or foamable composition is found to be a disadvantage in terms of the viscosity of the foamable composition and the ease of mixing. Therefore, it is preferred that at least 80%, or even 85 or 90% of the man-made vitreous fibres present in the polymeric foam composite or foamable composition have a length less than 125 micrometres. Similarly, it is preferred that at least 95%, more preferably at least 97% or 99% by weight of the man-made vitreous fibres present in the polymeric foam composite or foamable composition have a length less than 250 micrometres.

The greatest compressive strength can be achieved when at least 90% by weight of the fibres have a length less than 100 micrometres and at least 75% of the fibres by weight have a length less than 65 micrometres.

Man-made vitreous fibres having the length distribution discussed above have been found generally to sit within the walls of the cells of the foam composite, without penetrating the cells to a significant extent. Therefore, it is believed that a greater percentage by weight of the fibres in the composite contribute to increasing the strength of the composite rather than merely increasing its density.

It is also preferred that at least some of the fibres present in the foam composite material, for example at least 0.5% or at least 1 % by weight, have a length less than 10 micrometres. These very short fibres are thought to be able to act as nucleating agents in the foam formation process. The action of very short fibres as nucleating agents can favour the production of a foam with numerous small cells rather than fewer large cells.

The fibres present in the polymeric foam composite or in the foamable composition can be any type of man-made vitreous fibres, but are preferably stone fibres. In general, stone fibres have a content by weight of oxides as follows:

Si0₂ 25 to 50%, preferably 38 to 48%

Al₂0₃ 12 to 30%, preferably 15 to 28%

Ti02 up to 2%

Fe₂0₃ 2 to 12%

CaO 5 to 30%, preferably 5 to 18% MgO up to 15% preferably 4 to 10%

Na₂0 up to 15%

K₂0 up to 15%

P₂0₅ up to 3%

MnO up to 3%

B₂0₃ up to 3%.

These values are all quoted as oxides, with iron expressed as Fe₂0₃, as is conventional.

An advantage of using fibres of this composition in the polymeric foam composite material, especially in the context of polyurethane foams, is that the significant level of iron and alumina in the fibres can act as a catalyst in formation of the foam. This effect is particularly relevant when at least some of the iron in the fibres is present as ferric iron, as is usual and/or when the level of Al₂0₃ is particularly high such as 15 to 28% or 18 to 23%.

An alternative stone wool composition useful in the invention has oxide contents by weight in the following ranges:

Si0₂ 37 to 42%

Al₂0₃ 18 to 23%

CaO + MgO 34 to 39%

Fe₂O₃ up to 1 %

Na₂O + K₂O up to 3%

Again, the high level of alumina in fibres of this composition can act as a catalyst in the formation of a polyurethane foam. Whilst stone fibres are preferred, the use of glass fibres, slag fibres and ceramic fibres is also possible. The man-made vitreous fibres present in the polymeric foam composite and foamable composition are discontinuous fibres. The term "discontinuous man- made vitreous fibres" is well understood by those skilled in the art. Discontinuous man-made vitreous fibres are, for example, those produced by internal or external centrifugation, for example with a cascade spinner or a spinning cup. Traditionally, fibres produced by these methods have been used for insulation, whilst continuous glass fibres have been used for reinforcement in composites. Continuous fibres (e.g. continuous E glass fibres) are known to be stronger than discontinuous fibres produced by cascade spinning or with a spinning cup (see "Impact of Drawing Stress on the Tensile Strength of Oxide Glass Fibres", J. Am. Ceram. Soc, 93 [10] 3236-3243 (2010)). Nevertheless, it has been found that foam composites comprising short, discontinuous fibres have a compressive strength that is at least comparable with foam composites comprising continuous glass fibres of a similar length. This unexpected level of strength is combined with good fire resistance, a high level of thermal insulation and cost efficient production.

In order to achieve the required length distribution of the fibres, it will usually be necessary for the fibres to be processed further after production with a cascade spinner or a spinning cup. The further processing will usually involve grinding or milling of the fibres for a sufficient time for the required length distribution to be achieved.

