Patent Description:
From the point of view of energy saving, in the building industry the need is increasingly felt to thermally insulate buildings in order to promote a good diffusion of heat inside the premises and, at the same time, avoid its dispersion to the outside. To this end, multilayer insulation panels are widely used in buildings, for example to ensure the thermal insulation of walls, floors and roofs. Such insulation panels generally comprise an insulation layer, for example made in polyurethane foam, sandwiched between two respective backing layers suitable for covering the insulation layer. Said backing layers perform a dual role: on the one hand they limit the expansion of the polyurethane foam, and on the other provide said panels with a predefined shape and thickness, at the same time ensuring dimensional stability to the panels.

For such applications, rigid polyurethane foam has recently proven highly successful given that, having a mean coefficient of thermal conductivity λ [W m -<NUM> K -<NUM> ] lower than other commercial insulating materials, it makes it possible to obtain a good thermal insulation using panels of lesser thickness. Consequently, for the same insulation effects, the insulation panels for buildings using polyurethane foam have reduced volumes and weights compared to insulation panels made with other insulation materials.

As is known, the reduced thermal conductivity of polyurethane foam and similar synthetic foam products (polystyrene, styrene) is due to their cellular structure: in these foams about <NUM>% -<NUM>% in volume is composed of the polymer and the remaining <NUM>% -<NUM>% of a gaseous phase of expanding agents enclosed in closed cells. The small amount of the polymer and the gaseous phase limit the thermal conduction, while the limited size of the closed cells limits the thermal convection between the gas and the inner surface of such cells.

The phenomenon that most prejudices the performance of these cellular structures is the partial diffusion of the gaseous phase to the outside of the panel. Such diffusion needs to be minimised as much as possible to maintain the insulating properties of the panel substantially unchanged over time.

Insulating panels for buildings are known of in which the phenomenon of diffusion of the gaseous phase is limited by the application on both sides of the panel of a coating impermeable to diffusion, i.e. a gas-tight coating. For example, the insulating panels containing polyurethanes (PUR) or polyisocyanurate (PIR) with a gas-tight coating currently on the market are made using a metal coating applied to the faces of the panel, in particular a single layer or sheet of aluminium or a sheet backed with plastic films, paper or fibreglass.

For such insulating panels containing insulating foam with cellular structure, the performance in terms of fire resistance of the panel depends mainly on the type of backing layers used. For example, for an insulating panel to be classified B or C fire resistant according to the standard EN <NUM>-<NUM>/<NUM>, i.e. to ensure adequate fire-resistance, even after a thermal shock arising from direct contact with flames during a fire, the backing layers in aluminium are required to be more than <NUM> thick. The disadvantage of panels with aluminium backing layers is mainly related to the cost of manufacturing thick aluminium layers which significantly affects the overall cost of the panel. Document <CIT> discloses a fire retardant insulating construction panel. Document <CIT> discloses a fire protection device comprising a fire protecting foil spaced from the surface of the device being protected, in which the intermediate space between the foil and the protected device surface is foamed.

The main object of the present invention is to devise and making available an insulating panel for buildings comprising a backing layer which, while maintaining substantially unchanged the gas-tight properties of the panel over time, also makes it possible to improve the fire retardant properties of the panel while limiting the production costs thereof.

Such purpose is achieved by a multilayered insulating panel for building constructions according to claim <NUM>.

Preferred embodiments of such insulating panel are described in the dependent claims <NUM>-<NUM>.

The present invention also relates to a method of manufacturing the multilayered insulating panel for buildings according to claim <NUM>.

Further characteristics and advantages of the backing layer for an insulating panel according to the invention will, in any case, be evident from the description given below of its preferred embodiments, made by way of a non-limiting example with reference to the appended drawings, wherein:.

In the aforementioned drawings, elements which are the same or similar will be indicated using the same reference numerals.

With reference to <FIG>, backing layers of a multilayer insulating panel <NUM> for building constructions of the gas-tight type according to the invention are denoted by reference numeral <NUM>.

Such insulating panel <NUM> may be used in the building industry to cover walls (vertical and horizontal), floors and roofs.

Such insulating panel <NUM> comprises a central body <NUM> composed of a cellular structure insulating foam such as polyurethane (PUR) foam or polyisocyanurate (PIR) foam, phenolic or polystyrene foam (PS).

