WO2012062796A1

WO2012062796A1 - Method for manufacturing an aerogel-containing composite and composite produced by said method

Info

Publication number: WO2012062796A1
Application number: PCT/EP2011/069727
Authority: WO
Inventors: Daan Louis De Kubber; Dorthe Lybye
Original assignee: Rockwool International A/S
Priority date: 2010-11-09
Filing date: 2011-11-09
Publication date: 2012-05-18

Abstract

The invention relates to a method for manufacturing an aerogel-containing composite and the novel aerogel-containing composite produced by that method.

Description

METHOD FOR MANUFACTURING AN AEROGEL-CONTAINING COMPOSITE AND COMPOSITE PRODUCED BY SAID METHOD

It has previously been attempted to provide an aerogel-containing composite for use as an insulating material. For example WO 97/10187 A1 relates to a composite aerogel material and a method for manufacturing an aerogel containing composite comprising the steps of providing fibres in an amount of from 0.1 to 40%-vol, providing an aerogel particulate material having an average particle diameter smaller than 0.5 mm in an amount of from 5 to 97%-vol, providing a resin binder, mixing the ingredients, and consolidating the

ingredients by subjecting the material to hot pressing.

PCT/EP10/61 149 proposes a method of making an aerogel-containing composite. The boards made with this process provide adequate strength for most purposes.

Boards made of aerogel and stone wool are used as indoor insulation; these boards are provided with a glassfibre fleece on both sides of the aerogel-stone wool composite to provide mechanical strength to the board when handling the board.

One of the main problems of previous aerogel containing composites and methods for manufacturing thereof is lack of cohesion and mechanical strength of the composites.

It is therefore an object of the present invention to provide an aerogel-containing

composite having high mechanical strength and a method for manufacturing the composite.

According to the invention this object is achieved with a method for manufacturing an aerogel-containing composite, said method comprising the steps of:

providing mineral fibres in an amount of from 3 to 80 wt % of the total weight of starting materials, providing an aerogel particulate material in an amount of from 10 to 75 wt % of the total weight of starting materials, providing a binder in an amount of from 1 to 30 wt % of the total weight of starting materials, wherein the binder is a polyisocyanurate-forming binder, suspending the fibres in a primary air flow and suspending the aerogel particulate material in the primary air flow, thereby mixing the suspended aerogel particulate material with the suspended fibres, mixing the binder with the mineral fibres and/or aerogel particulate material before, during or after mixing of the fibres with the aerogel particulate material, collecting the mixture of mineral fibres, aerogel particulate material and binder and pressing and curing the mixture to provide a consolidated composite with a density of from 100 kg/m³ to 800 kg/m³, such as 120 kg/m³ to 400 kg/m³.

This method can be used to produce a novel aerogel-containing composite.

The percentages mentioned herein are based on dry weight of starting materials.

With the method according to the invention as defined above a very versatile and cost efficient method for manufacturing an aerogel containing composite is achieved. A wide range of properties in terms of e.g. mechanical strength, thermal insulation capability etc can be produced by altering the quantity of each component. This means that with the same method a variety of different composites can be made that are tailor-made for specific purposes.

The provision of an isocyanurate-based binder has resulted in a much stronger board with enhanced bending strength as compared to a board made under the same conditions but with another binder system. Qualitatively, it was found that a board made with a phenol formaldehyde dry binder was difficult to handle without breaking whereas a board made with an isocyanurate-based binder could be handled without breaking.

Thus, the board made with an isocyanurate-based binder did not need a glassfibre fleece layer applied on its major surfaces to enhance the strength and is therefore are less costly product and made in a simpler process. It has also been found that the composites of the present invention as a result of their homogeneity can be machinable in a similar way to wood. By "machinable" it should be understood that the composite can be machined in ordinary wood forming machinery, such as saws and shaping machines, e.g. grooving machines, surface milling cutters etc.

The products produced by the method of the invention have a variety of uses,

predominantly as building elements. In particular, the products can be in the form of panels. In general, the products are used in applications where mechanical stability and an even surface finish as well as insulating properties are important. In some applications, the panels can be used as acoustically absorbing ceiling or wall panels. In other applications, the panels can be used as insulating outer cladding for buildings.

Preferably, the composite is in the form of a panel. Preferably the thickness of the panel is from 4 to 50 mm. In some embodiments, especially where the panel is used as cladding on a building, the thickness of the panel is preferably from 4 to 12 mm. In alternative embodiments, especially where the panel is used as an insulation panel for a wall of a ceiling, the thickness of the panel is preferably from 12 to 50 mm, more preferably from 15 to 30 mm and most preferably from 18 to 25 mm.

"Aerogel" when used in the broader sense means a gel with air as the dispersion medium. Within that broad description, however, exist three types of aerogel, which are classified according to the conditions under which they have been dried.

These materials are known to have excellent insulating properties owing to their very high surface areas, and high porosity. They are manufactured by gelling a flowable sol-gel solution and then removing the liquid from the gel in a manner that does not destroy the pores of the gel.

Where a wet gel is dried at above the critical point of the liquid, there is no capillary pressure and therefore relatively little shrinkage as the liquid is removed. The product of such a process is very highly porous and is known as an aerogel, the term being used in the narrow sense. On the other hand, if the gel is dried by evaporation under sub-critical conditions, the resulting product is a xerogel. In the production of a xerogel, the material usually retains a very high porosity and a large surface area in combination with a very small pore size. In the wider sense of the word, aerogels also encompass dried gel products, which have been dried in a freeze-drying process. These products are generally called cryogels.

The term "aerogel" in its broader sense of "gel having air as the dispersion medium" encompasses each of aerogels in the narrower sense, xerogels and cryogels. As used herein, the term "aerogel" denotes aerogels in the broader sense of a gel having air as the dispersion medium.

Preferably, the aerogel used in the present invention has been dried under supercritical conditions i.e. an aerogel "in the narrow sense" as described above.

