Traditionally, many roofs are covered with flexible roof coverings in the form of waterproof sheets. As it is generally known, roof structures normally are insulated e. g. using mineral fibre mats foam insulating sheets or other type of insulation materials. This insulating material may be covered with a roof support layer, which is relatively stiff and sufficiently strong to wear a roof covering sheet. In some situations the roof support layer is constituted by a layer of insulation material.

In practice a layer of insulating material constituting a roof support must itself be sufficiently stiff and strong so that it is possible to walk on the roof. Onto the roof i. e. onto the roof support layer or directly onto the roof insulating material, a roof covering is applied. One of the most common roof coverings in the prior art is bituminous roof covering. When applying such bituminous roof coverings, a bituminous layer is applied and rolled or spread over the total area of the roof. In order to fixate the bituminous layer, heat is applied in order to heat seal the bituminous layer onto the roof.

In practice, this step of heating is conducted using a flame heater, such as a gas burner, and during this step there is a large risk that a roof fire is initiated.

Furthermore, bituminous material is very cumbersome to

work with due to degassing during the sealing of the bituminous layer to the roof.

It has also been suggested to use a self adhesive sheet based on bitumen as a roof covering, and thereby avoiding the heat sealing step. Such a material is e. g. disclosed in GB-A-2 305 667, and DD-A5-DD 295 179. Bituminous self-adhesive compositions of this type have in practice only found use in the repairing of existing roof coverings, and can in general not be used for application onto an uncovered roof. In particular, such bituminous self-adhesive compositions cannot be applied directly onto an insulating layer because the adherence to such a layer is unacceptable low.

In order to provide a waterproof sealing to the environment, it is necessary to provide a strong bonding between the roof covering sheet and the roof surface e. g. a mineral fiber board. In the prior art methods, the only roof covering material, which has been able to provide a sufficiently strong bonding, is roof covering based on bitumen and heat sealed to the roof.

Another type of roof coverings used in the invention is roof covering in the form of polymeric foils. Such known roof covering foils are e. g. prepared of PVC, CPE, TPO or EDPM. According to prior art, such foils may be fixated mechanically or may be adhered onto a roof structure e. g. by using a self adhesive composition applied onto the foils or by using a curable adhesive applied onto the roof structure and/or onto the foil immediately before the application. When fixating a roof covering foil mechanically, it is necessary to penetrate the foil with nails, which increase the risk that water may penetrate into the insulating material and the lower roof structure.

Using curable adhesives are in general very cumbersome, and such adhesives normally comprise large amounts of organic solvents, which evaporate during the applications.

PCT application 98/31895 discloses a composite roof system comprising applying a curable or contact adhesive onto an insulating board after the board is build into the roof, and a foil e. g. a PVC sheet is applied onto the adhesive. This system may result in high peel strength between the insulating board and the foil, but as mentioned above, it is very cumbersome to work with liquid adhesive on site and consequently also very expensive due to the use of many man hours on site.

The known self adhesive compositions suggested for use in adhering foils to roof structures are in general adhesives, which provides a strong bonding to the foil.

But none of the adhesives suggested are able to provide a sufficiently strong bonding to a roof structure in the form of an insulating layer, and particularly not when the insulating layer is a mineral fibre layer.

A waterproof sealing to the environment is also necessary on front walls of buildings. Such front walls are normally insulated by applying an isolating layer onto the outer side of the wall structure, and covering this insulating with a covering layer. The bonding of the covering layer is essential to the durability of the insulating.

Also when isolating floors or inner walls of building, the peel strength between a covering placed onto the insulating and the insulating should be sufficiently

strong to withstand mechanical affects and variations in temperatures and air moisture.

The object of the present invention is to provide a method of adhering a covering to a insulating layer, in particular a mineral fibre insulating layer, also denoted an insulating board, and the method results in a strong bonding between the covering and insulating layer relatively to the known methods.

Another object of the present invention is to provide a method of adhering a covering to a insulating layer, in particular a mineral fibre insulating layer, where the method results in a water-tight and safe sealing of the covering layer to the insulating layer and which sealing has a high durability.

