The present invention relates to a method of preventing or delaying delamination of a fire protection staicture, according to the preamble of Claim 1.

The present invention also relates to a multi-layer board which is used as a fire protection board, according to the preamble of Claim 20, and a use according to Claim 22.

Board structures which are used as fire protection boards are typically comprised of a body layer and a metal layer, for example a metal board or a metal film, which is arranged at a distance from the body layer. During use, the metal layer protects the body layer in case of fire.

Between the metal film and the body layer, there is at least one but often several polymer layers which bind the structure together, but which may also serve as an insulating layer that reduces the heat flux passing through the board.

In wood-based multi-layer structures, the body layer consists of a wood board. US Patent Specification No. 6,511,730 describes a composite board which is comprised of several layers and which comprises a fire retardant.

Published DE Patent Application No. 2019770 describes a non-combustible laminate which is comprised of 7 layers. The layers are attached to each other by means of adhesive layers.

US Patent Specification No. 4,935,281 describes a board structure which is protected against fire and which is comprised of an inner layer of plywood, an intermediate layer of metal, a glass fibre fabric and adhesive layers.

Prior art structures have good short-term fire protection properties, but at the same time it has been found that multi-layer structures are susceptible to the layers becoming detached, i.e. delamination. This reduces the capacity of the structures for fire protection, because air penetrates between and under the layers. The present invention is based on the idea that a fire retardant is included in at least one polymer layer of a structure which is comprised of several sub-layers on top of each other, such as a multi-layer board intended to be used as a fire protection board. In addition, or alternatively, the fire retardant can also be included in the inner layer, which is arranged against the first layer, i.e. the innermost polymer layer.

Surprisingly, it has been found that the fire retardants as such do not affect the strength properties of the polymer layer within a temperature range which extends from room temperature up to the manufacturing temperature of the polymer (for example to the melt- processing-temperature). At high temperatures, i.e. above approximately 500 °C, in particular above approximately 800 °C, fire retardants, however, significantly improve the holding together of the structure of the polymer, and thus prevent delamination of the structure, in particular detachment of the fire protection layer from the body board.

More specifically, the method according to the present invention is mainly characterized by what is stated in the characterizing part of Claim 1.

The multi-layer board according to the present invention is, in turn, characterized by what is stated in the characterizing part of Claim 20, and the use according to the present invention, by what is stated in Claim 22.

Considerable advantages are achieved with the present invention. Thus, delaying or preventing delamination can significantly slow down the break-up of the board at high temperatures, because the actual fire protection layer, such as a metal film, remains in place longer and thus protects the other layers.

By using, between the outer and inner layers, such an intermediate layer which is comprised of a non-woven fabric layer and a thermoplastic polymer film, a multi-layer structure that holds together very well is obtained. The thermoplastic polymer film is highly malleable and, when heated, conforms to the adjacent layers, and thus protects them firmly, in particular it protects the inner layer. The non-woven fabric layer of the intermediate layer, in turn, supports the thermoplastic layer. Fire retardant can be easily added to the thermoplastic polymer film, for example, during preparation of the film. In the following, the present invention will be examined in more detail with the help of a detailed explanation and with reference to the accompanying drawing. Figure 1 shows a side view of one of the embodiments of the board according to the present technology, and

Figure 2 shows a corresponding view of another embodiment according to the present technology. In the present context, "composite board" refers to any combination board which is composed of layers ^" which are formed of wood-based ^ ^{^} material and at least one other material layer.

In the present context, "wood-based material" refers to any material which is composed of any wood material or materials that are based on wood fibres, for example wood veneer, such as softwood or hardwood veneer, or a multi-layer board, plywood or wood board or a similar wood-based material, such as blockboard, chipboard, fibreboard, including MDF and OSB.

In the present context, "adhesive layer" refers to any intermediate layer which joins together the different materials, and which is comprised of adhesive material, which is known per se, for example resin, phenol-formaldehyde adhesive, melamine-formaldehyde adhesive, urea- formaldehyde adhesive and/or polyurethane adhesive or any other adhesive material which is suitable for the purpose.

In the present context, "one-time compression" refers to a method in which all the desired component layers, i.e. material layers and adhesive layers, are stacked at the same time to form a preform, and a board is generated in a one-time compression step.