The aerogel used in the present invention is in particulate form. In a preferred embodiment, the particles of aerogel will have an average diameter of from 0.2 to 5 mm. More

preferably, the average diameter of the particies in the aerogel particulate material will be from 0.3 to 4 mm. and most preferably the average diameter of particles in the aerogel particulate material will be from 0.7 to 1 .2 mm. These particle sizes are measured as weight averages and refer to the particle size of the starting material, rather than that present in the final composite.

During the method of the invention, in some embodiments, the average particle size of the aerogel can be reduced, as a result of the method steps used.

The aerogel particulate material can be any type of aerogel. In particular, the aerogel can be organic or inorganic. In view of their fire-resistant properties, inorganic aerogels are usually preferred. Organic aerogels include carbon aerogels and polymeric aerogels.

Organic aerogels generally have a lower price and better insulation properties. Preferred inorganic aerogels are based on metal oxides. Particularly preferred materials are silica, carbides and alumina. Silica aerogels, such as "Nanogel® Fine Particie Aerogel" from Cabot International are most preferred. The aerogel particulate materials have a low density, typically from 0.01 g/cm3 to 0.3 g/cm3 The thermal conductivity of the aerogel particulate material is preferably from 5 to 20 mW/mK, more preferably from 7 to 16 mW/mK and most preferably from 9 to 12 mW/mK.

The precise quantity of mineral fibres used in the method and present in the composite of the invention is chosen so as to maintain appropriate strength and appropriate thermal insulation value, depending on the appropriate application, as a high quantity of fibres increases the strength of the composite, but decreases the thermal insulation value. This means that the lower limit of 3 wt % results in a composite having unusually good thermal insulation properties, and only adequate strength, which may be advantageous for some composites, where the strength is less important. If strength of the composite is particularly important the amount of fibres can be increased to the upper limit of 80 wt %, but this will result in only adequate thermal insulation properties. For a majority of applications a suitable composition will include a fibre amount of from 20 to 70 wt % or from 25 to 70 wt %. Most usually, a suitable quantity of fibres will be from 30 to 60 wt %.

Similarly the amount of aerogel particulate material used is chosen in order to provide both appropriate strength and thermal insulation value, as a high amount of aerogel particulate material decreases the strength of the composite, but increases the thermal insulation value. This means that the lower limit of 10 wt % aerogel particulate material results in a composite having excellent strength, but mediocre thermal insulation properties, which may be advantageous for some composites, where the strength is very important. If thermal insulation value of the composite is important the amount of aerogel particulate material can be increased to the upper limit of 75 wt %, but this will result in mediocre strength. For a majority of applications a suitable composition will include an aerogel particulate material amount of from 30 to 60 wt %, from 35 to 55 wt % or most typically from 40 to 50 wt %.

The amount of binder is also chosen on the basis of desired strength and cost, plus properties such as reaction to fire and thermal insulation value. The lower limit of 1 wt % results in a composite with a lower strength, which is however adequate for some applications, and has the benefit of relatively low cost and potential for good thermal insulation properties. In applications where a high mechanical strength is needed, a higher amount of binder should be used, such as up to the high limit of 30 wt %, but this will increase the cost of the resulting product and further the reaction to fire will often be less favourable.

Furthermore, the insulation properties of the aerogel particles will not be compromised by the binder, which would be the case if binder connected to the surface of the aerogel particles. This would be expected with a polyisocyanurate-based binder because this comprises a hydrophobic component dispersed in water, however the insulation properties are hardly not affected.

The mineral fibres (also known as man-made vitreous fibres or MMVF) used according to the present invention could be any mineral fibres, including glass fibres, ceramic fibres or stone fibres, but preferably, stone fibres are used. Stone wool fibres generally have a content of iron oxide at least 3% and alkaline earth metals (calcium oxide and magnesium oxide) from 10 to 40%, along with the other usual oxide constituents of mineral wool.

These are silica; alumina; alkali metals (sodium oxide and potassium oxide) which are usually present in low amounts; and can also include titania and other minor oxides.

Fibre diameter is often in the range 3 to 20 microns, in particular 5 to 10 microns, as conventional.

In one embodiment, the mineral fibres include glass fibres preferably in an amount up to 20%, more preferably up to 15% and most preferably up to 10% of the total weight of starting materials. The remaining mineral fibres are preferably stone fibres. The glass fibres preferably have a length of from 10mm to 50mm, more preferably from 15mm to 40mm and most preferably from 20mm to 30mm. These glass fibres serve to reinforce the composite.

Preferably, the mineral fibres, and aerogel particulate material together form at least 60%, more preferably at least 65% and most preferably at least 70% of the total weight of starting materials. Preferably, the mineral fibres, binder and aerogel particulate material make up at least 80%, more preferably at least 90% and most preferably substantially all of the total weight of starting materials.

In one embodiment, the fibres are provided in the form of a collected web and the method further comprises subjecting the collected web of fibres to a disentanglement process. The disentangled fibres are subsequently suspended in the primary air flow.

As used herein, the term "collected web" is intended to include any mineral fibres that have been collected together on a surface, i.e. they are no longer entrained in air, e.g. granulate, tufts or recycled web waste.

The collected web could be a primary web that has been formed by collection of fibres on a conveyor belt and provided as a starting material without having been cross-lapped or otherwise consolidated. Alternatively, the collected web could be a secondary web that has been formed by cross-lapping or otherwise consolidating a primary web. Preferably, the collected web is a primary web.

A feeding mechanism may be provided for feeding in a web. The feeding mechanism may comprise a set of driven feed rollers. For example the web may be gripped between the feed rollers to be driven by the feed rollers for controlled advancing of the web to the disentanglement process.

In one embodiment, the disentanglement process comprises feeding the web of mineral fibres from a duct with a lower relative air flow to a duct with a higher relative air flow. In this embodiment, the disentanglement is believed to occur, because the fibres that enter the duct with the higher relative air flow first are dragged away from the subsequent fibres in the web. This type of disentanglement is particularly effective for producing open tufts of fibres, which can be penetrated by the aerogel particulate material.

Preferably, the speed of the higher relative air flow is from 20 m/s to 150 m/s or from 30 m/s to 120 m/s. More preferably it is from 40 m/s to 80 m/s and most preferably from 50 m/s to 70 m/s. The higher relative air flow can be separate from the primary air flow, but more usually, it will feed into the primary air-flow.

