INSULATION BOARD

The present invention relates to an insulation board comprising an insulation material and a coating.

In the countries of the European Community, a uniform, harmonized fire testing method for thermal insulations has been built up for more than 15 years. The content of the most demanding class A-1 in the EU fire classification is briefly that the calorimetric potential (PCS) of the insulation material must not exceed the value 2 MJ/kg. According to the norm, a coated insulation product in which the actual insulating material layer is in the fire class A-1 , obtains the fire class A-1 without a separate test, if the fire load of the coating does not exceed the value 2 MJ/kg (the coating is considered a non-essential component whose thickness is less than 1 mm). Thus, only the calorimetric potential of the coating must be tested.

Mineral wood alone meets the classification A-1 , but not with any coating. However, a coating is necessary and/or useful in view of the best possible performance of the insulation.

With the method presented in this application, it is possible to manufacture a film product whose calorimetric potential is less than or equal to 2 MJ/kg.

In Europe, a British fire testing method is also used (BS476 Part 6 - 7 Fire Propagation Test), according to which testing the insulation material must achieve Class 0. With the method presented in this application, it is also possible to manufacture a thermal insulation board whose insulation material is phenolic foam insulation and which meets the requirements of Class 0.

The thermal insulation board according to the invention is characterized in that the insulation material is phenolic foam insulation and the coating is a film product comprising an aluminium foil and a fibre-containing layer, which are attached to each other with an

adhesive so that the adhesive is applied onto the fibre-containing layer which is attached by said adhesive to the aluminium foil.

The fibre-containing layer referred to in this application may be a glass fibre mesh, a non-woven fabric containing glass fibres (glass fibre felt), or a polyester mesh.

Phenolic foam insulation is fire-resistant, but after it has caught fire, it will, however, bum. Therefore, the particular advantage of phenolic foam insulation lies in the fact that by using it, a delay can be provided in the initial situation of a fire. What is more, phenolic foam insulation does not produce such toxic combustion gases as polyurethane insulation does.

The idea of the invention is that the fire load of the thermal insulation board can be made low, when adhesive is applied to only those points where the aluminium film and the fibre-containing film are attached to each other; for example, a non-adhesive area is left between the openings of the glass fibre mesh. Furthermore, the amount of adhesive used for the attaching is small. Consequently, by limiting the content of organic substance in the product, the best fire class is achieved without using fire retardant chemicals. Yet another advantage is that the bare aluminium foil between the openings of the glass fibre mesh has a very high surface energy, wherein e.g. adhesives adhere to it well.

The film product used as a coating for the thermal insulation board comprises an aluminium foil and a fibre-containing layer, normally a glass fibre mesh, which are fastened to each other by adhesive. The square mass of the aluminium foil is normally 45 to 55 g/m ² .

The glass fibre mesh is normally a mesh composed of glass fibre threads, with threads in longitudinal and cross directions. The square mass of the glass fibre mesh is normally 10 to 15 g/m ² , and its mesh size is preferably 5 to 10 mm x 10 mm. The square mass of the glass fibre mesh may also be greater than that mentioned above, and its mesh size may be, for example, 3 mm x 3 mm when the level of

Class 0 is aimed at. The fibre material of the glass fibre mesh is normally E glass whose fineness may be 30 to 40 tex (tex = g/km).

The glass fibre mesh is held together by means of adhesive. The adhesive used at the stage of manufacture of the glass fibre mesh may be polyvinyl alcohol or suitable waterproof adhesive.

Instead of the glass fibre mesh, it is possible to use a sufficiently open non-woven fabric containing glass fibres (glass fibre felt), in which case the quantity of organic substance must also be kept on a sufficiently low level. Furthermore, in some applications, it is possible to use a polyester mesh instead of a glass fibre mesh.

According to the first embodiment of the invention, the film product is made so that a hot-melt adhesive in molten state is applied onto the glass fibre mesh, and the glass fibre mesh is fastened to the aluminium foil. The hot-melt adhesive may contain ethyl vinyl alcohol, resin and wax. The content of the hot-melt adhesive is normally 1 to 2 g/m ² so that the total content of the adhesive used at the manufacturing stage of the glass fibre mesh and the hot-melt adhesive does not exceed

3 g/m ² , when the aim is to achieve EU A-1 class, but when Class 0 is aimed at, the content of the adhesive may be higher.

According to a second embodiment of the invention, the film product is made so that the adhesive applied at the manufacturing stage of the glass fibre felt is also used for attaching the glass fibre mesh to the aluminium foil. In other words, the manufacture of the glass fibre mesh and the fastening of the aluminium foil are integrated in a single process, wherein the adhesive in adhesive state can also be used for fastening the aluminium foil. The adhesive used may comprise polyvinyl alcohol, and its content, calculated on dry substance, is not more than 3 g/m ² , when EU A-1 class is aimed at, but when Class 0 level is aimed at, the content of the adhesive may be higher.