In the embodiment shown in <FIG>, said central body <NUM> of the panel <NUM> is interposed or sandwiched between the two analogous backing layers <NUM> of the invention. In an alternative embodiment the central body <NUM> of the panel may be placed between a backing layer <NUM> and a finishing layer, having gas-tight properties, different from the aforesaid backing layer as will be explained in more detail below.

Such backing layers <NUM> are configured to limit the expansion of the polyurethane (or polyisocyanurate) foam during the manufacturing stages of the panels <NUM>. Moreover, the backing layers <NUM> are suitable to give the panels <NUM> a predetermined shape and a thickness while ensuring the dimensional stability of said panels.

Each of the aforesaid backing layers <NUM> comprises a gas-tight reinforcement layer <NUM> comprising a first surface F1 and an opposite second surface F2.

In one embodiment, the gas-tight reinforcement layer <NUM> of the backing <NUM> is composed of a layer of metal 1A, for example of aluminium. In an example which does not form part of the invention such gas-tight reinforcement layer <NUM> takes the form of a plastic film or a metallised plastic film.

In addition, the backing layer <NUM> comprises a fire-resistant layer <NUM> operatively associated to the first surface F1 of the reinforcement layer <NUM>.

In one embodiment, such fire-resistant layer <NUM> is in an expandable material and comprises, in particular, expandable graphite.

In particular, the aforesaid fire-resistant layer <NUM> is made using a mixture comprising for example, the expandable graphite, a plastifying resin and additives. In one embodiment, said mixture of the fire-resistant layer <NUM> comprises:.

In particular, the aforesaid resin is a polymeric dispersion of polymers or copolymers such as for example, acrylics, vinyls, silicone, silanes, siloxanes polyurethanes, to which at least one flame retardant additive is possibly added.

Moreover, the resin is configured to englobe the expandable graphite, in particular creating a film which binds such graphite to the backing <NUM>. In other words, the resin is suitable for plastifying the fire-resistant layer <NUM>, at the same time providing a contribution to the fire resistance of said backing layer <NUM> by means of the further flame retardant additive contained therein.

The expandable graphite of the fire-resistant layer <NUM>, if subjected to temperatures to the order of about <NUM> begins to expand, reaching a maximum expansion when placed in contact with the flames, i.e. at temperatures of about <NUM>-<NUM>. It is to be noted that, in the presence of flames, the graphite can increase its volume from about <NUM> to about <NUM> times. Advantageously, the fire-resistant layer <NUM> with expandable graphite comprised in the backing layer <NUM> of the panel <NUM>, in the presence of flames, is suitable to expand to create a barrier layer which keeps the flames away from the central body <NUM> in polyurethane or, at least, slows down the advance thereof towards said central body inside the panel <NUM>.

With reference to <FIG>, in a second embodiment of the backing layer <NUM> of the invention, the aforementioned reinforcement layer <NUM> comprises a layer of fibrous material <NUM> in addition to a metal layer 1A. It is to be noted that said fibrous layer <NUM> of the reinforcement layer <NUM> is suitable to confer greater mechanical strength to the backing layer <NUM> of the panel <NUM>. Such fibrous layer <NUM> of the reinforcement layer <NUM> is made of a material selected from the group consisting of:.

Again, in a further example, the reinforcement layer <NUM> may be made as a multilayer comprising a metal layer, a plastic film and a fibrous layer in different combinations thereof.

It is to be noted that in the case of a panel <NUM> comprising two backing layers <NUM> having the same stratigraphy, as shown in <FIG>, such panel has fire retardant properties on both sides, in addition to the gas-tight properties. Alternatively, one of the two backing layers may be simply a finishing layer made of a traditional gas-tight material, such as for example, aluminium, multilayer film comprising paper, aluminium and films in plastic materials in various combinations or other metal materials.

One embodiment of the manufacturing method of the backing layer <NUM> (or <NUM>) of the insulating panel <NUM> in which the fire-resistant layer <NUM> is made starting from the mixture comprising the expandable graphite and plastifying resin is described below.

In particular, starting from a reinforcement layer <NUM>, for example of aluminium (with or without the layer of fibrous material <NUM>), the method comprises a first step of spreading on said reinforcement layer the fluid mixture comprising the expandable graphite, the resin and the additives (water, anti-foaming agent, dispersing agent).

Subsequently, the method comprises a drying step, for example in a hot air furnace, of the backing layer <NUM> (or <NUM>). Said drying step permits the drying and plastifying of the resin of the fire resistant layer <NUM>.

