The invention relates to a thermal insulating element for the insulation of flat roofs, a roof insulation system and the use of the thermal insulating element on flat roofs.

Insulating elements for flat roofs are required to have a number of different properties. As with all insulating elements for buildings, a high level of thermal insulation is important, as is fire resistance. Furthermore, flat roofs must be insulated in such a way that it is possible for roofers and other construction workers to stand and walk on top of the insulating elements. This means that the flat roof insulation must have high compressive strength as well as high point load resistance. One conventional solution has been to use mineral fibre boards of high density. Such roofing boards have the advantages of high rigidity, high compressive strength and high point load resistance. They are also non-combustible.

In recent years, however, environmental concerns have led to a trend in which building regulations now require an increased thickness of insulation on flat roofs. This results in the insulating elements having an increased weight, which causes great disadvantages in the installation process. This in turn leads to increased labour and equipment costs in the installation process. Therefore, a need exists to minimise the weight of insulation elements, whilst maintaining their fire resistance, insulating properties and still meeting the need for sufficient rigidity, compressive strength and point load resistance to allow construction workers to stand and walk on the roof.

In the context of mineral wool insulating elements, decreasing the average weight of mineral wool both decreases the cost of the insulation and improves the thermal insulation properties. However, this decrease in density also results in a decrease in rigidity and compressive strength, which is unacceptable in insulating elements for use on flat roofs. A number of solutions have been proposed. One approach to minimising the weight of the insulating element is to employ relatively low density mineral wool lamellae with a hard plate on top. The lamellae are strips in which the mineral fibres are oriented with a significant component that is perpendicular to the plane of the roof and the top plate. The top plate is usually a high density mineral fibre board. The orientation of the fibres in the lamellae allows a relatively high resistance to compression to be achieved, together with a relatively low density. The lamellae alone are not sufficiently rigid to permit a person to stand or walk on top of them safely. Therefore, a rigid force distributing top plate is required to ensure that it is possible to walk on the insulation elements.

Often, the lamellar strips are supplied and laid individually, with the rigid top plate being laid subsequently. This system has the obvious disadvantage that installation costs are increased by the need to lay many lamellar strips individually in particular due to a constraint on the width of the lamellar strips, which is a result of the production process. A further disadvantage is that the use of lamellae results in a reduction in thermal insulation as compared with when the mineral fibres are predominantly oriented parallel to the surface being insulated.

A similar solution has been to use prefabricated lamellar boards, as described in EP 0560878 B1 and EP 1709132 B1. The use of these boards decreases the installation time and cost, but the lamellae used are generally of a higher density, meaning that the weight of each board becomes a disadvantage.

The lamellae of these known products are manufactured by fibrising a mineral melt, supplying a binder to the fibres, collecting the fibres as a web, cutting the fibre web in the longitudinal direction to form lamellae, cutting the lamellae into desired lengths, turning the lamellae 90° about their longitudinal axis and bonding the lamellae together to form boards.

A further alternative is the use of dual density roof boards. These are described, for example, in EP 1456444 and EP 1456451. In each case, a continuously produced mineral fibre web is separated depth-wise into upper and lower sub- webs. At least the upper sub-web is subjected to thickness compression, before being re-joined with the lower sub-web. The combined web is then cured. The upper layer of mineral fibre boards made by this process has a density of 100 to 300 kg/m ³ . The density of the lower layer is usually from 50 to 150 kg/m ³ .

These dual density boards, therefore, provide sufficient insulation and are suitable for being walked upon due to the high density top layer. However, in order to have sufficient compressive strength, the density of the lower layer is still relatively high, so the overall weight of the board makes it difficult to install, especially when the board is very thick. Therefore, it would be desirable to reduce the overall density and weight of the roof board.