Preferably, the difference in speed between the lower relative air flow and the higher relative air flow is at least 20 m/s, more preferably at least 40 m/s and most preferably at least 50 m/s.

As used herein, the term "air flow" should be understood broadly so as to include not only a flow of air comprising gases in the proportions present in the atmosphere of Earth, but also a flow of any suitable gas or gases in any suitable proportions.

According to a particularly preferred embodiment, the disentanglement process comprises feeding the collected web to at least one roller which rotates about its longitudinal axis and has spikes protruding from its circumferential surface. In this embodiment, the rotating roller will usually also contribute at least in part to the higher relative air flow. Often, rotation of the roller is the sole source of the higher relative air flow.

In some embodiments there are at least two rollers. These rollers may operate in tandem or sequentially.

The roller may be of any suitable size, but in a preferred embodiment, the roller has a diameter based on the outermost points of the spikes of from 20cm to 80cm or more preferably from 30cm to 70cm. Even more preferably the diameter is from 40cm to 60cm and most preferably from 45cm to 55cm. The roller may rotate at any suitable speed. For most embodiments a suitable rate of rotation for the roller is from 500 rpm to 5000 rpm, preferably from 1000 rpm to 4000 rpm, more preferably from 1500 rpm to 3500 rpm, most preferably from 2000 rpm to 3000 rpm.

The dimensions and rate of rotation of the roller can be selected to provide a given speed at the circumference of the roller. In general, a high speed will result in a more effective disentanglement process, although this will depend on the type of web of mineral fibres used and the exact form of the roller. In most embodiments it will be suitable for the outermost points of the spikes of the roller to move at a speed of from 20 m/s to 150 m/s, preferably from 30 m/s to 120 m/s, more preferably from 40 m/s to 80 m/s and most preferably from 50 m/s to 70 m/s.

The spikes may be permanently fixed to the roller for optimum resistance to wear and tear. For example the spikes may be fixed by gluing or welding the spikes in blind holes arranged in the roller outer periphery. Alternatively the spikes may be replaceable. This can for example be accomplished by the roller being a hollow cylinder with through holes in the cylindrical wall. The spikes can then for example have a head and be inserted through the holes from inside through the holes. Hereby spikes can be replaced if they are broken or worn. Further by having replaceable spikes it is possible to change the pattern of the spikes. Hereby it is possible to optimize the pattern for different types of material to be disentangled, e.g. loose mineral wool fibres, or a collected web of mineral wool fibres impregnated with a liquid binder.

The roller is preferably positioned within a substantially cylindrical chamber. The chamber will have an inlet duct through which the mineral fibres and optionally the aerogel particulate material and binder are fed to the roller. The chamber will also have an outlet through which the disentangled mineral fibres and optionally the aerogel particulate material and binder are expelled. Preferably, they are expelled in the primary air flow through the outlet.

In preferred embodiments, the mineral fibres and optionally the binder and aerogel particulate material are fed to the roller from above. It is also preferred for the disentangled mineral fibres and optionally the binder and aerogel particulate material to be thrown away from the roller laterally from the lower part of its circumference. In the most preferred embodiment, the mineral fibres are carried approximately 180 degrees by the roller before being thrown off.

The roller preferably occupies the majority of the chamber. Preferably the tips of the spikes are less than 10 cm, more preferably less than 7 cm, and most preferably less than 4 cm from the curved wall of the substantially cylindrical chamber. This results in the air flow created by the roller being greater and a more thorough disentanglement of the fibres by the air flow and by the spikes themselves.

Preferably, the mineral fibres are fed to the roller from above. The disentangled fibres are generally thrown off the roller in the primary air flow. In some embodiments, the roller will contribute to the primary air flow. In other embodiments, the roller will be the sole source of the primary air flow.

The aerogel particulate material can be carried to the primary air flow in any suitable manner.

In one embodiment, a disentanglement process is used and the aerogel particulate material is added to the collected mineral fibre web prior to the fibre disentanglement process and is suspended in the primary air flow together with the disentangled fibres. This method of addition of the aerogel particulate material generally promotes the most effective mixing of the components. In this embodiment, the aerogel particulate material can be pre-mixed with the collected mineral fibre web and optionally the binder in any suitable manner.

Alternatively, the aerogel particulate material can be carried to the primary air flow

suspended in a tributary air flow. The tributary air flow is combined with the primary air flow, thereby mixing the aerogel particulate material with the fibres.

In some embodiments, it is not necessary to use a fibre disentanglement process. In one embodiment, the mineral fibres are provided as fibres entrained in air direct from a fibre- forming process. By this it should be understood that the fibres, having been entrained in air in the formation process (e.g. having been thrown from a spinner) are not collected on a surface, but are transported as a suspension in air into the primary air flow.

In this embodiment, the aerogel particulate material may be supplied direct to the primary air flow, or carried to the primary air flow suspended in a tributary air flow. The tributary air flow is combined with the primary air flow, thereby mixing the aerogel particulate material with the fibres.

Where a tributary air flow carries suspended aerogel particulate material to the primary air flow, the speed of the tributary air flow is generally lower than that of the primary air flow. Typically, the tributary air flow has a speed of from 1 to 20 m/s, preferably from 1 to 13 m/s, more preferably from 2 to 9 m/s and most preferably from 3 to 7 m/s.

According to the invention, the fibres and the aerogel particulate material are suspended in a primary air flow. This allows the components to mix intimately. An advantage of mixing as a suspension in an air flow is that unwanted particles or agglomerations can be sifted out. Such particles are e.g. pearls of the fibres and agglomerations are inter alia heavy chunks of wool, which have not been properly opened up to fibres, such as so-called chewing gum. In tests, mixing in an air flow performed surprisingly well, as it was expected that the very different physical and aerodynamic properties of the particles and the fibres would make this type of mixing impossible. It is remarkable that superior mixing takes place in spite of the difference in density and shape of the particles and fibres. The density of the aerogel particles is in the order of 140 kg/m³, whereas for example mineral wool fibres have a density in the order of 2,500 kg/m3 . This might be expected to cause serious problems in the mixing process using an air flow, but surprisingly does not.