Usually, the fibres present in the polymeric foam composite and foamable composition have an average diameter of from 2 to 7 micrometres. Preferably, the fibres have an average diameter of from 2 to 6 micrometres, more preferably the fibres have an average diameter of from 3 to 6 micrometres. Thin fibres as preferred in the invention are believed to provide a higher level of thermal insulation to the composite than thicker fibres, but without a significant reduction in strength as compared with thicker fibres as might be expected. The average fibre diameter is determined for a representative sample by measuring the diameter of at least 200 individual fibres by means of the intercept method and scanning electron microscope or optical microscope (1000x magnification). The foamable composition that can be used to produce the polymeric foam composite comprises a foam precursor and man-made vitreous fibres. The foam precursor is a material that either polymerises (often with another material) to form a polymeric foam or is a polymer that can be expanded with a blowing agent to form a polymeric foam. The composition can be any composition capable of producing a foam on addition of a further component or upon a further processing step being carried out.

Preferred foamable compositions are those capable of producing polyurethane foams. Polyurethane foams are produced by the reaction of the polyol with an isocyanate in the presence of a blowing agent. Therefore, in one embodiment, the foamable composition comprises, in addition to the man-made vitreous fibres, a polyol as the foam precursor. In another embodiment, the foamable composition comprises, in addition to the man-made vitreous fibres, an isocyanate as the foam precursor. In another embodiment, the composition comprises a mixture of an isocyanate and a polyol as the foam precursor.

If the foam precursor is a polyol, then foaming can be induced by adding a further component comprising an isocyanate. If the foam precursor is an isocyanate, foam formation can be induced by the addition of a further component comprising a polyol.

Suitable polyols for use either as the foam precursor or to be added as a further component to the foamable composition to induce foam formation are commercially available polyol mixtures from, for example, Bayer Material Science, BASF or DOW Chemicals. Commercially available polyol compositions are often supplied as a pre-mixed component that comprises polyol and any or all of catalyst(s), flame retardant(s), surfactants and water, the latter which can act as a chemical blowing agent in the foam formation process. Generally it comprises all of these. Such a pre-formed blend of polyol with additives is commonly known as a pre-polyol.

The isocyanate for use either as the foam precursor or to be added as a further component to the foamable composition to induce foam formation is selected on the basis of the density and strength required in the foam composite as well as on the basis of toxicity. It can, for example, be selected from methylene polymethylene polyphenol isocyanates (PMDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (I PDI), PMDI or MDI being preferred. One particularly suitable example is diphenylmethane-4,4'-diisocyanate. Other suitable isocyanates are commercially available from, for example, Bayer Material Science, BASF or DOW Chemicals.

In order to form a foam composite, a blowing agent is required. The blowing agent can be a chemical blowing agent or a physical blowing agent. In some embodiments, the foamable composition comprises a blowing agent. Alternatively, the blowing agent can be added to the foamable composition together with a further component that induces foam formation. In the context of polyurethane foam composites, in a preferred embodiment, the blowing agent is water. Water acts as a chemical blowing agent, reacting with the isocyanate to form CO₂, which acts as the blowing gas.

When the foam-precursor is a polyol, in one embodiment, the foamable composition comprises water as a blowing agent. The water is usually present in such a foamable composition in an amount from 0.3 to 2 % by weight of the foamable composition.

As an alternative, or in addition, a physical blowing agent, such as liquid CO₂ or liquid nitrogen could be included in the foamable composition or added to the foamable composition as part of the further component that induces foam formation.

The foamable composition, in an alternative embodiment, is suitable for forming a phenolic foam. Phenolic foams are formed by a reaction between a phenol and an aldehyde in the presence of an acid or a base. A surfactant and a blowing agent are generally also present to form the foam. Therefore, the foamable composition could comprise, in addition to the man-made vitreous fibres, a phenol and an aldehyde (the foam precursor), a blowing agent and a surfactant. Alternatively, the foamable composition could comprise as the foam precursor, a phenol but no aldehyde, or an aldehyde but no phenol.

