IT202000013177A1 - SANDWICH PANEL USABLE IN THE FURNISHING SECTOR AND METHOD FOR THE PRODUCTION OF SAID PANEL - Google Patents

Description

DESCRIPTION

Description of the INDUSTRIAL INVENTION entitled:

?Sandwich panel usable in the furniture sector and method for the production of said panel?

Field of application of the invention

The present invention finds application in the furnishing sector and refers, in particular, to a panel in composite material, more precisely ?sandwich?, which can be used in the aforementioned sector for the construction, by way of example, of furniture or partition walls. As known, sandwich panels are panels comprising a central layer, usually defined as a ?core? or ?core?, interposed between at least two surface layers generally more? thin of the central layer and usually defined ?skins? or ?faces?.

The present invention also relates to a method for producing the sandwich panel object of the invention.

Review of known art

Nowadays sandwich panels are widely used as structural elements in many technical fields. Among the most widespread sandwich panels are those comprising a core made up of an aluminum or Kevlar honeycomb sandwiched between two aluminum skins glued to said core using polyvinyl acetate (also known as ?vinyl glue?) or a resin melamine. Such panels are very performing in terms of rigidity, stability? dimensional and flatness, but are just as heavy as solid wood or ?medium-density fibreboard? (a derivative of wood also known by the acronym ?MDF?). Unfortunately, the weight of these panels constitutes a significant disincentive to their use in the furniture sector.

An alternative to the sandwich panels described above? made up of panels comprising a polyvinyl chloride foam core (also known by the acronym ?PVC?) or polyethylene terephthalate (also known by the acronym ?PET?) interposed between two marine plywood skins glued to said core by means of polyvinyl acetate or a melamine resin. Such panels are more? light compared to those of the previous type but have properties? less appreciable mechanics in the furniture sector.

In order to improve the aforementioned properties? In technical sectors such as aerospace and biomedical, panels have been developed comprising a core made up of polyvinyl chloride foam placed between two skins in carbon fiber laminate glued to said core using an epoxy resin. Incidentally, with the expression ?laminate carbon fiber? basically means a sheet obtained by pressing one or more? layers of woven carbon fibers impregnated with epoxy resin.

Sandwich panels of the latter type are light and extremely performing in terms of flatness and non-deformability. Nonetheless, if subjected to squaring and edging operations (operations generally performed on panels intended for the furniture sector), these panels are not able to withstand, without damaging themselves, the pressures and crushing impressed by machinery such as squaring and edging machines . The above excludes the use of sandwich panels of the latter type in the furniture sector.

Incidentally, with the term ?squadratura? it means a precision cutting operation of a panel carried out in order to give it a precise polygonal shape. The squaring operation of a panel is performed using a machine called a ?squaring machine?. The squaring operation, cos? like squaring machines, they are substantially known. We therefore do not dwell on providing further details.

Incidentally again, with the term ?edging? it means an operation consisting in applying a generally wooden, plastic or metallic border to a panel along the edges of the same. The edgebanding operation of a panel is performed using a machine known as an "edging machine". The edging operation, cos? like edge banders, they are substantially known. We therefore do not dwell on providing further details.

Purposes of the invention

Purpose of the present invention? that of overcoming the aforementioned drawbacks by indicating a sandwich panel which, in addition to possessing the characteristics of lightness, flatness? and non-deformability typical of the panels described above comprising a polymeric foam and carbon fiber laminates, can undergo squaring and edging operations during its production phase without this? preclude the use of said panels in the furniture sector. Another purpose of the present invention? to indicate a method for the production of a sandwich panel that includes the operations of squaring and edging without that there? precludes the use in the furnishing sector of a panel obtained by implementing said method.

Summary and advantages of the invention

Object of the present invention ? a panel in composite material, sandwich, comprising:

? a central layer acting as a core of said panel and including an expanded foam made of at least one thermoplastic polymeric material, said expanded foam having a density? between 50 kg/m<3 > and 150 kg/m<3>, and preferably 60 kg/m<3>.