One attempt to improve the compressive strength of an insulating board without a corresponding increase in the density is described in WO00/70161. The insulating element is designed as a one-piece panel element with at least one insulating part of high heat insulating capacity and at least one load-dissipating fillet, made of mineral wool, which has an increased compressive strength in comparison with the mineral wool material of the insulating part and is permanently bonded to the insulating part forming an integral component part of the panel element. The presence of the fillet allows the density of the insulating part to be reduced, whilst still maintaining a reasonable level of compressive strength. It would, however, be desirable to further increase the compressive strength and resistance to compression of insulating elements for flat roofs. EP 450731 discloses a panel-type insulation element, in particular for roofs or outside walls, comprising at least one layer of panel material such as chipboard or plywood and wool material. In one embodiment, a layer of wool material is provided, on either side of which there is a layer of foam material as the panel material. The layer of wool material can be provided with cut-outs running in the thickness direction in each of which there is a plug of foam material joining the layers of foam material on either side of the layer of wool material. The resulting product is said to be light, and have good thermal insulation. The presence of a standard foam material such as polyurethane, however, increases the combustibility of the product. Furthermore, it would be desirable to further increase the resistance to compression of the insulating element.

Therefore, it is an object of the invention to provide an insulating element for roof insulation that is relatively light and has a relatively low density. A further object is to provide an insulating element that has good thermal and acoustic insulation properties. It is also an object of the invention to provide an insulating element having a high level of fire resistance. Finally it is a further object of the invention to provide an insulating element that has a high compressive strength and resistance to compression and has an upper surface suitable for being walked upon.

By "resistance to compression", it is meant that a high level of pressure is required to compress a product by a given amount. For a given material, this is related to the "compression modulus of elasticity", which can be measured according to European standard EN 826:1996.

In a first aspect, the invention provides a thermal insulating element comprising an insulating layer having a first face and a second face, said insulating layer comprising a coherent man-made vitreous fibre-containing insulating material and at least one reinforcing element extending substantially from the first face to the second face of the insulating layer, wherein the reinforcing element comprises a polymeric foam composite material, the composite material 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 less than 100 micrometers.

One main advantage of the thermal insulating element of the invention is its low overall weight and density. In one embodiment, the average density of the complete element is 30 to 100 kg/m ³ , preferably 40 to 80 kg/m ³ , most preferably 50 to 70 kg/m ³ . The low density of the thermal insulating element means that thicker insulating elements can be more easily handled. Preferably the thickness of the insulation element is at least 50 mm, more preferably at least 100 mm, and most preferably at least 120 mm.

In a further aspect, the invention provides a roof insulation system, preferably a flat roof insulation system, comprising:

a roof support,

at least one thermal insulating element according to the invention arranged on top of the roof support, and

a cover layer on top of the thermal insulating element.

In a further aspect, the invention provides the use of the thermal insulating element in a flat roof insulating system.

The thermal insulating element according to the invention comprises an insulating layer and a polymeric foam composite material as described below.

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 1177971.6. The disclosure of that application 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 micrometers and at least 75% of the fibres by weight have a length less than 65 micrometers.

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, for example at least 0.5% or at least 1 % by weight, have a length less than 10 micrometers. 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: Si0 ₂ 25 to 50%, preferably 38 to 48%

Al ₂ 0 ₃ 12 to 30%, preferably 15 to 28%

ΤΊ02 up to 2%

Fe ₂ 0 ₃ 2 to 12%

CaO 5 to 30%, preferably 5 to 18%

MgO up to 15%, preferably 1 to 8% or 4 to 10%

Na ₂ 0 up to 15%

K ₂ 0 up to 15%

P ₂ 0 ₅ up to 3%

MnO up to 3%

These values are all quoted as weight % oxides, with iron expressed as Fe ₂ 0 ₃ , as is conventional. An advantage of using fibres of this composition, 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 AI2O3 is particularly high such as 15 to 28% or 18 to 28%.

Composites including stone fibres of the above composition have also been found to have improved fire resistance as compared with composites in which the filler used does not contain a significant level of iron.

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

Si0 ₂ 37 to 42%

CaO + MgO 34 to 39%

Fe ₂ 0 ₃ up to 1 %

Na ₂ 0 + K ₂ 0 up to 3%

These values are all quoted as weight % oxides, with iron expressed as Fe ₂ 0 ₃ , as is conventional. 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 produced 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, the present inventors have surprisingly 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 the standard production method. 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 from 2 to 6 or from 3 to 6 micrometers. In one preferred embodiment, the fibres have an average diameter of from 3 to 4 micrometres. In another preferred embodiment, the fibres have an average diameter of from 5 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 often comprise water, which can act as a chemical blowing agent in the foam formation process. 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 diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), 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 CO ₂ , 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 CO ₂ 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 forming polyisocyanurate, expanded polystyrene and extruded polystyrene foams.