Yet another object is to provide a method of adhering a covering to a insulating layer, in particular a mineral fibre insulating layer, which method is simple and fast, and does not require the use of heat during the application.

These and other objects are achieved by the invention as defined in the claims.

The method according to the invention comprises the use of an adhesive selected between a nitrile adhesive, a silicone adhesive or a combination thereof. Surprisingly, it has been found that these adhesives are able to create a very strong bonding between a covering, such as a roof covering and an insulating layer or board. Also, it has been found that this strong bonding maintains its strength for several years, even when exposed to sun and wear.

According to the method of the invention, a covering having a first surface adapted to be bonded to an insulating layer on a building structure and a second surface adapted to turn away from the insulating layer, are adhered to the face surface of the insulating layer using the above-mentioned adhesives.

The adhesives used in the present method are selected between a nitrile adhesive, a silicone adhesive or a combination thereof. The nitrile adhesive comprises at least 20-by dry weight of one or more nitrile rubbers and one or more plasticizers selected between dialkyl sebacates, adipat and dialkyl phthalates, said alkyl groups independently of each other being methyl-, ethyl- or butyl groups. The silicone adhesive comprises at least 50 by dry weight of silicone rubber and an organic solvent for the silicon rubber.

In principle the nitrile rubber in the nitrile adhesive may include any kind of nitrile rubbers or combination of nitrile rubbers. Preferably the nitrile rubber in the nitrile adhesive is selected between methacrylonnitrile rubber, ethacrylonnitrile rubber, acrylonitrile rubber, or a combination thereof.

The nitrile adhesive preferably comprises between 25 and 50 _ and more preferably between 30 and 40 % by dry weight, and even more preferably between 35 and 40 by weight of nitrile rubber. The more nitrile rubber the adhesive comprises, the more plasticizer should be present in the composition. However, too much plasticizer can result in a very elastic and soft bonding with relatively low peel strength. The optimal amount of plasticizer is between 50 and 85 _ preferably 50-80 by dry weight, more preferably about 60-75 zu by dry weight

of the total dry weight of the adhesive. The plasticizer preferably comprises adipate or one or more dialkyl sebacates, and more preferably the plasticizer is dimethyl sebacate. Dialkyl phthalates is also very useful as plasticizer but due to its injurious effect on humans, it is not preferred to use dialkyl phthalates. In most cases adipate is the preferred plasticizer.

The nitrile adhesive preferably also comprises an organic solvent. This solvent is preferably selected between acetone, toluene and xylene. In order to obtain an adhesive, which is easy to apply due to a relatively low viscosity, the adhesive preferably comprises up to about 55 a by weight of the total weight of organic solvent.

Furthermore, the nitrile adhesive may comprise fillers including flame inhibitors, such as polyphosphate and magnesium hydroxide, and other ordinary fillers used in similar compositions. These fillers may be present in up to about 10 by weight of total weight and 55 %, preferably up to about 75 by dry weight of the adhesive.

The most preferred nitrile adhesive is the adhesive marketed under the trade name"Dunlop 6103", by Dunlop Adhesives.

The silicone adhesive comprises preferably at least 50% by weight, more preferably between 55 and 60 % by weight of silicone polymer and an organic solvent, preferably a solvent selected between toluene and xylene. The organic solvent should preferably be present in an amount of 35- 45 a by weight, more preferably about 40 ? by weight of an organic solvent

The silicone adhesive preferably comprises polydimethylvinylsiloxan, polymethylphenylvinylsiloxan, polydimethylsiloxan, or polydimethyldiphenylsiloxan.

Furthermore, the silicone adhesive may comprise fillers including flame inhibitors and other ordinary fillers used in similar compositions. These fillers may be present in up to about 10 % by dry weight of the adhesive.

Preferred silicone adhesives are marketed by GE Silicones under the trade names PSA 6571, PSA 518, PSA 595, PSA 605, PSA 750-D1, PSA 825-D1.

Both of the above type of adhesives are very weather and temperature resistant. In particular the silicone adhesive are resistant to temperature and can keep a high peel strength in temperatures as low as-100 °C and as high as 120 °C. The nitrile adhesive may work in the temperature interval between-5 to 80 °C.