Whilst foamable compositions suitable for forming polyurethane or phenolic foams are preferred, it is also possible to use foamable compositions suitable for polyisocyanurate, expanded polystyrene and extruded polystyrene

In an alternative embodiment, the polyurethane foam composite is especially a polyisocyanurate foam composite, where the blowing agent is preferably pentane. Pentane has the advantage over other blowing agents that it is more environmentally friendly and cost effective than for instance HFC blowing agents. Pentane can be c-pentane, i-pentane, or n-pentane or a mixture of two or more of these. The choice between c-pentane, i-pentane and n-pentane is dependent on the production method. They are quite different in boiling point, initial thermal conductivity, aged thermal conductivity and price. The preferred pentane in this invention is n-pentane based on the price and aged thermal conductivity.

The foamable composition that can be used to make the foam composite used in the invention can contain additives in addition to the foam precursor and the man-made vitreous fibres. When it is desired to include additives in the foam composite, as an alternative to including the additives in the foamable composition comprising man-made vitreous fibres, the additive can be included with a further component that is added to the foamable composition to induce foam formation.

As an additive, it is possible for the composition or the foam composite to comprise a fire retardant such as expandable powdered graphite, aluminium trihydrate or magnesium hydroxide. The amount of fire retardant in the composition is preferably from 3 to 20% by weight, more preferably from 5 to 15% by weight and most preferably from 8 to 12 % by weight. The total quantity of fire retardant present in the polymeric foam composite material is preferably from 1 to 10%, more preferably from 2 to 8% and most preferably from 3 to 7 % by weight. Alternatively, or in addition, the foamable composition or foam composite can comprise a flame retardant such as nitrogen- or phosphorus-containing polymers. The fibres used in the polymeric foam composite can be treated with binder, which, as a result, can be included in the composition and the resulting foam composite as an additive if it is chemically compatible with the composition. The fibres used usually contain less than 10% binder based on the weight of the fibres and binder. The binder is usually present in the foamable composition at a level less than 5% based on the total weight of the foamable composition. The foam composite usually contains less than 5% binder, more usually less than 2.5% binder. In a preferred embodiment, the man-made vitreous fibres used are not treated with binder. In some circumstances, it is advantageous, before mixing the man-made vitreous fibres into the foamable composition, to treat the fibres with a surfactant, usually a cationic surfactant. The surfactant could, alternatively, be added to the composition as a separate component. The presence of a surfactant, in particular a cationic surfactant, in the composition and as a result in the polymeric foam composite material has been found to provide easier mixing and, therefore, a more homogeneous distribution of fibres within the foamable composition and the resulting foam.

One advantage of the described polymeric foam composite is that it is possible to incorporate larger percentages of fibres into the foamable composition, and therefore into the resulting foam, than would be the case with longer fibres. This allows higher levels of fire resistance and compressive strength to be achieved. Preferably, the composition comprises at least 15% by weight, more preferably at least 20% by weight, most preferably at least 35% by weight of man-made vitreous fibres. The polymeric foam composite material itself preferably comprises at least 10% by weight, more preferably at least 15% by weight, most preferably at least 20% by weight of man-made vitreous fibres. Usually the foamable composition comprises less than 85% by weight, preferably less than 80%, more preferably less than 75% by weight man-made vitreous fibres. The resulting foam composite usually contains less than 80% by weight, preferably less than 60%, more preferably less than 55% by weight man- made vitreous fibres.

The polymeric foam composite used in the invention comprises a polymeric foam and man-made vitreous fibres. The foam composite can be formed from the foamable composition as described above. It is preferred that the polymeric foam is a polyurethane foam or a phenolic foam. Polyurethane foams are most preferred due to their low curing time.

The first step in the production of the polymeric foam composite material is to form the foamable composition comprising the foam precursor and the mineral fibres. The fibres can be mixed into the foam precursor by a mechanical mixing method such as use of a rotary mixer or simply by stirring. Additives as discussed above can be added to the foamable composition.