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 micrometers.

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 micrometers, 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 micrometers. 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 micrometers. Following this grinding it became possible to mix 200g of the fibres with the polyol mixture. Compressive strength: 1785 kPa

Compression modulus of elasticity: 115000 kPa.

Example 5 Small flame tests were carried out to establish the fire resistance of polyurethane composites used in the invention as compared with the fire resistance of composites comprising sand rather than fibres according to the invention. The fibres used had a composition within the following ranges.

Si0 ₂ 38 to 48%

AI ₂ 0 ₃ 15 to 28%

ΤΊ02 up to 2%

Fe ₂ 0 ₃ 2 to 12%

CaO 5 to 18%

MgO 1 to 8%

Na ₂ O up to 15%

K ₂ 0 up to 15%

P ₂ 0 ₅ up to 3%

MnO up to 3%

B ₂ 0 ₃ 0 to 3%

The 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: Fibre Content Sand Content Graphite Content Flame height (cm)

(wt%) (wt%) (wt%)

25 0 8 12-17

25 0 10 7

31 0 10 5

0 25 8 22

0 25 10 1 1

0 31 10 12

The Insulating Layer

The insulating layer of the thermal insulating element of the invention comprises a coherent man-made vitreous fibre-containing insulating material and at least one reinforcing element extending substantially from the first face to the second face of the insulating layer.

The term "coherent" means that the man-made vitreous fibre-containing insulating material is not in the form of a granulate or any other loose insulating material. The coherent man-made vitreous fibre-containing insulating material is preferably mineral wool. The man-made vitreous fibres in the coherent man- made vitreous fibre-containing insulating material can be glass fibres, ceramic fibres, slag wool fibres or any other type of man-made vitreous fibre, but they are preferably stone fibres. Stone fibres have a content by weight of oxides as follows:

Si0 ₂ 25 to 50%, preferably 38 to 48%

Al ₂ 0 ₃ 12 to 30%, preferably 15 to 28%

Ti0 ₂ up to 2%

Fe ₂ 0 ₃ 2 to 12%

CaO 5 to 30%, preferably 5 to 18%

MgO up to 15% preferably 1 to 8% Na ₂ 0 up to 15%

K ₂ 0 up to 15%

P ₂ 0 ₅ up to 3%

MnO up to 3%

B ₂ 0 ₃ 0 to 3%.

These values are all quoted as oxides, as is conventional.

The man-made vitreous fibres present in the coherent man-made vitreous fibre- containing insulating material can be produced by standard methods such as with a cascade spinner or a spinning cup. Usually, the fibres are treated with a binder and collected as a web, before being cured.

In order to provide a thermal insulating element having as low weight and overall density as possible, it is preferred that the coherent man-made vitreous fibre- containing insulating material has a density less than 60 kg/m ³ , more preferably less than 50 kg/m ³ . Since the coherent man-made vitreous fibre-containing insulating material contributes only a very minor portion, if any, of the compressive strength of the insulating layer, it is possible for this material to have such low density. Usually, the density of the coherent man-made vitreous fibre-containing insulating material is at least 20 kg/m ³ , more usually at least 30 kg/m ³ .

The main purpose of the coherent man-made vitreous fibre-containing insulating material is to provide a high level of thermal insulation. Therefore, it is preferred that the coherent man-made vitreous fibre-containing insulating material has a thermal conductivity of less than 40 mW/m-K, more preferably less than 35 mW/m-K and most preferably less than 33 mW/m-K.

In order to provide a good level of insulation, the insulating layer should have a reasonable thickness. In one embodiment, the thickness of the insulating layer is from 80mm to 350mm, preferably from 100 to 300mm, more preferably from 120 to 250mm. The density of the insulating layer should be kept to a minimum, whilst maintaining sufficient compressive strength and resistance to compression. Preferably the density of the insulating layer is from 25 to 60 kg/m ³ , more preferably from 35 to 50 kg/m ³ .