The method may be carried out in four different modes. In the first mode, the"adhesive on cover mode"the adhesive is applied onto the first surface of the covering sheet, and the covering is applied onto the insulating layer, whereby the adhesive adhere the covering and the insulating layer together.

The face surface of the insulating layer may preferably be partly or totally covered with a layer of a primer, e. g. a polyvinyl acetate primer in thickness and patterns as described below. When the face surface of the insulating layer is covered with a primer, the adhesive layer on the covering sheet may be relatively thin, since the primer on the insulating layer reduces the amount of

adhesive adsorbed by the insulating material when the covering is applied onto said insulating layer.

In practice, it is preferred that the adhesive is applied onto the covering material in factory as a part of the manufacturing of the covering material. The adhesive is covered with a release layer, which does not stick to the adhesive. Such release layers are generally known in the art. After being covered with a release layer, the covering material is rolled onto itself. The rolling of the covering material is preferably performed so that the first side of the covering material, which is covered with the release layer, constitutes the outer side of the rolled covering material. The covering material in rolled form is very easy to transport. On site the rolled covering material is rolled onto the insulating layer to be covered. The release layer is removed either simultaneously with rolling the covering material onto the insulating layer or the release layer is removed after cutting and adjustment of the covering material.

In the second mode the"adhesive on insulation mode", the adhesive is applied onto the face surface of the insulating layer, and the covering material is applied onto the insulating layer, whereby the adhesive adhere the covering material and the insulating layer together.

In the third mode'the double sided tape mode", the adhesive is applied onto the insulating surface by removing one of the release layers from the double side tape. The double sided tape comprise a silicone or a nitrile adhesive on the side supposed facing the covering i. e. the upward facing side of the double tape.

Preferable the other side of the double tape i. e. the downward facing tape may preferably also comprise a

silicone or a nitrile adhesive, but alternative any other suitably adhesive may be used e. g. an acrylic adhesive.

With regard to the double side tape, the amounts applied to each side are very dependent of which adhesive is used. Generally the preferred amount adhesive one or more sides of the double tape of silicone or nitrile adhesive is between 50 to 180 g/m-dry weight. If using acrylic adhesive on the downward facing side of the tape, it is preferred to use the acrylic adhesive in an amount of between50 to 300 g/m-dry weight. The tape layer between the two adhesives can be a woven or a non-woven glass fleece, woven cotton-or polyester fleece.

In the fourth mode"the reverse coating mode", the adhesive is applied on to a release layer. The release layer has preferably different release effect on each side. The adhesive is applied to the side with the lowest release effect. The release layer with the adhesive is then rolled onto it self after the solvents have evaporated, and packed. In factory the rolled release layer is rolled out on to the insulating material, and the adhesive bonds to the surface of the insulation while the release layer remains adhered to the adhesive, thereby protecting the adhesive.

In practice, it is preferred that the adhesive is applied onto the insulating layer in factory as a part of the manufacturing of the insulating layers or boards. The adhesive is covered with a release layer, which does not stick to the adhesive. Such release layers are generally known in the art. After being covered with a release layer the insulating layer is build into the building structure, e. g. in the roof, walls or floor. The release layer is removed from the adhesive before applying the covering material onto the face surface of the insulating

layer. Preferably, the release layer is removed from the adhesive immediately i. e. up to about 10 minutes before applying the covering material onto the face surface of the insulating layer.

In the second mode, it is preferred that a primer is applied onto the face surface of the insulating material before applying the adhesive.

By applying a primer onto the face surface of the insulating material before applying the adhesive, dust is bonded to the insulating layer, and does therefore not interfere with the adhesive. Furthermore the amount of adhesive adsorbed by the insulating material is very reduced compared to an insulating layer not covered with a primer, thus the amount of adhesive applied onto the insulating layer may be reduced.

Preferably, the primer is cured prior to the application of the adhesive onto the primer layer. It is preferred that the primer layer is applied as a total or partly coating onto the insulating layer, more preferably in an amount of between 20 and 150 g dry stuff per m-. The most preferred primer is a primer of polyvinyl acetate.

The amount of adhesive applied onto the first surface of the covering material or onto the face surface of the insulating layer depends largely on the adhesive used.