The thermoplastic polymer material in which? made the aforementioned foam? preferably polyvinyl chloride or polyethylene terephthalate;

? a first and a second surface layer acting as first skins of said panel and each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin, said first surface layer being superimposed on said central layer and being connected to this lastly by means of a glue including epoxy resin (which is therefore interposed between said central layer and said first surface layer),

said second surface layer being superimposed on said central layer on the opposite side with respect to said first surface layer so that? said central layer is interposed between said first and second surface layers, said second surface layer being connected to said central layer by means of an adhesive including epoxy resin (which is therefore interposed between said central layer and said second surface layer),

wherein, according to the invention, said panel further comprises:

? at least one edge (preferably of wood, plastic or metal) connected to said central layer along its margins in such a way that said edge covers faces of said central layer not covered by said first and second surface layers;

? a third and a fourth surface layer acting as second skins of said panel and each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin, said third surface layer being superimposed on said first surface layer on the opposite side with respect to to said central layer so that? said first surface layer is interposed between said central layer and said third surface layer,

said third surface layer being connected to said first surface layer by means of an adhesive including epoxy resin (which is therefore interposed between said first and third surface layers),

said fourth surface layer being superimposed on said second surface layer on the opposite side with respect to said central layer so that? said second surface layer is interposed between said central layer and said fourth surface layer,

said fourth surface layer being connected to said second surface layer by means of an adhesive including epoxy resin (which is therefore interposed between said second and fourth surface layers).

The panel object of invention? extremely light and has excellent properties? structural in terms of stability? dimensional, planarity?, non-deformability? and bending strength. Said panel ? furthermore advantageously edged. There? ensures that the panel object of the invention is suitable for use in the furniture sector. How will it be? illustrated in the following of the present description, the squaring and the edging take place after the application of the first skins on the core and before the application of the second skins on the first skins.

Other innovative characteristics of the present invention are illustrated in the following description and referred to in the dependent claims.

According to one aspect of the invention, each of said first, second, third and fourth surface layers comprises a laminate including said fabric, in each of said first and second surface layers, said fabric being biaxial or multiaxial.

Advantageously, according to this aspect of the invention, the panel is even more dimensionally stable.

According to another aspect of the invention, in each of said first, second, third and fourth surface layers, the carbon fibers are present in a weight percentage ranging from 25% to 55%, and preferably equal to 30%. According to another aspect of the invention, said panel further comprises: ? a fifth and sixth surface layer, each of which comprising a ceramicised acrylic paint (including acrylic resin with ceramic nanoparticles added) or a polyurethane paint or a polyester paint,

said fifth surface layer being superimposed on said third surface layer on the opposite side with respect to said first surface layer so that? said third surface layer is interposed between said first and fifth surface layer,

said fifth surface layer being connected to said third surface layer by means of a polyester primer (which is therefore interposed between said third and fifth peripheral layers),

said sixth surface layer being superimposed on said fourth surface layer on the opposite side with respect to said second surface layer so that? said fourth surface layer is interposed between said second and sixth surface layers,

said sixth surface layer being connected to said fourth surface layer by means of a polyester primer (which is therefore interposed between said fourth and sixth surface layers).

Advantageously, the varnishing of the second skins according to this aspect of the invention gives them brightness and a high resistance to scratches and abrasions. There? makes the panel object of? invention even more? suitable for use in the furniture sector. Furthermore, the polyester base saturates and fills the porosity? present on the external surface of the second skins. According to another aspect of the invention, called polyester primer, so such as said polyester paint if included in said fifth and sixth surface layers, comprises:

? direct gloss unsaturated polyester;

? a hardener of said direct gloss unsaturated polyester,

the weight ratio between said unsaturated direct gloss polyester and said hardener being between 100:1 and 100:3, and ? preferably 100:2.

According to another aspect of the invention:

? if said fifth and sixth surface layers include said ceramic-coated acrylic varnish, the latter includes:

? a base component comprising acrylic resin additived with ceramic nanoparticles;

? a hardener of said acrylic resin,

the weight ratio between said base component and said hardener of the acrylic resin being between 100:40 and 100:60, and ? preferably 100:50;

? if said fifth and sixth surface layers include said polyurethane varnish, the latter includes:

? a base component comprising polyurethane resin;

? a hardener of said polyurethane resin,

the weight ratio between said base component of the polyurethane paint and said hardener of the polyurethane resin being between 100:40 and 100:60, and ? preferably 100:50.