The Reinforcing Element

The thermal insulating element of the invention comprises an insulating layer, which includes a reinforcing element made of a polymeric foam composite material as described above. In the thermal insulating element of the invention, at least one reinforcing element extends substantially from the first face to the second face of the insulating layer. The purpose of the reinforcing element is to increase the compressive strength and resistance to compression of the insulating elements. When a plate is disposed at one face of the insulating layer (either a top plate that is part of the thermal insulating element or a separate plate that is laid on top of the insulating layer during installation), this allows the insulating element to have sufficient strength to allow a construction worker to stand and walk on the insulating element safely. The reinforcing element or elements can take any shape or form, which allow them to confer compressive strength and resistance to compression to the thermal insulating element. Typically, in order to achieve this goal, it is necessary for the reinforcing element to extend substantially from the first face of the insulating layer to the second face of the insulating layer, because the coherent man-made vitreous fibre-containing insulating material generally has a very low compressive strength and resistance to compression. In one embodiment the reinforcing elements are shaped as columns. The columns can have any suitable cross-sectional shape. In one embodiment, the columns are cylindrical. However the shape of the columns can also be somewhat irregular.

The number of columns in a thermal insulating element depends on a number of factors, including the size of the insulating element, the diameter of the columns and their separation from one another. Generally, however, the thermal insulating element comprises at least 3 columns, preferably at least 4 columns. Often the thermal insulation element has as many as between 25 and 400 columns per m ² , more often between 40 and 200 columns per m ² , such as around 100 columns per m ² . In order to provide maximum stability and compressive strength, it is preferred that the columns are close to perpendicular to the first and second faces of the insulating layer. Preferably, the columns are less than 20 degrees, more preferably less than 10 degrees and more preferably less than 5 degrees from being perpendicular to the first and second faces of the insulating layer. Most preferably the columns are substantially perpendicular to the first and second faces of the insulating layer.

In order to provide sufficient strength, the columns are preferably at least 10 mm in diameter at their narrowest point, more preferably at least 15 or 20 mm in diameter at their narrowest point. Usually, it is not necessary for the columns to be wider than 50 or 40 mm at their narrowest point.

The columns extend substantially from the first face to the second face of the insulating layer, so their length usually corresponds substantially with the thickness of the insulating layer.

It is not desirable for the columns to be positioned too far apart from each other, which would result in large bending stresses being exerted on the top plate, when walked upon, whilst positioning the columns too close too each other would to some extent increase the cost and the weight of the insulating element. Therefore, in a preferred embodiment, columns are positioned from 5 to 20 cm from their nearest neighbour or neighbours. More preferably, columns are positioned from 7 to 15 cm from their nearest neighbour or neighbours. Generally the columns are positioned in rows.

In an alternative embodiment, the reinforcing elements are plate-shaped. The plates can be completely flat, curved or somewhat jagged. It is not necessary for the surfaces of the plates to be perfectly flat. It is even acceptable for the plates to have some holes in them. In order to provide sufficient strength, the plate-shaped reinforcing elements preferably have a thickness at their thickest point of at least 3 mm, more preferably at least 4 mm. In order to avoid excess weight and cost, the thickness is not usually greater than 30 mm at the thickest point, more usually less than 20 mm at the thickest point.

Generally, in order to provide maximum compressive strength and stability, the plates are oriented close to perpendicular to the first and second faces of the insulating layer. Preferably, the plates are less than 20 degrees, more preferably less than 10 degrees and more preferably less than 5 degrees from being perpendicular to the first and second faces of the insulating layer. Most preferably the plates are substantially perpendicular to the first and second faces of the insulating layer.

It is also preferred that the plate-shaped reinforcing elements run through the plane of the insulating layer parallel to one another. In an alternative embodiment, however, at least one plate-shaped reinforcing element runs through the plane of the insulating layer in a direction that is perpendicular to that in which at least one other reinforcing element runs through the plane of the insulating layer. This embodiment provides increased stability to the thermal insulating element.

When the insulating layer includes plates running substantially parallel to each other through the plane of the insulating layer, the distance between those plates is substantially the same at all points. Preferably the distance between those plates is from 7 cm to 25 cm, more preferably from 10 cm to 20 cm.