The primary air flow is generally not free from turbulence. In preferred embodiments, there is significant turbulence within the primary air flow as this promotes mixing of the aerogel particulate material with the mineral fibres. According to the present invention, the speed of the primary air flow at its source is preferably from 20 m/s to 150 m/s, more preferably from 30 m/s to 120 m/s, even more preferably from 40 m/s to 80 m/s and most preferably from 50 m/s to 70 m/s.

The primary air flow is preferably a generally lateral air flow. In embodiments where the aerogel particulate material is carried to the primary air flow suspended in a tributary air flow, the primary air flow is preferably generally lateral and the tributary air flow is generally upwards. The primary air flow preferably enters a mixing chamber. In the mixing chamber, turbulence within the primary air flow allows more intimate mixing of the components.

In order to effect a thorough mixing of the fibres and particulate material, it is preferred to configure the apparatus such that the average dwell time of the aerogel particulate material and the fibres within the mixing chamber is at least 0.5s, more preferably at least 2s, or even at least 3s.

However, due to the effectiveness of mixing the aerogel particulate material and the fibres suspended in a gas, it is usually not necessary for the average dwell time of the particulate material and the fibres within the mixing chamber to be greater than 10s. More usually, the average dwell time is less than 7s and most usually the average dwell time is less than 5s.

The ambient temperature within the mixing chamber, when used, is usually from 20 °C to 100 °C, more usually from 30 °C to 70 °C. The temperature could be dependent on outside air temperature, i.e. cold in winter and hot in summer. Elevated temperatures of up to 100 °C could be used for providing a pre-curing of the binder in the mixing chamber.

In specific embodiments, the binder is a material that, under certain conditions, dries, hardens or becomes cured. For convenience, these and similar such processes are referred to herein as "curing". Preferably, these "curing" processes are irreversible and result in a cohesive composite material.

The mineral fibres, binder and aerogel particulate material, when suspended in the primary air flow, are, in some embodiments, subjected to a further air flow in a different direction to the primary air flow. This helps to generate further turbulence in the primary air flow, which assists mixing further. Usually the primary air flow is generally lateral and the further air flow is generally upwards. In some embodiments, a plurality of further air flows is provided.

Preferably the further air flow has a speed of from 1 to 20 m/s, more preferably from 1 to 13 m/s, even more preferably from 2 to 9 m/s and most preferably from 3 to 7 m/s. The mixture of mineral fibres, aerogel particulate material and binder is collected from the primary air flow by any suitable means. In one embodiment, the primary air flow is directed into the top of a cyclone chamber, which is open at its lower end and the mixture is collected from the lower end of the cyclone chamber.

In an alternative embodiment, the primary air flow is directed through a foraminous surface, which catches the mixture as the air flow passes through.

In embodiments where there is a disentanglement process before the fibres are

suspended in the primary air flow, the mixture of mineral fibres, aerogel particulate material and binder is preferably subjected to a further fibre disentanglement process after the mixture has been suspended in the primary air flow, but before the mixture is pressed and cured.

The further disentanglement process may have any of the preferred features of the disentanglement process described previously.

In a particularly preferred method, the mixture of mineral fibres, binder and aerogel particulate material is removed from the primary air flow, preferably in a cyclone chamber, and fed to a rotating roller having spikes protruding from its circumferential surface. The roller of the further disentanglement means may have any of the features described above in relation to the roller to which the collected web can be fed initially.

The mixture of mineral fibres, aerogel particulate material and binder is preferably thrown from the further disentanglement process into a forming chamber.

Having undergone the further disentanglement process, the mixture of mineral fibres, aerogel particulate material and binder is collected, pressed and cured. Preferably, the mixture is collected on a foraminous conveyor belt having suction means positioned below it. In a preferred method according to the invention, the mixture of aerogel particulate material, binder and mineral fibres, having been collected, is scalped before being cured and pressed.

The method may be performed as a batch process, however according to an embodiment the method is performed at a mineral wool production line feeding a primary or secondary mineral wool web into the fibre separating process, which provides a particularly cost efficient and versatile method to provide composites having favourable mechanical properties and thermal insulation properties in a wide range of densities.

By the wording "substantially homogeneous" it should be understood that the composite is homogeneous at a millimetre scale, i.e. a microscope image of a given area on a

millimetre scale is (substantially) identical to other samples of the mixture. It further means that after mixing, the materials are distributed substantially evenly within the composite, i.e. that the aerogel particulates are present in substantially the same amount in the whole composite.

Preferably, the millimetre scale area is 1 mm². However, if the composite contains discrete particles in the order of 100 micron and above, "substantially homogeneous" can be defined in relation to the largest discrete ingredient. Hence it should be understood that the composite is visually homogeneous at a scale related to the largest discrete ingredient, e.g. 10 times the size of the largest particulate. For a particle size of say 1 mm (largest dimension) a visual investigation of an area of e.g. 100 mm² is (substantially) identical to other samples of the mixture. It further means that after mixing, the materials are

distributed substantially evenly within the composite, i.e. that the aerogel particulates are present in substantially the same amount in the whole composite with no visual

accumulations.

Any of the preferred features of the final product described in relation to the method apply equally to the composite of the invention where relevant. The invention will be described in the following by way of example and with reference to the drawings in which

Figure 1 is a schematic drawing of an apparatus for fibre separating and mixing raw materials.

Figure 2 is a schematic drawing of a further disentanglement apparatus as described above.

Apparatus suitable for use in the method of the present invention can be seen in Fig. 1. Where a fibre-forming apparatus and collector are configured to carry a mineral fibre web to the inlet duct 1 , a binder supply means is positioned to supply binder to the mineral fibres and an aerogel particulate supply means is positioned to supply aerogel particulate material to the inlet duct, the apparatus shown could also form part of the first novel apparatus of the invention.