Once the fibres and foam precursor have been mixed, the formation of a foam can then be induced. The manner in which the foam is formed depends on the type of foam to be formed and is known to the person skilled in the art for each type of polymeric foam. In this respect, reference is made to "Handbook of Polymeric Foams and Foam Technology" by Klempner et al. For example, in the case of a polyurethane foam, the man-made vitreous fibres can be mixed with a polyol as the foam precursor. The foamable composition usually also comprises water as a chemical blowing agent. Then foaming can be induced by the addition of an isocyanate. In the case where a further component is added to the foamable composition to induce foaming, this can be carried out in a high pressure mixing head as commercially available. In one embodiment, foam formation is induced by the addition of a further component and the further component comprises further man-made vitreous fibres, wherein at least 50% by weight of the further man-made vitreous fibres have a length of less than 100 micrometres. Including man-made vitreous fibres in both the foamable composition and the further component can increase the overall quantity of fibres in the foam composite, by circumventing the practical limitation on the quantity of fibres that can be included in the foamable composition itself. For example in the context of polyurethane foam composites a foamable composition could comprise a polyol, man-made vitreous fibres and water. Then foaming could be induced by the addition, as the further component, of a mixture of isocyanate and further man-made vitreous fibres, wherein at least 50% of the man-made vitreous fibres have a length of less than 100 micrometres.

In essentially the same process, the mixture of isocyanate and man-made vitreous fibres could constitute the foamable composition, and the mixture of polyol, water and man-made vitreous fibres could constitute the further component.

The quantity of man-made vitreous fibres in the further component is preferably at least 10 % by weight, based on the weight of the further component. More preferably the quantity is at least 20% or at least 30% based on the weight of the further component. Usually, the further component comprises less than 80% by weight, preferably less than 60%, more preferably less than 55% by weight man- made vitreous fibres.

The polymeric foam composite is the material that provides compressive strength and resistance to compression to the thermal insulating element. Therefore, preferably the polymeric foam composite has a compressive strength of at least 1500 kPa and a compression modulus of elasticity of at least 60,000 kPa as measured according to European Standard EN 826:1996. The following are examples of the polymeric foam composite materials as used in the invention as compared with other polymeric foam composite materials.

Example 1 (comparative)

100.0 g of a commercially available composition of diphenylmethane-4,4'- diisocyanate and isomers and homologues of higher functionality, and 100.0 g of a commercially available polyol formulation were mixed by propellers for 20 seconds at 3000 rpm. The material was then placed in a mold to foam, which took about 3 min. The following day, the sample was weighed to determine its density and the compression strength and compression modulus of elasticity were measured according to European Standard EN 826:1996.

Compressive strength: 1 100 kPa

Compression modulus of elasticity: 32000 kPa

Example 2

100.0 g of the same commercially available polyol formulation as used in Example 1 was mixed with 200.0 g ground stone wool fibres, over 50% of which have a length less than 64 micrometres, for 10 seconds. Then 100.0 g of the commercially available composition of diphenylmethane-4,4'-diisocyanate was added and the mixture was mixed by propellers for 20 seconds at 3000 rpm.

The material was then placed in a mold to foam, which took about 3 min. The following day, the sample was weighed to determine its density and the compression strength and compression modulus of elasticity were measured according to European Standard EN 826:1996.

Compressive strength: 1750 kPa

Compression modulus of elasticity: 95000 kPa

Example 3 (comparative) 100.0 g of the same commercially available polyol formulation as used in Examples 1 and 2 was mixed for 10 seconds with 50.0 g stone fibres having a different chemical composition from those used in Example 2 and having an average length of 300 micrometres. 100.0 g of the commercially available composition of diphenylmethane-4,4'-diisocyanate was added. The mixture was then mixed by propellers for 20 seconds at 3000 rpm. The material was placed in a mold to foam, which takes about 3 min. The following day, the sample was weighed to determine its density and the compression strength and compression modulus of elasticity were measured according to European Standard EN 826:1996.

Compressive strength: 934 kPa

Compression modulus of elasticity: 45000 kPa Example 4

Example 3 was repeated, but the fibres were ground such that greater than 50% of the fibres had a length less than 64 micrometres. Following this grinding it became possible to mix 200g of the fibres with the polyol mixture.

Compressive strength: 1785 kPa

Compression modulus of elasticity: 1 15000 kPa.

Example 5

Small flame tests were carried out according to ISO/DIS 1 1925-2 to establish the fire resistance of polymeric foam composites as used in the invention compared with the fire resistance of composites comprising quartz sand rather than fibres according to the invention. The foam used was polyurethane foam. The fibres used had a composition within the following ranges.