According to another aspect of the invention, said panel further comprises: ? a seventh and an eighth surface layer, each of which results from the drying of liquid glass (also called ?soluble glass?, i.e. an amorphous material that has the appearance of a transparent glass and includes alkali metal silicates) with the addition of ceramic nanoparticles,

said seventh surface layer being superimposed on said fifth surface layer on the opposite side with respect to said third surface layer so that? said fifth surface layer is interposed between said third and seventh surface layer,

said eighth surface layer being superimposed on said sixth surface layer on the opposite side with respect to said fourth surface layer so that? said sixth surface layer is interposed between said fourth and eighth surface layer.

Advantageously, the application of a layer of liquid glass on the ceramic or polyurethane or polyester acrylic paint considerably increases the surface resistance of the latter (ie the resistance to scratches and abrasions). In addition to this, the liquid glass advantageously protects the transparent type painting on which it is placed. applied, from yellowing phenomena due to the action of ultraviolet rays.

Another object of invention? a method for manufacturing a sandwich composite panel comprising the following steps:

a) accomplish;

? a plate acting as the core of said panel and comprising expanded foam made of at least one thermoplastic polymeric material,

said expanded foam having a density? between 50 kg/m<3 > and 150 kg/m<3>, and preferably 60 kg/m<3>.

The thermoplastic polymer material in which? made the aforementioned foam? preferably polyvinyl chloride or polyethylene terephthalate;

? a first and a second skin of said panel each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin;

b) superimposing said first skin on said core by connecting them to each other by means of an adhesive including epoxy resin (which is therefore interposed between said core and said first skin);

c) superimposing said second skin on said core on the opposite side with respect to said first skin so that? said core is interposed between said first and second skin

connecting said second skin to said core by means of an adhesive including epoxy resin (which is therefore interposed between said core and said second skin);

wherein, according to the invention, said method comprises the following further steps: d) pressing said first and second skins, towards each other, against said core for at least 12 hours (preferably for 24 hours) by exerting a pressure of at least 1.5 kg/cm<2 > (preferably at least 2.5 kg/cm<2>),

what? to obtain a semi-finished panel;

e) squaring said semi-finished panel giving the latter a predetermined length and width (by the way defining "thickness" the third dimension of said panel);

f) bordering said squared panel by connecting an edge (preferably wooden, plastic or metallic) to said core along its margins, thus to cover with said border the faces of said core not covered by said first and second skin;

g) making a third and a fourth skin of said panel each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin;

h) superimposing said third skin on said first skin on the opposite side with respect to said core so that? said first skin is interposed between said core and said third skin

connecting said third skin to said first skin by means of an adhesive including epoxy resin (which is therefore interposed between said first and third skins);

i) superimposing said fourth skin on said second skin on the opposite side with respect to said core so that? said second skin is interposed between said core and said fourth skin

connecting said fourth skin to said second skin by means of an adhesive including epoxy resin (which is therefore interposed between said second and fourth skins);

j) pressing said third and fourth skins towards each other, respectively against said first and second skins for at least 12 hours (preferably for 24 hours) by exerting a pressure of at least 1.5 kg/cm<2 > (preferably of at least 2.5 kg/cm<2>).

The method object of the invention advantageously allows to produce a panel that is not only extremely light and with excellent properties? structural in terms of stability? dimensional, planarity?, non-deformability? and resistance to bending, but also squared and edged in the desired way (after the application of the first skins on the core and before the application of the second skins on the first skins) so that? said panel is suitable for use in the furniture sector. In other words, in the method which is the object of the invention, steps e) and f) are essential for the purpose of using a panel produced by implementing said method in the furnishing sector.

Other innovative characteristics of the present method invention are illustrated in the following description and referred to in the dependent claims. According to one aspect of the method invention, each of said first, second, third and fourth skins comprises a laminate including said fabric, in each of said first and second skins, said fabric being biaxial or multiaxial.

According to another aspect of the method invention, in each of said first, second, third and fourth skins, the carbon fibers are present in a weight percentage ranging from 25% to 55%, and preferably equal to 30% .