The apparatus comprises an inlet duct 1 for starting materials, e.g. aerogel particles, binder and mineral fibres and for specific raw materials the apparatus may comprise a shredder (not shown) at the inlet duct 1 to at least partly cut up bulky material. At the lower edge of the inlet duct, there is a conveyor 2 that carries the raw materials through the inlet duct 1 . At the upper edge of the inlet duct, conveying rollers 3 assist with feeding the starting materials through the inlet duct 1 . At the end of the inlet duct 1 , a first set of mutually spaced elongate elements 4 extend across the end of the inlet duct 1 . These serve to break up larger pieces of the starting materials, for example the mineral fibre web. In some embodiments, the elongate elements 4 are in the form of rotating brushes that draw the starting materials between them as they rotate.

The starting materials that pass through the end of the inlet then fall downwards into a substantially vertical duct 5. In the embodiment shown, a second set of mutually spaced elongate elements 6 extend across the upper end of the duct. The second set of elongate element is usually more closely spaced than the first. In the embodiment shown, the second set of elongate elements rotate so as to allow sufficiently small pieces of the mineral fibre web to pass through, but carry larger pieces away via a starting material recycling duct 7.

The vertical duct 5 generally becomes narrower at its lower end. In the embodiment shown, the lower end of the vertical duct forms the inlet 8 to the substantially cylindrical chamber 9. As shown, the inlet 8 is at an upper part of the substantially cylindrical chamber 9. In use, starting materials pass through the vertical duct 5 and through the inlet 8 into the

cylindrical chamber 9.

The cylindrical chamber 9 houses a roller 10 having spikes 1 1 protruding from its

circumferential surface 12. The roller 10 shown in Figure 1 rotates anticlockwise as shown in the drawing, so that starting materials are carried from the inlet (8) around the left side of the roller 10 as shown and thrown out laterally in a primary air flow into a mixing chamber 14. The cylindrical chamber 9 and the roller 10 together form the

disentanglement means. The disentanglement means cause disentanglement of the fibres, meaning that the fibres, which may be provided as wool entangled as a web or as tufts, will be worked on to provide more open wool or even loose fibres, thereby facilitating subsequent mixing of the fibres with other components.

In the embodiment shown, the primary air flow is created by the rotation of the roller 10 within the cylindrical chamber 9, and in particular by the movement of the spikes 1 1 and starting material through the space between the circumferential surface of the roller and the curved wall 13 of the cylindrical chamber 9.

The mixing chamber 14 shown in Figure 1 comprises a discharge opening 16 and further air flow supply means 15. The further air flow supply means 15 comprise openings through which the further air flow is supplied. Gauzes 17 are disposed across the openings of the further air flow supply means 15. These gauzes allow the further air flow to pass through into the mixing chamber 14, but are intended to prevent the entry of materials into the supply means. The further air flow supply means 15 direct the further air flow upwards into the mixing chamber 14. The further air flow meets the primary air flow containing the disentangled fibres in the mixing chamber. The further air flow has the effect of carrying the mixture of disentangled fibres, binder and aerogel particulate material upwards within the mixing chamber 14. Some more compacted fibres and pearls of mineral material will not be carried upwards in the mixing chamber, but fall to the lower end and through the discharge opening 16.

The desired mixture of disentangled fibres, aerogel particulate material and binder is carried to the upper part of the mixing chamber 14 where a removal duct 18 is positioned to carry the mixture from the mixing chamber 14. A first air recycling duct 19 is adjoined to the removal duct 18 and recycles some of the air from the removal duct 18 back to the further air supply means 15.

The removal duct leads to a cyclone chamber 20. The cyclone chamber 20 has a second air recycling duct 22 leading from its upper end to the further air supply means 15. A filter 21 is adjoined to the second air recycling duct. In use, the filter 21 removes any stray mineral fibres, aerogel particulate material and binder from the second air recycling duct 22. As air is removed from the upper end of the cyclone chamber 20, the mixture of disentangled fibres, aerogel particulate material and binder falls through a cyclone chamber outlet 23 at the lower end of the cyclone chamber 20.

A collector 24 is positioned below the cyclone chamber outlet 23. In the embodiment shown, the collector 24 is in the form of a conveyor, which carries the collected fibres to a pressing and curing apparatus (not shown).

Figure 2 shows an embodiment of the further disentanglement apparatus, which may optionally be used in the method. The further disentanglement apparatus can be positioned in place of collector 24 as shown in Figure 1 . The further disentanglement apparatus shown comprises roller 25, which is the same as roller 10 in structure. The mixture of components is fed to roller 25 from above and thrown out into forming chamber 26. At its lower end, the forming chamber 26 comprises a foraminous conveyor belt 27, below which suction means 28 are positioned. Scalper 29 is positioned to scalp the top of the mixture to provide an even surface. The scalped material can then be recycled. Foraminous conveyor belt 27 carries the mixture to a press (not shown).

Generally, polyisocyanurate-based binders are formed by trimerization of a polyisocyanate in the presence of a trimerization catalyst. Optionally, at least one further reactant selected from polyols , chain extenders, water, and mixtures thereof, is employed. See, for instance, WO 00/29459, WO 04/1 1 1 101 , WO 06/008780, WO 07/42407, WO 07/4241 1 , WO

07/96216, WO 07/144291 , WO 2010/023060, US 4336341 , US 4540781 , US 6509392, US 2002/0045690 A1 , EP 304005 A1 , EP 1004607 A1 , JP 57-131276 A2, JP 58-01 1529 A2, JP 58-034832 A2, JP 58-145431 A2, JP 62-081590 A2, the entire contents of which is incorporated herein by reference.

A currently preferred polyisocyanurate-forming binder composition is a two-component binder composition with the first component comprising an emulsifiable polyisocyanate and the second component being an aqueous mixture containing a catalyst system, surfactants and silane coupling agents.

Preferably, the polyisocyanurate-forming binder composition does not comprise water glass.