The type of covering material and the type of insulating layer used, also influence the amount of adhesive necessary for obtaining a safe and strong bonding between the covering material and the insulating layer.

Generally, the preferred amount of adhesive applied in both the first and the second mode of the invention is between 20 and 200 g dry stuff per m-, and more preferred 50-150 g dry stuff per m-and e. g. 125 g per m-.

When the adhesive or at least the major part of the adhesive is a nitrile adhesive, the adhesive should preferably be applied in an amount of between 100 and 200 g dry stuff per m-, more preferably in an amount of between 125 and 175 g dry stuff per m-.

When the adhesive or at least the major part of the adhesive is a silicone adhesive, the adhesive should preferably be applied in an amount of between 20 and 100 g dry stuff per m-, more preferably in an amount of between 40 and 60 g dry stuff per m-.

In order to reduce the amount of adhesive necessary, it is preferred that only a part of the first surface of the covering material or the face surface of the insulating layer is covered with adhesive. However, in order to obtain a strong and safe bonding between the covering material and the insulating layer, the adhesive should preferably cover at least 40 and more preferably at least 60 M of the first surface of the covering material or the face surface of the insulating layer. The adhesive should preferably be applied in a pattern, more preferably in strips e. g. in straight or wave shaped, broken or unbroken strips, or in discrete punctiformed sub areas. Preferred patterns are preferably the patterns described in EP-A-0 005 812 and DE-A-3132637.

The covering material could in principle be any type of flexible roof coverings. If the covering material should be applied onto a front of a building or a roof, it should be able to provide a sufficiently barrier to the environment. Preferably, the roof covering is based on a polymeric sheet or several layered polymeric sheets optionally with intermediate layers of non-polymeric materials. Preferred polymeric covering material is

covering materials based on PVC, CPE, TPO, and EDPM.

Coverings containing phthalates are also very useful in the present invention, because it has been found that the adhesives used in the present invention provide a barrier for the phthalates. In other words, the phthalates in the covering materials do not migrate into or through the adhesive, and consequently, the amount of phthalates in such covering materials are very stable, whereby the covering material maintains its strength and flexibility for a very long time.

In principle the insulating material may be any kind of material, which is normally used in roofing structures, floors and wall structures, respectively. Preferably the insulating material is in the form of solid blocks, e. g. blocks having a thickness of at least 5 cm and a total dimension of at least 10x10x5 cm e. g. 60x120x10 cm. The insulating material may e. g. be a foam insulating material, a mineral fibre insulating material or a combination thereof.

It is preferred that the insulating layer or board is a mineral fibre insulating board suitable for building into a roof, a wall or a floor structure. Such boards of insulating materials are well known in the art. Preferred insulating boards are the roofing boards described in SE-416 719, DK-B-160 139, DE-A1-4 212 824, DK-B-148 121, US-A-1, 275, 957, US-A-4,950,355, DK-A-155 163, and DK PA-199900751.

The insulating layer or board is preferably a board comprising a layered body comprising a mineral fibre insulating layer having a mean density between 50 and 300 kg/m.

If the insulating layer is a wall insulating material, it should preferably have a density between 50 and 150 kg/m-, and more preferably be in the form of a duo layered product with a first layer having a density between 50 and 100 kg/m, e. g. about 60 kg/m, and a second layer having a density between 100 and 150 kg/m-, e. g. about 120 kg/m'.

If the insulating layer is a roofing or a floor insulating material, it should preferably have a mean density between 150 and 300 kg/m'and preferably including at least one rigid layer having a mean density of at least 450 kg/m-, said face surface preferably being a surface of said rigid layer. It is particularly preferred that a roofing or floor insulating material is in the form of a duo layered product with a first layer having a density between 75 and 150 kg/m, e. g. about 100 kg/m, and a second layer having a density between 400 and 600 kg/m, e. g. about 450 kg/m.

The invention also relates to the mineral fibre insulating board coated with the adhesive as described above, and preferably comprising an intermediate coating of a primer.

The primer layer could in principle be any type of polymeric layer, which is able to create a mooring in the mineral fibres. Preferably, the primer layer is a layer of acrylic paint or cured polyvinyl acetate, said primer should preferably having an average thickness corresponding to up to 250 g/m-, preferably corresponding to 20-150 g/m-.