According to another aspect of the method invention, said method, after step j), comprises the following further steps:

k) applying a layer comprising a polyester primer to each of said third and fourth skins,

one of said layers comprising a polyester primer being applied to said third skin on the opposite side with respect to said first skin so that? said third skin is interposed between said first skin and said layer comprising a polyester base,

the other of said layers comprising a polyester primer being applied to said fourth skin on the opposite side with respect to said second skin so that? said fourth skin is interposed between said second skin and said other layer comprising a polyester base;

l) applying on each of said layers comprising a polyester primer a layer comprising a ceramicised acrylic paint (including acrylic resin with ceramic nanoparticles additive) or a polyurethane paint or a polyester paint,

each of said layers comprising a varnish being applied to one of said layers comprising a polyester base on the opposite side with respect to said skin to which said layer comprising a polyester base? been applied so that? each of said layers comprising a polyester base is interposed between one of said layers comprising a paint and said leather to which said layer comprising a polyester base? been applied.

According to another aspect of the method invention, called polyester primer, so? such as said polyester paint when included in said layers comprising a paint, comprises:

? direct gloss unsaturated polyester;

? a hardener of said direct gloss unsaturated polyester,

the weight ratio between said unsaturated direct gloss polyester and said hardener being between 100:1 and 100:3, and ? preferably 100:2.

According to another aspect of the method invention:

? if said layers comprising a varnish include said ceramicised acrylic varnish, the latter comprises:

? a base component including acrylic resin additived with ceramic nanoparticles;

? a hardener of said acrylic resin,

the weight ratio between said base component and said hardener of the acrylic resin being between 100:40 and 100:60, and ? preferably 100:50;

? if said layers comprising a varnish include said polyurethane varnish, the latter comprises:

? a base component including polyurethane resin;

? a hardener of said polyurethane resin,

the weight ratio between said base component of the polyurethane paint and said hardener of the polyurethane resin being between 100:40 and 100:60, and ? preferably 100:50.

According to another aspect of the method invention, said method, after step l), comprises the following further step:

m) applying to each of said layers comprising said ceramicised acrylic paint or said polyurethane paint or said polyester paint a layer comprising liquid glass with ceramic nanoparticles added,

each of said layers comprising liquid glass being applied to one of said layers comprising a varnish on the opposite side with respect to said layer comprising a polyester primer to which said layer comprising a varnish ? been applied so that? each of said layers comprising a varnish is interposed between one of said layers comprising liquid glass and said layer comprising a polyester primer wherein said layer comprising a varnish ? been applied.

Brief description of the figures

Further objects and advantages of the present invention will become clear from the following detailed description of embodiments of the same and from the annexed drawings, given for purely explanatory and non-limiting purposes, in which:

? Figure 1 is an exploded view of a panel according to the present invention; ? Figure 2 is an exploded view of a first variant of the panel of Figure 1; ? Figure 3 is an exploded view of a variant of the panel of Figure 2;

? figure 4 is an exploded view of a second variant of the panel of figure 1.

Detailed description of some preferred embodiments of the invention

In the continuation of this description, a figure may also be illustrated with reference to elements not expressly indicated in that figure but in other figures. The scale and proportions of the various elements depicted do not necessarily correspond to the real ones.

Figure 1 shows a panel 1, object of the invention, made of composite material and, in particular, of the "sandwich" type. Panel 1 comprises a central layer 2 acting as a ?core? and including a foamed foam made of at least one thermoplastic polymeric material. Pi? precisely, the soul 2 ? preferably consisting of said expanded foam. The latter has a density? between 50 kg/m<3 > and 150 kg/m<3>, and preferably 60 kg/m<3>. The thermoplastic polymer material in which? made the aforementioned foam? preferably polyvinyl chloride or polyethylene terephthalate. For illustrative purposes only, the soul 2 ? rectangular parallelepiped shape, with the length and width prevailing over the thickness.