In the context of the present invention, the following terms have the following meaning:

1 ) isocyanate index or NCO index or index : the ratio of NCO-groups over isocyanate- reactive hydrogen atoms from polyols having an equivalent weight of 100 to 2500 present in a composition, given as a percentage : fNCOI x l OO (%),

[active hydrogen ]

The NCO-index expresses the percentage of isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen from said polyols used in a formulation. It should be observed that the isocyanate index as used herein is considered from the point of view of the actual polymerisation process preparing the material involving the isocyanate and the polyol. Any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including such isocyanate-derivatives referred to in the art as

prepolymers) are not taken into account in the calculation of the isocyanate index. Only the free isocyanate groups and the free isocyanate-reactive hydrogens (of said polyols) present at the actual polymerisation stage are taken into account.

2) The expression "isocyanate-reactive hydrogen atoms" as used herein for the purpose of calculating the isocyanate index refers to the total of active hydrogen atoms in hydroxyl groups present in the polyol; this means that for the purpose of calculating the isocyanate index at the actual polymerisation process one hydroxyl group is considered to comprise one reactive hydrogen.

3) The expression "polyisocyanurate" as used herein refers to non-cellular products as obtained by reacting the mentioned polyisocyanates and polyols in the presence of trimerization catalysts at a high index.

4) The term "average nominal hydroxyl functionality" is used herein to indicate the number average functionality (number of hydroxyl groups per molecule) of the polyol or polyol composition on the assumption that this is the number average functionality (number of active hydrogen atoms per molecule) of the initiator(s) used in their preparation.

5) The word "average" refers to number average unless indicated otherwise.

6) A trimerization catalyst is a catalyst enhancing the formation of polyisocyanurate groups from polyisocyanates.

In a preferred embodiment, mineral fibre-polyisocyanurate composites may be produced by a process which comprises combining a polyisocyanate, a polyol and a trimerization catalyst, these three ingredients collectively being referred to as 'reactive binder

composition', with the mineral fibres to be bonded to form a reactive composite, and allowing in a next step this reactive composite to react at elevated temperature, wherein the amount of the polyisocyanate and the polyol is such that the index of the reactive binder composition is 150 - 15000, preferably 250 - 10000.

The polyisocyanate may be chosen from aliphatic, cycloaliphatic, araliphatic and, preferably, aromatic polyisocyanates, such as toluene diisocyanate in the form of its 2,4 and 2, 6 -isomers and mixtures thereof, diphenylmethane diisocyanates and variants thereof, and mixtures of diphenylmethane diisocyanates (MDI) and oligomers thereof having an isocyanate functionality greater than 2 known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates).

Mixtures of toluene diisocyanate, diphenylmethane diisocyanates and/or polymethylene polyphenylene polyisocyanates may be used as well. Preferably the polyisocyanate consists of a) 70-100% and more preferably 80-100% by weight of diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4 '-diphenylmethane diisocyanate and/or a variant of said

diphenylmethane diisocyanate which variant has an NCO value of at least 20% by weight (polyisocyanate a), and b) 30-0% and more preferably 20-0% by weight of another polyisocyanate (polyisocyanate b).

Preferably this polyisocyanate a) is selected from 1 ) a diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4 '-diphenylmethane diisocyanate and the following preferred variants of such diphenylmethane diisocyanate: 2) a carbodiimide and/or uretonimine modified variant of polyisocyanate 1 ), the variant having an NCO value of 20% by weight or more; 3) a urethane modified variant of polyisocyanate 1 ), the variant having an NCO value of 20% by weight or more and being the reaction product of an excess of polyisocyanate 1 ) and of a polyol having an average nominal hydroxyl functionality of 2-4 and an average molecular weight of at most 1000; 4) a prepolymer having an NCO value of 20% by weight or more and which is the reaction product of an excess of any of the aforementioned

polyisocyanates 1 -3) and of a polyol having an average nominal functionality of 2-6, an average molecular weight of 2000-12000 and preferably an hydroxyl value of 15 to 60 mg KOH/g, and 5) mixtures of any of the aforementioned polyisocyanates. Polyisocyanates 1 ) and 2) and mixtures thereof are preferred. Polyisocyanate 1 ) comprises at least 40% by weight of 4,4'-MDI . Such polyisocyanates are known in the art and include pure 4,4'-MDI and isomeric mixtures of 4,4 -MDI and up to 60% by weight of 2,4'-MDI and 2,2'-MDI . It is to be noted that the amount of 2,2'- MDI in the isomeric mixtures is rather at an impurity level and in general will not exceed 2% by weight, the remainder being 4,4'-MDI and 2,4'- MDI . Polyisocyanates as these are known in the art and commercially available; for example Suprasec® 1306 ex Huntsman. The carbodiimide and/or uretonimine modified variants of the above polyisocyanate 1 ) are also known in the art and commercially available; e.g. Suprasec® 2020, ex Huntsman. Urethane modified variants of the above polyisocyanate 1 ) are also known in the art, see e.g. The IC! Polyurethanes Book by G. Woods 1990, 2^nd edition, pages 32-35. Aforementioned prepolymers of polyisocyanate 1 ) having an NCO value of 20% by weight or more are also known in the art. Preferably the polyol used for making these prepolymers is selected from polyester polyols and poiyether polyols and especially from polyoxyethylene polyoxypropylene polyols having an average nominal functionality of 2- 4, an average molecular weight of 2500-8000, and preferably an hydroxy! value of 15-60 mg KOH/g and preferably either an oxy ethylene content of 5-25% by weight, which oxyethylene preferably is at the end of the polymer chains, or an oxyethylene content of 50-90% by weight, which oxyethylene preferably is randomly distributed over the polymer chains.

Mixtures of the aforementioned polyisocyanates may be used as well, see e.g. The !CI Polyurethanes Book by G. Woods 1990, 2^nd edition pages 32-35. An example of such a commercially available polyisocyanate is Suprasec 2021 ® ex Huntsman.

The other polyisocyanate b) may be chosen from aliphatic, cycloaliphatic, araliphatic and, preferably, aromatic polyisocyanates, such as toluene diisocyanate in the form of its 2,4 and 2,6-isomers and mixtures thereof and oligomers of diphenylmethane diisocyanate (MDI) having an isocyanate functionality greater than 2. Mixtures of MDI and these oligomers are known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates). Mixtures of toluene diisocyanate and polymethylene polyphenylene polyisocyanates may be used as well. When polyisocyanates are used which have an NCO functionality of more than 2, the amount of such polyisocyanate used is such that the average NCO functionality of the total polyisocyanate used in the present invention is 2.0-2.2 preferably. The polyisocyanates used in the present invention preferably are liquid at 25°C.