It is to be noted that the production line of the backing layer <NUM> (<NUM>) works continuously with a roll to roll system wherein the reinforcement layer <NUM>, comprising for example a sheet of aluminium and a layer of glass fibre, is unwound, the various materials deposited and the backing layer <NUM> (<NUM>) obtained once dry, rewound.

For the manufacture of the insulating panel <NUM>, a first example provides for a step of spraying the polyurethane foam between the two backing layers <NUM> (or <NUM>). Such backing layers are suitable to limit, between the respective second surfaces F2 of the reinforcement layer <NUM>, the expansion of the polyurethane foam forming the central insulating body <NUM>.

A second example of the panel <NUM> provides for gluing the backing layers <NUM> (or <NUM>) onto the opposite surfaces of the pre-formed central insulating body <NUM>. Alternatively, the backing layer <NUM> (or <NUM>) can be laid, in a manner of a sheet, over the insulating layer during the laying of said insulating material, for example on a roof, to form an additional fire resistant layer for said insulating layer. In particular, the backing layer <NUM> (or <NUM>) may also be laid on fibrous, natural or mineral insulating materials.

The backing layers of the insulating panels <NUM> according to the invention have numerous advantages.

Mainly, said backing layers <NUM>, <NUM> give increased fire resistance properties to the insulating panel <NUM>, in particular if said backing layers are applied to both opposite surfaces of the insulating central body <NUM> with insulating foam. In fact, the backing layers <NUM>, <NUM> protect from fire both the gas-tight reinforcement layer <NUM> and the central body <NUM> in insulating foam, preventing or slowing down the advancement of the flames toward the inside of the panel <NUM>.

With the backing layers <NUM>, <NUM> of the invention it is no longer necessary to use thick layers of aluminium to achieve the same performance in terms of fire-resistance of the gas-tight panels of known type. As a result, the total production costs of the gas-tight panel <NUM> using the backing layers <NUM>, <NUM> are significantly reduced.

Furthermore, the gas-tight reinforcement layer <NUM> permits a substantially uniform and homogeneous distribution of the fire-resistant layer <NUM> thereby enhancing the barrier properties to the flames.

In addition, the Applicant has verified that the gas-tight reinforcement layer <NUM> of the backing layer <NUM>, <NUM>, by preventing the diffusion towards the outside of the panel itself of the gases and fumes which may develop in the panel under the backing, creates an additional barrier operating in synergy with the fire-retardant layer <NUM>.

Moreover, when two or more insulating panels <NUM> with the backing layers <NUM>, <NUM> according to the invention are placed adjacent to each other, the use of expandable graphite in the respective fire-resistant layers <NUM> permits, in the case of fire, the protection of the junctions between such adjacent panels. In fact, the expansion of the graphite as the temperature increases makes it possible to seal such junctions.

This solves a particularly relevant drawback of the panels of the prior art comprising gas-tight metal layers. In fact, such known panels currently require sealing-taping operations at the joins to also protect the joins between such adjacent panels from the fire.

Furthermore, the layer of fire retardant coating <NUM> of the backing layers <NUM>, <NUM>, is water resistant and has high resistance to foot traffic and abrasion. In other words, the layer of fire retardant coating <NUM> protects the gas-tight reinforcement layer <NUM>, and in particular during the installation operations of the panels <NUM>, prevents possible damage of the gas-tight aluminium layer which would jeopardise the barrier properties to the diffusion of gas, and, consequently, the thermal insulation properties of the entire panel.

Claim 1:
A multilayered insulating panel (<NUM>) for building constructions comprising a central body (<NUM>), composed of a cellular structure insulating foam, a first backing layer (<NUM>; <NUM>) and a second backing layer, said central body (<NUM>) being interposed between the first backing layer (<NUM>; <NUM>) and the second backing layer;
the second backing layer being analogous to said first backing layer (<NUM>; <NUM>) or
consisting in a finishing layer having gas-tight properties and being different from said first backing layer (<NUM>; <NUM>);
said first backing layer (<NUM>; <NUM>) comprising:
- a reinforcement layer (<NUM>) comprising a first surface (F1) and an opposite second surface (F2), the second surface (F2) of the reinforcement layer (<NUM>) being applied to one of two opposite surfaces of the insulating central body (<NUM>);
- a fire-resistant layer (<NUM>) operatively associated to said first surface (F1) of the reinforcement layer (<NUM>), said fire-resistant layer (<NUM>) being made of an expandable material comprising expandable graphite, wherein
said reinforcement layer (<NUM>) is a gas-tight reinforcement layer (<NUM>) comprising a metal layer (1A) of aluminium.