The panel 1 further comprises a first and a second surface layer (ie peripheral) 3 and 4 acting as skins and each of which including a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin. Pi? precisely, each of the skins 3 and 4 preferably comprises a laminate in a single preferably biaxial or multiaxial carbon fiber fabric and impregnated with an epoxy laminating resin. Said single carbon fiber fabric has a basis weight preferably equal to 300 g/m<2>. In each of the skins 3 and 4 the carbon fibers are present in a percentage by weight preferably between 25% and 55%, and more? preferably equal to 30%. Skin 3 ? superimposed on the core 2 in correspondence with the face of the latter facing upwards in figure 1 and ? preferably matching with said face. Skin 4? superimposed on the core 2 on the opposite side with respect to the skin 3. The skin 4 ? that is? superimposed on the core 2 in correspondence with the face of the latter facing downwards in figure 1 and, like the skin 3, ? preferably matching with said face. In the light of what has been said, the soul 2 ? placed between the skins 3 and 4. Each of said skins 3 and 4 ? connected to the core 2 by means of an adhesive including epoxy resin. Pi? precisely, said glue preferably comprises epoxy resin for lamination obtained by mixing a base component with the relative hardener in a weight ratio preferably between 100:25 and 100:45, and more? preferably equal to 100:35. Incidentally, since the skins 3 and 4 are connected to the core 2 by means of the aforementioned glue, the latter is placed between the core 2 and each of the skins 3 and 4.

The panel 1 comprises a third and a fourth surface layer (i.e. peripheral) 5 and 6 acting as second skins and each of which, like the skins 3 and 4, including a fabric at least partially made of carbon fibers and at least partially impregnated with resin epoxy. Pi? precisely, each of the skins 5 and 6 preferably comprises a laminate in a single carbon fiber fabric, preferably of the twill, plain, satin or jacquard type, and impregnated with an epoxy resin for lamination. In each of the skins 5 and 6 the carbon fibers are present in a percentage by weight preferably between 25% and 55%, and more? preferably equal to 30%. Skin 5? superimposed on the skin 3 on the opposite side with respect to the core 2 so that? skin 3 is placed between core 2 and skin 5. Similarly, skin 6 ? superimposed on the skin 4 on the opposite side with respect to the soul 2 so that? the skin 4 is placed between the core 2 and the skin 6. Each of the skins 5 and 6? preferably matching the skin 3 or 4 which ? superimposed. In addition to this, each of the skins 5 and 6 ? connected to the skin 3 or 4 which ? superimposed by means of a glue including epoxy resin. The connection glue of skins 5 and 6 to skins 3 and 4 respectively? preferably the same bonding glue of the hides 3 and 4 to the core 2. Incidentally, since the hides 5 and 6 are respectively connected to the hides 3 and 4 by means of the aforementioned glue, the latter? placed between hides 3 and 5 and hides 4 and 6.

As ? possible to notice in figure 1, the panel 1 ? edged. Does it include what? a preferably wooden, plastic or metallic edge 7 connected to the core 2 along the edges of the same in such a way that the edge 7 covers the faces of the core 2 not covered by the skins 3 and 4. Since the core 2, for the purpose purely illustrative, of rectangular parallelepiped shape, the edge 7 comprises four strips respectively connected to the four lateral faces of the core 2 (that is to the four faces interposed between the two previously mentioned faces respectively facing upwards and downwards in figure 1) and respectively mating with said side faces. Edge 7 ? connected to the core 2 by means of a glue including ethylene vinyl acetate.

By way of non-limiting example, the core 2 has a thickness of 15 mm, each of the skins 3 and 4 has a thickness between 0.9 mm and 1 mm, each of the skins 5 and 6 has a thickness of 0.8 mm and each of the adhesive layers (placed between core 2 and skin 3, between core 2 and skin 4, and between skins 3 and 5 and skins 4 and 6) has a thickness of 0.1 mm.

To produce the panel 1 it is first necessary to make the core 2 (i.e. a plate comprising expanded foam made of at least one thermoplastic polymeric material and having a density between 50 kg/m<3 > and 150 kg/m<3 >) and the four hides 3, 4, 5 and 6. The hide 3 is superimposed on the core 2 in correspondence with the face of the latter facing upwards in figure 1. The hide 4 is superimposed on the core 2 by the opposite side with respect to the skin 3 (ie in correspondence with the face of the core 2 facing downwards in figure 1) so that? the core 2 is interposed between the skins 3 and 4. Each of said skins 3 and 4 is connected to the core 2 by means of the previously mentioned glue including epoxy resin. Pi? precisely, a layer of said glue is interposed between the core 2 and each of the hides 3 and 4 before the latter are superimposed on the core 2. The hides 3 and 4 are then pressed, towards each other, against the core 2 for at least 12 hours (and preferably for 24 hours) exerting a pressure of at least 1.5 kg/cm<2 > (and preferably at least 2.5 kg/cm<2>), so? to obtain a semi-finished panel.