The polyols used preferably have an average equivalent weight of 100-2500 and an average nominal hydroxyl functionality of 2-8. Such polyols may be selected from

polyester polyols, polyether polyols, polyester-amide polyols, polycarbonate polyols, polyacetal polyols and mixtures thereof. Preferably polyether polyols are used, like polyoxyethylene polyols, polyoxypropylene polyols, polyoxybutylene polyols and polyether polyols comprising at least two different oxyalkylene groups, like polyoxyethylene polyoxypropylene polyols, and mixtures thereof. Polyols comprising at least two different oxyalkylene groups may be block copolymers or random copolymers or combinations thereof.

The most preferred polyether polyols used have an average nominal hydroxyl functionality of 2-4, an average equivalent weight of 100-2500, an oxyethylene content of at least 50 % by weight and preferably of at least 65 % by weight (on the weight of the polyether polyol). More preferably such polyether polyols have a primary hydroxyl group content of at least 40 % and more preferably of at least 65 % (calculated on the number of primary and secondary hydroxyl groups). They may contain other oxyalkylene groups like oxypropyiene and/or oxybutylene. Mixtures of these most preferred polyols may be used. No other polyols or other isocyanate-reactive compounds (than these most preferred polyether polyols) having an average equivalent weight of 100-2500 are used preferably. Such polyols are known in the art and commercially available; examples are Caradol® 3602 from Shell, Daltocel® F526, F442, F444 and F555 and Jeffox® WL 440, WL 590 and WL 1400 from Huntsman.

Any compound that catalyses the isocyanate trimerization reaction (isocyanurate- formation) can be used as trimerization catalyst in the process, such as tertiary amines, triazines and most preferably metal salt trimerization catalysts. The metal salt trimerization catalyst is a carboxylate, the carboxylate group having 1-12 carbon atoms. Such catalysts are selected from alkali metal carboxylates, quaternary ammonium carboxylates and mixtures thereof, the carboxylate group having 1 -12 carbon atoms. Examples of suitable metal salt trimerization catalysts are alkali metal salts of organic carboxylic acids.

Preferred alkali metals are potassium and sodium, and preferred carboxylic acids are acetic acid and 2-ethylhexanoic acid. Most preferred metal salt trimerization catalysts are potassium acetate, potassium hexanoate, potassium 2-ethylhexanoate, potassium octoate, potassium lactate, N-hydroxypropyl trimethyl ammonium octoate, N-hydroxy- propyl trimethyl ammonium formate and mixtures. Two or more different trimerization catalysts can be used.

The metal salt trimerization catalyst is generally used in an amount of 0.01 -5% by weight based on the weight of the polyisocyanate and the polyol, preferably 0.05-3% by weight. It may occur that the polyisocyanate and/or the polyol used in the process still contains metal salt from its preparation which may then be used as the trimerization catalyst or as part of the trimerization catalyst.

The polyisocyanate, the polyol and the trimerization catalyst may be combined with the mineral fibres to be bonded in any order. Preferably, the polyisocyanate, the polyol and the trimerization catalyst are combined in an initial step so as to form a reactive binder composition, which in a next step is combined with the mineral fibres. The preparation of the reactive binder composition may be done by combining and mixing the polyisocyanate, the polyol and the catalyst in any order, preferably at an initial temperature between 5°C and 40°C and more preferably between 10°C and 30°C. Preferably the polyol and the catalyst are combined and mixed first, followed by combining and mixing with the polyisocyanate. The combining and mixing of the polyisocyanate and the other ingredients preferably is conducted at ambient pressure and at a temperature between 5°C and 45°C and more preferably between 5°C and 30°C in order to avoid undesired premature reactions as much as possible. As mentioned before, the catalyst may already be present in the polyisocyanate and/or the polyol in a sufficient amount. In that case only the polyisocyanate and the polyol need to be combined and mixed. Optionally further ingredients and additives may be used in the polyisocyanate and binder composition such as, for instance, surfactants; catalysts enhancing the formation of urethane bonds, like tin catalysts like tin octoate and dibutyltindilaurate, tertiary amine catalysts like triethylenediamine and imidazoles like dimethylimidazole; fire retardants; smoke suppressants; UV-stabilizers; colorants; microbial inhibitors; degassing and defoaming agents; plasticizers and internal mould release agents.

Still further isocyanate-reactive chain extenders and cross-linkers having an average equivalent weight below 100 may be used, like ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butane diol, hexane diol, glycerol, trimethylol propane, sucrose and sorbitol. These chain extenders and cross-linkers preferably are not used or only to the extent as necessary in view of the fact that commercial grades of catalyst may contain such chain extenders and/or cross linkers. If used these chain extenders and/or cross linkers are not taken into account in calculating the aforementioned index: additional polyisocyanate is to be used to compensate for the active hydrogens in these chain extenders and cross-linkers.

The amount of binder is chosen on the basis of desired cohesion, strength and cost, plus properties such as reaction to fire and thermal insulation value. The lower limit of 1 wt % results in a composite with a lower strength and cohesion, which is however adequate for some applications, and has the benefit of relatively low cost and potential for good thermal and acoustic insulation properties. In applications where a high mechanical strength is needed, a higher amount of binder should be used, such as up to 30 wt %. For a majority of applications, a suitable composition will include a binder amount from 1 to 30 wt %, preferably from 1 to 20 wt% and, most usually, from 4 to 15 wt %.

Once the polyisocyanate and/or the binder composition according to the present invention has been prepared it may be allowed to react, preferably at an elevated temperature so as to form a polyisocyanurate. This next step is more preferably conducted at a temperature between 50°C and 350°C and most preferably between 70°C and 280°C. This reaction may take between 5 seconds and 10 hours and preferably takes between 15 seconds and 2 hours. The process may be conducted at ambient pressure or at reduced or elevated pressure.