As described above, the present technology refers in particular to the use of fire retardant in the binder layers of a multi-layer structure, or in such a surface of this kind of structure, in which the metal layer is attached for example by means of the binder layers.

Typically, the film which is used as a fire protection layer, such as a metal film, is thin (thickness approximately 0.005-0.5 mm, in particular 0.005-0.1 mm), in which case it can also be used for protecting 3D shape surfaces and edges, or to protect edges which can be machined.

However, according to a more preferable embodiment, a solution according to the present invention is used in a multi-layer structure which comprises structural surfaces that are at least essentially laminar. Examples of these are different building boards and similar structures which are essentially stiff and typically self-supporting.

In one embodiment, the structure comprises a body board, such as a wood plate, or the like. At a certain distance from the body board, a fire protection layer is arranged which is comprised of a metal layer or a similar material. Between the layers, there is an

intermediate layer which comprises a binder. In at least one binder layer of this multi-layer board structure, or in a non-woven layer or in a combination of these, there is fire retardant, in order to prevent or delay, under conditions of fire, delamination of the multilayer board structure.

Figure 1 shows a diagram of an embodiment of the multi-layer board structure. In this embodiment, the board structure is comprised of

- an outer layer 1 ;

- a first polymer-based adhesive layer 2,

- a non-woven fabric which is comprised of a polymer 3;

- a second polymer-based adhesive layer 4; and

- an inner layer 5.

The body layer of wood-based multi-layer structures is comprised of a wood board or a similar wood-containing board. The outer layer acts in principle as a fire protection layer, and is therefore made of a material which is able to withstand temperatures of above 500 °C, in particular above 750 °C, most suitably above 900 °C, for a period of at least 10 seconds, in particular at least 60 seconds, most suitably at least 120 seconds. The outer layer 1 is a thin layer or film. Typically, this consists of a metal, such as aluminium, copper or steel, or films or composite materials which comprise metals or metallic substances, or other materials that withstand fire and high temperatures.

In a preferred embodiment, a metal film is used. The thickness of the metal film is preferably approximately 0.005-3 mm, in particular approximately 0.005-1.5 mm.

In addition to the metal layers, in principle it is possible to use ceramic materials, and films and non-woven layers that are impregnated with ceramic materials. The thicknesses of these layers when used as fire protection layers are usually 0.1-15 mm, in particular approximately 0.5-10 mm.

The surface of the outer layer may have a lacquer layer (not shown) or a similar surface- treated layer, which provides the board structure with a desired finish and, if needed, permits printability.

The inner layer 5 is most suitably a board, in particular a structural board, which is capable of giving the board according to the present technology, desired mechanical properties, such as sufficiently high stiffness, flexural strength and impact strength, or a combination thereof.

Preferably, a board which is wood-based acts as the inner layer which, within the framework of the above mentioned definition - according to the first embodiment of the technology - means that the board is entirely comprised of wood, and according to another preferred embodiment, the board is comprised of wood layers, wood battens, plywood, veneers, fibres, chips or similar wood particles, or these are included in the board. A wood- based frame is for example a wood board, wood-fibre board, or a plywood or composite board that is composed of layers of plywood or veneer on top of each other.

Typically, the wood parts are attached to each other by means of an adhesive, for example, by mixing the wood parts in the adhesive, or by applying adhesive between adjacent wood layers or wood-containing layers, in particular in the form of adhesive layers. In one preferred embodiment, the adhesive layers are uniform. They may be formed of adhesive films. In another embodiment, the adhesive layers are comprised of separate adhesive zones, 5 ΰ1ι as adhesive strips. In other respects, with regard to the adhesive layers, reference can be made to the definition above.

The multi-layer boards are preferably manufactured by using a one-time compression (see above), but it is also possible to generate a multi-layer board by stacking together individual layers, in which case one composition is compressed at a time. Wood-based multi-layer boards can comprise, besides layers of wood or layers of wood parts, also functional layers. Examples of the properties of such layers are the following: thermal insulation, a moisture barrier, impermeability to air, fire protection, mechanical stress resistance, chemical resistance, weather resistance, and combinations thereof.

