COMPOSITE PANEL AND METHOD FOR ITS FORMATION

Abstract: A composite panel characterised by comprising: a central layer (2) of calcium silicate; two sodium silicate films (4) coating said central layer; two resin layers (6, 8, 14) covering said calcium silicate layer coated by said films; two outer layers (10, 12, 16) of flexible material having high mechanical strength.

Description: COMPOSITE PANEL AND METHOD FOR ITS FORMATION This invention relates to a composite panel and a method for its formation. An object of the invention is to provide a composite panel, in particular for use as a ship-fitting bulkhead offering considerable noise abatement, mechanical strength before and after the ageing cycle, fire-resistance, weather resistance, salt fog and mildew resistance, resistance to natural ship vibration and resistance to temperature change. A further object of the invention is to provide a panel of low cost. A further object of the invention is to provide a panel which can be easily machined, is robust and durable, and is of pleasant outer appearance. A further object of the invention is to provide a simple, low-cost method for forming the panel. These and further objects which will be apparent from the ensuing description are attained according to the invention by a panel as claimed in claim 1. Some preferred embodiments of the invention are described in detail hereinafter with reference to the accompanying drawings, on which: Figure 1 is an exploded view of the components of a first embodiment of the panel, Figure 2 shows a second embodiment thereof, Figure 3 shows a third embodiment thereof, Figure 4 shows a fourth embodiment thereof, Figure 5 shows a fifth embodiment thereof, and Figure 6 shows an apparatus for forming the panel of the invention. As can be seen form the figures, the composite of the invention comprises an intermediate first layer 2 of porous calcium silicate material (insulating material) produced in an autoclave from siliceous sand, slaked iime and a small percentage of cellulose reinforcement fibres enabling a compact layer to be obtained which is incombustible (class 0), fir-resistant (REI 180) and non-toxic, but extremely fragile. This material preferably has a density of 250 kg/m 3 , a thickness of 22 mm and a weight of 5.5 kg/m 2 . Said first layer 2 is covered with two films 4 of sodium silicate acting as a hardener, to counteract the surface friability of the calcium silicate. To the outside of one of the sodium silicate films 4 there is applied a layer 6 of viscoelastic two-component poiyurethane resin having a low flame propagation propensity. To the outside of the other sodium silicate film 4 there is applied a layer 8 of two-component poiyurethane resin having a low flame propagation propensity. An aluminium layer 10 preferably of 0.6 mm thickness is applied to the outside of the viscoelastic resin layer 6, and a layer 12 of self-extinguishing biaxial glass fibre matting with fibres crossing at 90° is applied to the outside of the resin layer 8. A further layer of two-component poiyurethane resin is applied to the outside of said layer 12. From the aforegoing it is apparent that the panel of the invention attains the stated objects, in that: - it enables good noise abatement to be achieved because of the presence of the viscoelastic two-component poiyurethane resin layer 6, - it presents good fire-resistance by virtue of the perfect synergy of the different panel constituent materials and the good fire-resistance of the calcium layer 2, - it presents good water resistance because of the presence of the aluminium layer 10 and the biaxial glass fibre matting layer 12 covering the extremely porous calcium silicate layer 2, - it presents good resistance to salt fog, mildew, and natural ship vibration, with consequent good durability, by virtue of the perfect synergy of the main inert constituent materials of the panel, - it is of low weight because of the use of very light materials (aluminium and silicates), - it provides good machinability (in particular the formation of very rigid continuous angles) because of its good mechanical strength, - it is of pleasant outer appearance. The method for forming the panel of the invention comprises applying a layer 6 of viscoelastic two-component poiyurethane resin to an aluminium sheet 10 unwound from a reel 18, then applying to said layer a plurality of side-by-side plates 20 of calcium silicate covered on both their surfaces with a film of sodium silicate. To the free surface of said plates there is then applied a two-component poiyurethane layer 8 followed by a layer 12 of biaxial glass fibre matting unwound from a reel 22. A further component two-component poiyurethane layer 8 is then applied to the outside of said layer 12. The entire assembly obtained in this manner is subjected to the action of a dynamic press 24, at the exit of which the panel is cut by a cutter 26 to the desired length. In the embodiment shown in Figure 2, the composition of the central layer remains unchanged, whereas in the outer part of the panel the two- component poiyurethane resin layers 8 are replaced by viscoelastic two- component poiyurethane resin layers 8. In the embodiment shown in Figure 3, the panel has the same composition as the panel shown in Figure 1 , but with the central layer of this latter now replaced by two smaller-thickness calcium silicate layers 2, between which one viscoelastic two-component poiyurethane resin layer 6 and two sodium silicate layers 4 are interposed. The panel shown in Figure 4 has substantially the same components as the panel shown in Figure 2, but with the central layer similar to that shown in Figure 3. The panel shown in Figure 5 has a central calcium silicate layer 2 interposed between two sodium silicate layers 4, external to which there are two layers 14 of two-component unsaturated polyester resin with a low flame propagation propensity, to these two latter layers there being applied a layer 12 of seif-extinguishing biaxial glass fibre matting. To the outside of said biaxial glass fibre matting layers 12 there is applied a further layer 14 of two-component unsaturated polyester resin followed, on that latter layer which faces inwards, by a layer 16 of plastic laminate preferably of 0.6 mm.

Claims: C L A I M S 1. A composite panel characterised by comprising: - a central layer (2) of calcium silicate, - two sodium silicate films (4) coating said central layer, - two resin layers (6,8, 14) covering said calcium silicate layer coated by said films, - two outer layers (10,12,16) of flexible material having high mechanical strength. 2. A panel as claimed in claim 1 , characterised in that at least one resin layer consists of a viscoelastic two-component poiyurethane resin (6) having a low flame propagation propensity. 3. A panel as claimed in claim, characterised in that at least one resin layer consists of a two-component poiyurethane resin (8) having a low flame propagation propensity. 4. A panel as claimed in claim 1 , characterised in that at least one resin layer consists of an unsaturated polyester resin (14) having a low flame propagation propensity. 5. A panel as claimed in claim 1 , characterised in that at least one outer layer of flexible material consists of a self-extinguishing layer (12) of biaxial glass fibre matting with fibres crossing at 90°. 6. A panel as claimed in claim 1 , characterised in that at least one outer layer of flexible material consists of aluminium (10). 7. A panel as claimed in claim 1 , characterised in that at least one outer layer of flexible material consists of plastic laminate (16). 8. A panel as claimed in claim 1 , characterised in that the central layer consists of two calcium silicate layers between which one viscoelastic two- component poiyurethane resin layer (6) and two sodium silicate layers (4) are interposed. 9. A panel as claimed in claim 1 , characterised in that at least one outer layer of flexible material consists of a layer of biaxial glass fibre matting with fibres crossing at 90°. 10. A method for the continuous formation of panels claimed in claims 1 to 9, characterised by comprising the following steps: - applying a resin layer to a continuous layer of high-strength flexible material, - applying to said resin layer a plurality of side-by-side calcium silicate plates covered on both their surfaces with a sodium silicate film, - applying a further resin layer to said plates, - applying a further layer of high-strength flexible material, - subjecting the assembly obtained in this manner to the action of a press, - cutting the panel to the required length.

Inventors: DOIMO EROS, DOIMO, EROS
Applicants: DOIMO EROS, FREZZA S R L, DOIMO, EROS, FREZZA S.R.L.
Application year: 2000
Main classification: B32B27
IPC codes: B32B27, C09K21