Top Plate

In order to allow construction workers to walk on the insulating element of the invention, it is necessary, eventually, to provide the insulating element with a top plate. In some embodiments, however, the insulating layer can be provided without a top plate and a separate top plate can be provided at the point of installation. Therefore, a top plate is not an essential feature of the invention. In one embodiment, however, the thermal insulating element comprises a top plate. The top plate is disposed on at least one face of the insulating layer. This can be the first face or the second face or, in a particular embodiment, both the first face and the second face. In a preferred embodiment, the top plate comprises man-made vitreous fibres and binder and has a density of at least 100 kg/m ³ . The man-made vitreous fibres in the top plate can be any suitable fibres such as glass fibres, ceramic fibres or slag fibres, but are preferably stone fibres. In a more preferred embodiment, the top plate has a density of at least 150 kg/m ³ or at least 180 kg/m ³ , such as around 200 kg/m ³ . The density of the top plate may also be substantially higher, such as around 600 kg/m ³ , or even higher, depending on the circumstances. Typically a top plate of this type is sufficiently rigid and has sufficient point load resistance to allow a construction worker to walk or stand on the thermal insulating element even at points in between the reinforcing elements.

Preferably, the top plate has a bending strength of at least 7 N/m ² and a point load resistance of at least 500 kN. It is possible to use polymeric foam as the top plate material, but a high density mineral fibre board is preferred due to its good bending strength and fire resistance properties. In a particular embodiment, the top plate is produced according to the method set out in International Application PCT/EP2011/069777, which have a particularly high level of strength.

In order to have good strength, preferably, the top plate 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 density and weight of the thermal insulating element to a minimum it is preferred that the top plate has a thickness of less than 40 mm, more preferably less than 30 mm.

The overall density of the thermal insulating element, when it includes a top plate is generally in the range 50-80 kg/m ³ . The top plate can be affixed to the insulating layer, for example by use of an adhesive, or it can be a separate top plate that is arranged on top of the insulating layer as indicated above. In a particularly advantageous embodiment, the top plate or top plates and the reinforcing element can be bonded together without any extrinsic attachment means such as an adhesive. This can be achieved by forming the polymeric foam material in situ and contacting the top plate with the foam composite material as it hardens. This technique has been found to produce a particularly strong connection between the top plate and the reinforcing element, particularly when the top plate comprises man-made vitreous fibres and binder and has a density of at least 100kg/m ³ , such as at least 150 kg/m ³ , such as around 200 kg/m ³ . Roof Insulation Systems

The present invention also relates to roof insulation systems, in particular flat roof insulation systems. As used herein, the term "flat roof means a roof that is substantially horizontal, even though it might be sloping at an angle of up to 5 or 10 degrees to the horizontal.

The insulation systems of the invention comprise a roof support, at least one thermal insulating element according to the invention arranged on top of the roof support, and a cover layer arranged on top of the thermal insulating element.

Generally, in the context of flat roofs, the roof support comprises at least one corrugated steel plate or is a concrete deck. The remaining layers of the roof insulation system can differ depending on whether the roof support is a corrugated steel plate or a concrete deck.

When the roof support comprises at least one corrugated steel plate, it is preferred that a water vapour barrier is arranged between the corrugated steel plate and the thermal insulating elements. Often, the water vapour barrier is a polymer membrane. The water vapour barrier ensures that moisture from humid air beneath the roof does not enter into the roof insulation through openings in the corrugated steel plates or through joints between the steel plates.

For fire safety reasons it is sometimes preferred that a man-made vitreous fibre board is arranged between the corrugated steel plate and the water vapour barrier layer. Preferably the man-made vitreous fibre board has a density of at least 100 kg/m ³ . Preferably the man-made vitreous fibre board has a thickness of between 30 mm and 70 mm, more preferably between 40 mm and 60 mm. The thermal insulating element can be any thermal insulating element according to the invention as described above, but in order to ensure that it is possible to walk on the flat roof once it has been constructed, it is preferred that the thermal insulating element comprises a top plate that is disposed on at least one face of the insulating layer. In an alternative embodiment, however, the thermal insulating element does not comprise a top plate, but a separate plate is laid on top of the thermal insulating element at the point of installation. The separate plate preferably comprises man-made vitreous fibres and binder and has a density of at least 100 kg/m ³ . When the roof support is a corrugated steel plate, the positioning and orientation of the thermal insulating element can be important. It is preferred, especially when there is no man-made vitreous fibre board positioned between the thermal insulating element and the roof support, that the thermal insulating element is positioned such that at least 1 , and preferably more, of the reinforcing elements are positioned over the peaks of the corrugated steel plates, so that there is sufficient support for the insulating element to allow roofers to walk on top of it.