Al₂0₃ 17 to 23wt%

Ti02 up to 2wt% Fe₂0₃ 2 to 12wt%

CaO 5 to 18wt%

Mg0 4 to 10wt%

Na₂0 up to 15wt%

K₂0 up to 15wt%

P₂0₅ up to 3wt%

MnO up to 3wt%

B₂0₃ up to 3wt% The quartz sand used had a particle size up to 2mm. In each composite tested, expanding graphite was included as a fire retardant. The test involved measuring the height of a flame from each composite under controlled conditions. The results were as follows:

Figure 4 is an environmental scanning electron microscope image of a polyurethane foam composite material as used according to the invention, in which the fibres have a length distribution such that 95% by weight of the fibres have a length below 100 micrometres and 75% by weight of the fibres have a length below 63 micrometres. The composite contains 45% fibres by weight of the composite. The instrument used was ESEM, XL 30 TMP (W), FEI/Philips incl. X-ray microanalysis system EDAX. The sample was analysed in low vacuum and mixed mode (BSE/SE).

Claims

1 . A floor panel for use in a raised floor system, the panel comprising:

a floor surface tile; and

2. A floor panel according to claim 1 , wherein a glass fibre mesh is disposed on a face of the base layer that is opposite to the layer of foam composite material.

3. A floor panel according to claim 1 or claim 2, wherein the base layer and the layer of foam composite material are bonded together without any extrinsic attachment means.

4. A floor panel according to any preceding claim, wherein an upper layer comprising man-made vitreous fibres and binder and having a density of at least 300kg/m³, such as at least 450 kg/m³, such as around 500 kg/m³ is disposed between the layer of polymeric foam composite material and the floor surface tile.

5. A floor panel according to claim 4, wherein the upper layer and the layer of foam composite material are bonded together without any extrinsic attachment means.

6. A floor panel according to any preceding claim, wherein at least 60% by weight of the man-made vitreous fibres present in the polymeric foam composite material have a length less than 65 micrometres.

7. A floor panel according to any preceding claim, wherein at least 80% by weight of the man-made vitreous fibres present in the polymeric foam composite material have a length less than 125 micrometres.

8. A floor panel according to any preceding claim, wherein at least 95% by weight of the man-made vitreous fibres present in the polymeric foam composite material have a length less than 250 micrometres.

9. A floor panel according to any preceding claim, wherein the man-made vitreous fibres present in the foam composite material have an average diameter of from 2 to 6, preferably from 3 to 6 micrometres.

10. A floor panel according to any preceding claim, wherein the man-made vitreous fibres present in the polymeric foam composite material have a content of oxides as follows:

Si0₂ 25 to 50wt%, preferably 38 to 48wt%

Al₂0₃ 12 to 30wt%, preferably 15 to 28wt%, more preferably 17 to 23 wt%

Ti0₂ up to 2wt%

Fe₂0₃ 2 to 12wt%

CaO 5 to 30wt%, preferably 5 to 18wt%

MgO up to 15wt%, preferably 4 to 10wt%

Na₂0 up to 15wt%

K₂0 up to 15wt%

P₂0₅ up to 3wt%

MnO up to 3wt%

B₂0₃ 0 to 3wt%.

1 1 . A floor panel according to any preceding claim, wherein the polymeric foam is a polyurethane foam.

12. A floor panel according to any preceding claim, wherein the polymeric foam composite material comprises at least 10% by weight, preferably at least 15% by weight, more preferably at least 20% by weight of man-made vitreous fibres.

13. A floor panel according to any preceding claim, wherein the polymeric foam composite material comprises less than 80% by weight, preferably less than 60%, more preferably less than 55% by weight of man-made vitreous fibres.

14 A raised floor system comprising a support system extending upwards from a floor and a plurality of floor panels as described in any of claims 1 to 13, supported at their edges by the support system.

15. A raised floor system according to claim 14, wherein the support system comprises a plurality of metallic pillars and preferably wherein the pillars are joined at their upper ends by a grid of metallic bars that support the floor panels along their edges.

16. A method of installing a raised floor comprising:

providing a support system extending upwards from a floor; and positioning a plurality of floor panels according to any of claims 1 to 13 on the support system so that the floor panels are supported at their edges by the support system.

17. A method according to claim 16, wherein the support system comprises a plurality of metallic pillars and preferably a grid of metallic bars at the upper end of the pillars.

18. A computer server room comprising a raised floor system according to claim 14 or claim 15.