The acrylic paint may be acrylic paints delivered by iYGEA under the numbers Hygxa 7437-3252 and Hygæa 7429-

4040. The acrylic paints may be used alone or in combination with each other.

The mineral fibre insulating board according to the invention should preferably partly be covered with adhesive, and the adhesive should preferably cover at least 40 ^-=, more preferably at least 50 3-, and even more preferably at least 60 % of the face surface. The mineral fibre insulating board should preferably comprise an intermediate layer of the primer. The intermediate layer of primer preferably covers substantially the whole face surface.

The adhesive should preferably be placed in a pattern as described above.

Furthermore, the invention relates to a covering material in the form of a foil comprising a back surface and a front surface opposite to said face surface, said face surface being totally or partly covered with a layer of an adhesive as described above. Preferably, the covering material is a foil based on PVC, CPE, TPO, or EDPM.

Furthermore, the invention relates to a covering material coated with adhesive as described above in combination with a mineral fibre insulating board totally or partly coated with a primer as described above.

The present invention is particularly useful for covering roof structures, but may as described also be use for covering walls and floors.

EXAMPLE 1 A two-layer mineral fibre board consisting of an insulating layer having a height of 200 mm and a density

of 100 kg/m and a surface layer of 20 mm and a density of 180 kg/m are applied with a PVAc primer. The PVAc is applied via spray nozzles in an amount of 125 g/m-onto the entire surface, dry matter content 50%. The water content in the PVAc is subsequently evaporated by means of infrared heating elements.

After drying of the PVAc, a silicone adhesive is applied in strips with a width of 10 cm and with a spacing of 10 cm in an amount of 50 g/m-. The adhesive contains 70 % of silicone and 30-of xylene. The content of solvent xylene is evaporated by means of infrared heat radiation.

A delamination strength of 6 KPa is obtained. A peel strength of 35 N/50mm is obtained, with a pull speed of 50 mm/min.

A PET protective foil is subsequently applied which when purchased has been applied with a release agent, which ensures a non-stick effect. It is the object of the protective foil to protect the adhesive against soiling and drying-out, and to ease handling during the subsequent mounting on roof.

Process on roof: The roofing boards are adhered manually onto the roof in a manner known per se using a PU-adhesive, and roofing foil of the type PVC is positioned in relation to the roof edge.

When this has been done the protective foil is removed roofing board by roofing board, simultaneously with the roofing foil being unrolled. The unrolling is performed with overlapping to the preceding roofing foil. The

adhesive starts by reacting with the roofing foil, so any corrections direction-wise must be made at once.

When the roofing foil has been unrolled, the roofing foil is rolled e. g. with a broom or brush. This ensures that the roofing foil everywhere gets into contact with the adhesive, and that any thickness tolerances on the roofing boards are evened out.

Finally, the overlappings are welded together in a manner known per se either with a traditional hot-air welder or a gas burner, depending on which roofing foil is used.

Hereafter the roof is finished.

EXAMPLE 2 A two-layer mineral fibre board consisting of an insulating layer having a height of 100 mm with a density of 120 kg/m'and a surface layer of 20 mm with a density of 180 : g/m' and a surface of 5 mm with a density of 500 kg/m3 are applied with two types of Hygæa primer. The first primer Hygasa 7437-3252 is applied with a brush in an amount of 60 g/m-and dried. Thereafter Hygæa 7429- 4040 is applied with a brush in an amount of 30 g/m-and dried.

After drying of the primers, a release tape with a nitrile adhesive is placed upon the surface that turns towards the insulation with the primer. To obtain good contact between adhesive and insulation the tape is pressed towards the surface with a broom or brush.

A peel strength of 35 N/50mm is obtained, with a pull speed of 50 mm/min.

A PET protective foil is subsequently applied which when purchased has been applied with a release agent, which ensures a non-stick effect. It is the object of the protective foil to protect the adhesive against soiling and drying-out, and to ease handling during the subsequent mounting on roof.

Hereafter the roofing boards are applied as described in example 1"Process on roof".