When the reinforcing elements are plate-shaped, it is preferred that the plate- shaped reinforcing elements do not run parallel with the peaks and troughs in the corrugated steel plate. It is especially preferred that the plate-shaped reinforcing elements run at an angle of at least 45 degrees or more preferably substantially perpendicular to the peaks and troughs in the steel plates. When the roof support is a concrete deck, the system can be somewhat simpler. In particular, there is no need for a fire safe man-made vitreous fibre board below the vapour barrier, since the concrete deck provides sufficient fire protection itself.

The roof insulation system of the invention comprises a cover layer on top of the thermal insulating elements. The cover layer is the uppermost layer of the roof system and provides weather protection for the roof. Preferably, the cover layer comprises a bituminous sub-layer and a top layer. The top layer is preferably a bituminous top layer or a polymeric film. In embodiments where the top layer is a polymeric film, it is preferably a PVC film.

In the roof insulation systems of the invention, the thermal insulating element is preferably secured to the roof support by mechanical fastening means as is well known in the art of flat roof construction.

Description of Drawings

Figure 1 shows a thermal insulating element 10 according to the invention in which the reinforcing elements are columns 11. The columns 11 extend from the first face 12 to the second face 13 of the insulating layer and a top plate 14 is disposed on the first face 12 of the insulating layer. The columns 1 1 are substantially perpendicular to the first face 12 and the second face 13 of the insulating layer. Coherent man-made vitreous fibre-containing insulating material forms the majority of the insulating layer in terms of volume. In the shown embodiment the columns 11 are arranged in a square pattern. The distance between the columns 11 is 100 mm, such that there are 100 columns per m ² . Figure 2 shows another embodiment of the thermal insulating element 110 of the invention, in which the reinforcing elements 1 1 1 are plate-shaped. The reinforcing elements 1 1 1 extend substantially from the first face 1 12 to the second face 1 13 of the insulating layer. They run through the plane of the insulating layer substantially parallel to each other. The plate-shaped reinforcing elements 1 11 are also substantially perpendicular to the first face 1 12 and the second face 1 13 of the insulating layer. A top plate 1 14 is disposed on the first face 1 12. Again, coherent man-made vitreous fibre-containing insulating material forms the majority of the insulating layer in terms of volume. In the shown embodiment the distance between the plate-shaped reinforcing elements 1 11 is 150 mm.

In preferred embodiments the insulating element 10,1 10 comprises 4 to 20% by weight, preferably 6 to 15% by weight, more preferably 8 to 12% by weight, of the polymeric foam composite material which forms the reinforcing elements 1 1 ,1 1 1.

Figure 3 shows a roof insulation system according to the invention. The system comprises a roof support in the form of at least one corrugated steel plate 20. A thermal insulating element 10 provided with a top plate 14 is arranged on top of the corrugated steel plate 20. The thermal insulating element is of the type shown in Figure 1 , i.e. the insulating layer comprises man-made vitreous fibre- containing insulating material provided with columns 1 1 of a polymeric foam composite material.

A vapour barrier 21 is arranged between the corrugated steel plate 20 and the thermal insulating element 10, and a cover layer 22 is arranged on top of the top plate 14. In some embodiments for a roof insulation system according to the invention a fire protection board (not shown) can be arranged between the corrugated steel plate 20 and the vapour barrier 21. The fire protection board may be made of man-made vitreous fibres. In other embodiments the roof support is a concrete deck instead of a corrugated steel plate. However, generally the roof insulation system above the roof support is similar to what is shown in Figure 3. Figure 4 is an environmental scanning electron microscope image of a polyurethane foam composite 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 micrometers and 75% by weight of the fibres have a length below 63 micrometers. 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). The image shows the cellular structure of the foam and demonstrates that the man-made vitreous fibres generally sit in the walls of the cells of the foam without penetrating into the cells themselves to a significant extent.