Applying the reactive binder composition to the mineral fibres to be bonded may be conducted by coating, impregnating, mixing and spraying of the binder composition and combinations thereof and/or any other suitable way which ensures thorough contact between the reactive binder composition and mineral fibre material.

Example

In tests, aerogel particulate material of the type "Nanogel® Fine Particle Aerogel" from Cabot International was used and showed excellent results. The tests were carried out with stone wool fibres having a density of approximately 2,800 kg/m³.

The boards were made by crude mixing of equal amounts by weight of mineral wool fibres and aerogel particles. This mixture was fed into a disentanglement unit, resulting in a homogeneous mixture of the mineral wool fibres and aerogel.

The polyisocyanurate binder was mixed with the mineral wool fibres and aerogel mixture by injecting the binder into the primary air flow by means of a nozzle.

The binder was formed by two components. One component contained the emulsifiable polyisocyanate. The other component was a water based suspension of additives. Both components were dosed with pumps.

The mixture of fibres, aerogel and binder was transported by the secondary air flow in a sifter and fed to a cyclone. The cyclone separated the solid material from the airflow. The mixture was collected directly in the mould that was used to press cure the mixture during 5 minutes at 160 °C. Two boards were made with a nominal content of stone wool of 40 wt%, a Nanogel® content of 40 wt% and 20 wt% polyisocyanurate-forming binder as a two-component binder.

The thicknesses of the boards were 9.9 and 10.4 mm, the densities were 202 and 201 kg/m³, respectively. The thermal conductivities were found to be 23.8 and 24.0 mW/m K, respectively.

The boards were easy to handle without damaging the boards and showed enough strength to be self-supporting.

Claims

C L A I M S

1 . A method for manufacturing a self-supporting aerogel-containing composite, said method comprising the steps of:

providing mineral fibres in an amount of from 3 to 80 wt % of the total weight of starting materials,

providing an aerogel particulate material in an amount of from 10 to 75 wt % of the total weight of starting materials,

providing a binder in an amount of from 1 to 30 wt % of the total weight of starting materials, wherein the binder is a polyisocyanurate-forming binder,

suspending the fibres in a primary air flow and suspending the aerogel particulate material in the primary air flow, thereby mixing the suspended aerogel particulate material with the suspended fibres,

mixing the binder with the mineral fibres and/or aerogel particulate material before, during or after mixing of the fibres with the aerogel particulate material,

collecting the mixture of mineral fibres, aerogel particulate material and binder and pressing and curing the mixture to provide a consolidated composite with a density of from 100 kg/m³ to 800 kg/m³, such as 120 kg/m³ to 400 kg/m³.

2. A method according to claim 1 , wherein the mineral fibres are provided in the form of a collected web and the method further comprises subjecting the collected web of fibres to a disentanglement process.

3. A method according to claim 2, wherein the disentanglement process comprises feeding the web from a duct with a lower relative air flow to a duct with a higher relative air flow.

4. A method according to claim 3 wherein the speed of the higher relative air flow is from 20 m/s to 150 m/s, preferably from 30 m/s to 120 m/s, more preferably from 40 m/s to 80 m/s, most preferably from 50 m/s to 70 m/s.

5. A method according to any of claims 2 to 4, wherein the disentanglement process comprises feeding the collected web to at least one roller which rotates about its longitudinal axis and has spikes protruding from its circumferential surface.

6. A method according to any preceding claim, wherein the roller has a diameter based on the outermost points of the spikes of from 20cm to 80cm, preferably from 30cm to 70cm, more preferably from 40cm to 60cm and most preferably from 45cm to 55cm.

7. A method according to claim 5 or claim 6, wherein the roller rotates at a rate of from 500 rpm to 5000 rpm, preferably from 1000 rpm to 4000 rpm, more preferably from 1500 rpm to 3500 rpm, most preferably from 2000 rpm to 3000 rpm.

8. A method according to any of claims 5 to 7, wherein the outermost points of the spikes of the roller move at a speed of from 20 m/s to 150 m/s, preferably from 30 m/s to 120 m/s, more preferably from 40 m/s to 80 m/s, most preferably from 50 m/s to 70 m/s.

9. A method according to any of claims 2 to 8, wherein the aerogel particulate material is added to the collected mineral fibre web prior to the fibre disentanglement process and is suspended in the primary air flow together with the disentangled fibres.

10. A method according to any of claims 2 to 9, wherein the mixture of mineral fibres, aerogel particulate material and binder is subjected to a further fibre disentanglement process after the mixture has been suspended in the primary air flow, but before the mixture is pressed and cured.

1 1 . A method according to any preceding claim, wherein at least part of the aerogel particulate material is carried to the primary air flow as aerogel particulate material suspended in a tributary air flow and the method comprises combining the tributary air flow with the primary air flow and thereby mixing the aerogel particulate material with the fibres.

12. A method according to any preceding claim, wherein the mineral fibres, binder and aerogel particulate material, when suspended in the primary air flow, are subjected to a further air flow in a different direction to the primary air flow.

13. A method according to claim 12, wherein the primary air flow is generally lateral and the further air flow is generally upwards.

14. A method according to any preceding claim, wherein the primary air flow has an initial speed of from 20 m/s to 150 m/s, preferably from 30 m/s to 120 m/s, more preferably from 40 m/s to 80 m/s, most preferably from 50 m/s to 70 m/s.

15. A method according to any of claims 12 to 14 wherein the further air flow has a speed of from 1 to 20 m/s, preferably from 1 to 13 m/s, more preferably from 2 to 9 m/s, most preferably from 3 to 7 m/s.

16. An aerogel-containing composite obtainable by the method according to any of the preceding claims.

17. An aerogel-containing composite comprising: mineral fibres in an amount of from 3 to 80 wt % of the total weight of starting materials, aerogel particulate material in an amount of from 10 to 75 wt % of the total weight of starting materials, a

polyisocyanurate-based binder in an amount of from 1 to 30 wt % of the total weight of starting materials, wherein the composite is substantially homogeneous and is cured and pressed to a density of from 100 kg/m³ to 800 kg/m³, such as 120 kg/m³ to 400 kg/m³.