With regard to the structures of functional multi-layer boards, and the production and the properties of them, reference can be made to our parallel patent applications nos. WO 2011/101546 and WO 2011/131846.

^{^} ln a preferred embodhnent— the-non=woven-layer-which-forms-the-inner layer is preferably a plywood board, which is typically made of several layers of wood veneer, on top of each other, and which are attached to each other by means of adhesive layers. The thicknesses of the individual wood veneer layers are approximately 0.1-5 mm, for example

approximately 0.2-3 mm.

The additional inner layer, i.e. body layer 5, may be made up of wood-based boards, can comprise a mineral material, which may include or consist of silicates or similar silicon oxide materials, or other inorganic, preferably essentially non-combustible materials, such as calcium salts, for example gypsum.

In the embodiment according to Figure 1, reference numerals 2 to 4 together indicate the intermediate layer of the present board. This layer binds together the outer layer and the inner layer.

Most suitably, the intermediate layer comprises a fabric layer, in which case the fabric structure renders to the fabric intermediate layer 3 good mechanical properties. One example of a suitable fabric is the non-woven fabric 3 shown in Figure 1. Typically, the non-woven fabric is an inorganic or organic material, in particular polymer, such as polyester. Examples are poly-terephthalate fabrics.

Furthermore, the intermediate layer also comprises adhesive layers. There is one or more of these. Most suitably, as shown in Figure 1, there is one adhesive layer on each side of the fabric intermediate layer 3 (reference numbers 2 and 4). The adhesive layers are typically selected from a group which is comprised of

thermosetting adhesive or thermoplastic adhesive resins, such as phenol formaldehyde (pf), melamine formaldehyde (mf), urea-formaldehyde (uf), polyurethane (pu), methylene diphenyl diisocyanate (mdi), polymeric methylene diphenyl diisocyanate (pmdi) or water- based methylene diphenyl diisocyanate (emdi) or ethylidenebis(2.5-furandiylmethylene) diisocyanate (edfi) or a mixture thereof. Other particular examples are dispersions of emulsion polymer isocyanate and polyurethane hot-melt adhesives. In addition to the abovementioned layers, the board in the intermediate layer may also comprise at least one polymer film (in Figure 2) which can be arranged in a desired gap, for example against the outer layer 11, typically between the outer layer 11 and the first adhesive layer 12. Alternatively, the polymer film can be arranged against the inner layer 16, typically between the inner layer 16 and the adhesive layer 15. It is also possible to arrange the polymer film layer against the fabric layer 13, or between the fabric layer 13 and the adjacent adhesive layer 12 or 14. In this figure, it is arranged between the fabric layer 13 and the second adhesive layer 15. There may be several polymer films in the structure.

A suitable polymer film is made of thermoplastic. The thickness of such a thermoplastic film is approximately 0.1-10 mm, in particular approximately 0.5-5 mm. Most suitably, the thermoplastic used is an engineering plastic, such as polyolefin, polyester, polyimide, poly amide, ABS plastic or similar.

Fire retardant is included in at least one layer, which is selected from a group that is comprised of the first and the second adhesive layer and the thermoplastic polymer film.

In another embodiment, fire retardant is included in the inner layer or its surface.

Fire retardant is included in the adhesive layer, the polymer layer and/or the surface of the inner layer, in order to prevent delamination of the structure, particularly to protect the join between the surface layer 1, such as a metal film, and the inner layer, under conditions of fire or more generally under conditions in which the structure is exposed to high

temperatures. Most suitably, the present technology prevents, under conditions of fire, detachment of the metal film or the like from the inner layer. In principle, a fire retardant agent is included in at least one polymer layer, but in one embodiment, a fire retardant is included in at least two layers of a multi-layer board structure, of which layers at least one is a polymer layer.

Typically, a mineral fire retardant or an organohalogen compound or an organophosphorus compound, or a combination thereof, is used as the fire retardant.

In particular, aluminium hydroxide, alkaline earth metal hydroxide, magnesite,

wollastonite, talc, antimony oxide, boron compound, such as borate, or inorganic ^■" phosphorus -compound or organobromine ora brominated polymercompound or organophosphate, organophosphonate, or organophosphinate, are used as a fire retardant.