According to a third embodiment of the invention, the film product is made so that the glass fibre mesh is made ready and the adhesive

contained in it is dried. The adhesive may comprise polyvinyl alcohol, and its content, calculated on dry substance, is not more than 3 g/m ² , when EU A-1 class is aimed at, but when Class 0 level is aimed at, the content of the adhesive may be higher.

When the glass fibre mesh and the aluminium foil are integrated, the adhesive in the glass fibre mesh is moistened, for example by spraying water onto the glass fibre mesh. The adhesive is thus made tacky again, and the glass fibre mesh is fastened onto the aluminium foil and dried. In addition to the glass fibre mesh, said methods can also be applied to a non-woven fabric or a polyester mesh that contains glass fibres.

The film product according to the invention can be used as a coating applied onto mineral wool, as a coating applied onto phenolic foam insulation, or as a material for a tape intended for the fastening of thermal insulations or for the sealing of structures. In the tape use, the film product has a particular advantage in addition to the fire properties: Previously, tapes have been made by extruding a plastic layer onto an aluminium foil and a glass fibre mesh. When an adhesive has been applied onto the plastic layer, its solvent substances have migrated between the aluminium foil and the plastic layer, detaching them from each other. Now, when the adhesive can be applied directly onto the aluminium foil (because the aluminium surface is exposed at the openings of the glass fibre mesh), no layers remain on the tape which might detach later on. The adhesive used in the tape is normally an adhesive that will be cross-linked further in course of time. The thickness of the adhesive layer may be 60 to 80 μm.

In the following, we shall discuss a situation in which the film product is used as a coating for a phenolic foam insulation. The phenolic foam insulation is formed by a condensation reaction in which water is produced. Consequently, the water must be removed from the insulation by keeping it at a mild temperature of, for example, 80 to 9O ⁰ C for about one day. When the phenolic foam insulation has a coating, the removal of water must be taken into account in the

structure of the coating. The coating may be, but does not need to be perforated, because the moisture may also move in and out of the product along the fibres of the fibre-containing layer, such as the glass fibre mesh.

When the film product is fastened to the phenolic foam insulation, the moisture in the phenolic foam insulation may activate the adhesive in the fibre-containing layer, such as the glass fibre mesh, if the adhesive is water soluble. Thus, the adhesive helps to fasten the coating to the insulation. If, on the other hand, the adhesive contains a hot-melt adhesive, the adhesive is fastened to the phenolic foam insulation when the insulation is dried at a raised temperature and the water has substantially exited the insulation. Because the film product is fastened onto the surface of the phenolic foam insulation during its formation, the phenolic foam insulation also penetrates around the threads of the mesh or non-woven fabric, so that the coating is also attached by this mechanism, in which case the surface resistance of the product is also improved. Furthermore, if the film product is also perforated, the phenolic foam insulation will penetrate into these perforations at the stage when they are formed, in which case, again, fastening points are formed between the coating and the phenolic foam insulation.

The diameter of the perforations in the film product may be 0.1 to 1.2 mm, preferably 0.4 to 0.6 mm. The number of perforations is normally 2 to 4 per cm ² .

In the following, we shall discuss the film product used as a coating for the insulation by means of an example and a drawing. The drawing shows the process of manufacturing a film product according to the first embodiment.

Example.

The raw materials for the film product were the following:

Aluminium foil - thickness 18 μm

- square mass 49 g/m ² Hot-melt adhesive - applied content 1.5 g/m ² Glass fibre mesh

- thread 34 tex glass fibre thread (E glass) containing more than 200 filaments

- mesh size 5 mm x 10 mm - square mass 11 g/m ²

- 1 to 1.5 g/m ² of organic adhesive in the glass fibre mesh

According to a measurement by VTT Technical Research Centre of Finland (RTE 59/04), the calorimetric potential of the film product is 1.3 MJ/kg.

When Class 0 level is aimed at, the film product being a coating for phenolic foam insulation, the glass fibre mesh may have a denser mesh size, for example 3 mm x 3 mm. The content of the hot-melt adhesive may also be higher, for example 6 to 10 g/m ² .

The drawing shows the manufacturing of a film product according to the first embodiment. A tank contains hot-melt adhesive 1 at a temperature of about 160°C. A roll 2 takes hot-melt adhesive 2 onto its surface. The roll 2 rotates at a speed that is about 10% of the web speed.

From the roll 2, the hot-melt adhesive is transferred onto a roll 3 which is preferably a rubber roll. Between the rolls 2 and 3, there is an adjustable nip where excess hot-melt adhesive is pressed out. The roll 3 rotates at a speed that is about 90 % of the web speed. From the surface of the roll 3, the hot-melt adhesive 1 is transferred onto a glass fibre mesh 4 whose web speed is about 150 m/min. The contact angle between the roll 3 and the glass fibre mesh is normally 10 to 15°.

An aluminium foil 6 is introduced onto the roll 5. The temperature of the roll 5 is about 8O ⁰ C, so that the aluminium foil 6 is heated and the glass fibre mesh 4 adheres easily onto the aluminium foil 6. Thus, the film product 7 is formed.