Approximately 0.001-35 %, in particular approximately 0.01-20 % of fire retardant is included in the polymer layer or the surface of the inner layer, in which case the amount of fire retardant is calculated based on the total weight of the layer in which the fire retardant is included.

Mineral fire retardants are most suitably used in a finely divided form, and, typically, mineral fire retardant is used in a particle or granular form.

The average particle size of the powder or the granules is approximately 0.1 μιτι-10 mm, in particular approximately 0.01 mm-5 mm. Organic fire retardants can also be used in the form of liquid solutions and suspensions, Water or an organic solvent can be used as an intermediate agent for these solutions or suspensions. Typically, the concentration of fire retardant in the solutions or suspensions is approximately 0.1-99 % by weight, particularly approximately 1-90 % by weight, most suitably approximately 5-75 % by weight, of the total weight of the solution or suspension.

Case specifically, at the temperature at which the organic fire retardants operate they are already in a liquid state.

Compositions which are in the form of a solution or a suspension can be used in combination with, for example, materials that form adhesive layers by mixir

materials with each other. Thus, in one preferred embodiment, a modified adhesive composition is generated which is comprised of a dispersion of emulsion polymer isocyanate, or a polyurethane hot-melt adhesive, which contains a fire retardant. In such a composition, the fire retardant percentage is in particular approximately 0.001-35 % by weight, preferably approximately 0.01-20 % by weight, as described above.

Compositions which are in the form of a solution or a suspension can also be used for treatment of the surface of the inner layer. In this case, the application amounts are for example approximately 0.1-400 g, in particular approximately 1-100 g, most suitably approximately 1-50 g of fire retardant per m ² , depending on the fire retardant used.

When there is a polymer film in the intermediate layer, the fire retardant is preferably added already during preparation of the film. The film surface can be treated for example with compositions which comprise compatibilisers, in particular liquid fire retardant compositions which comprise reactive compatibilisers.

Preferably, the fire retardant is added to the thermoplastic polymer film during melt- processing. Accordingly, the fire retardant can be included during the compounding process of the thermoplastic raw material, either as such with the plastic raw material, or together with the other additives, such as fillers and auxiliary agents. More preferably, the fire retardant is mixed into a polymer mass which is to be extruded, from which the polymer layer of the multi-layer board structure is generated. The polymer film can be extruded directly onto the surface. This significantly speeds up the production of the board.

It is also possible to produce the films by using the blown film or the flat film method and then separately attaching them to the surface. Typically, the film is attached for example to the surface of wood by first priming the surface and then adding to the primed layer an adhesive plastic layer that adheres to the primer. After that, the body plastic and, optionally, the surface plastic which has functional properties, are attached.

The board structure according to the present invention can be produced all together by using one-time compression. It is also possible to separately produce the body layer and the outer layer together with the intermediate layers, which are then attached to each other, for example, by stacking them into a preform and then pressing them together.

In an example, a multi-layer board is produced which is comprised of

- a lacquer layer;

- aluminium layer;

- an adhesive layer for the aluminium layer;

- a polyethylene film,

- a non-woven layer that is comprised of polyester;

- an adhesive layer for the non-woven layer; and

- a plywood board.

An aluminium film having a thickness of 30 μιη acts as the surface layer. The film is attached to the non-woven fabric, which is made of polyester and the grammage of which is approximately 25 g/m ² . The film is attached by using a binder layer or an adhesive layer which is comprised of polyethylene, and the grammage of which is 23 g/m ² .

After that, the surface layer is glued to the board by using a weather-resistant polyurethane adhesive, for example a hot-melt adhesive, 60-120 g/m ² of which is applied between the plywood board and the surface layer.

Polyurethane hot-melt adhesive gives extremely good results in fire tests.

The non-woven board comprises 1.4 mm birch-veneer layers which are glued together using a weather- and steam-resistant phenolic resin adhesive.

The edges of the board are sealed with acrylic paint.

Reference Numerals List 1; 11 outer layer

2; 12 first adhesive layer

3; 13 non- woven fabric

4; 15 second adhesive layer

14 polymer layer 5; 16 inner layer

Citations

Patent Literature

US 6 511 730

DE 2019770

US 4 935 281

WO 201 1/101546

WO 2011/131846.