The semi-finished panel is squared by means of a squaring machine in order to give the panel a predetermined length and width, and subsequently edged by means of a beading machine in order to connect the edge 7 to the core 2 along the edges of the same in such a way that the edge 7 covers the faces of core 2 not covered by skins 3 and 4.

The skin 5 is superimposed on the skin 3 on the opposite side with respect to the core 2 so that? the skin 3 is placed between the core 2 and the skin 5. Similarly, the skin 6 is superimposed on the skin 4 on the opposite side with respect to the core 2 so that? the skin 4 is interposed between the core 2 and the skin 6. Each of the skins 5 and 6 is connected to the skin 3 or 4 which ? superimposed by means of the aforementioned glue including epoxy resin. Pi? precisely, a layer of said glue is interposed between the hides 3 and 5 and the hides 4 and 6 before the hides 5 and 6 are respectively superimposed on the hides 3 and 4. The hides 5 and 6 are then pressed, one towards the other, respectively against the skins 3 and 4 for at least 12 hours (and preferably for 24 hours) exerting a pressure of at least 1.5 kg/cm<2 > (and preferably at least 2.5 kg/cm<2> ), what? to obtain panel 1.

Advantageously, the squaring and edging operations are carried out after the application of the hides 3 and 4 and before the application of the hides 5 and 6. makes it possible to use panel 1 in the furniture sector.

Figure 2 shows a panel 10 which differs from panel 1 in that it comprises a fifth and a sixth surface layer (i.e. peripheral 11 and 12) each of which comprising a ceramicized acrylic varnish (including acrylic resin additived with ceramic nanoparticles) or a polyurethane varnish. Pi? precisely, each of the layers 11 and 12 ? preferably exclusively composed of a ceramized acrylic varnish or a polyurethane varnish. Layer 11? superimposed on the skin 5 on the opposite side with respect to the skin 3 so that? the skin 5 is interposed between the skin 3 and the layer 11. Similarly, the layer 12? superimposed on the skin 6 on the opposite side with respect to the skin 4 so that? the skin 6 is interposed between the skin 4 and the layer 12. Each of the layers 11 and 12? preferably matching the skin 5 or 6 which ? superimposed. In addition to this, each of layers 11 and 12 is connected to the skin 5 or 6 which ? superimposed by means of a polyester base. Incidentally, since the layers 11 and 12 are respectively connected to the hides 5 and 6 by means of the aforesaid polyester base, the latter is interposed between skin 5 and layer 11 and between skin 6 and layer 12.

The polyester bottom? preferably obtained by mixing direct gloss unsaturated polyester and a hardener of the latter. The weight ratio between said direct gloss unsaturated polyester and the relative hardener? preferably between 100:1 and 100:3, and ? more preferably 100:2.

The aforementioned ceramized acrylic paint, if present in layers 11 and 12, is preferably obtained by mixing a basic component comprising acrylic resin additived with ceramic nanoparticles, and a hardener of said acrylic resin. The weight ratio between said base component and the hardener of said acrylic resin? preferably between 100:40 and 100:60, and ? more preferably 100:50.

The aforementioned polyurethane paint, if present in layers 11 and 12, is preferably obtained by mixing a basic component comprising polyurethane resin and a hardener of the latter. The weight ratio between said basic component of the polyurethane paint and the hardener of said polyurethane resin? preferably between 100:40 and 100:60, and more? preferably ? by 100:50. In order to produce the panel 10 starting from the panel 1, it is first of all necessary to apply a layer comprising the aforesaid polyester primer to the hides 5 and 6. Pi? precisely, the polyester primer is applied, preferably by spraying, on the leather 5 on the opposite side with respect to the leather 3 (so that the leather 5 is placed between the leather 3 and the polyester primer) and on the leather 6 on the opposite side with respect to the leather 4 (so that the leather 6 is placed between the leather 4 and the polyester base). After the two polyester primers have completely hardened, they are sanded and then painted with the aforementioned ceramicised acrylic varnish and/or the aforementioned polyurethane varnish so as to form the layers 11 and 12. In particular, once the sanding is completed, the layers 11 and 12 are respectively applied to the polyester primers on the opposite side with respect to the hides 5 and 6 to which the polyester primers have been applied so that? the polyester bottoms are interposed between the hides 5 and 6 and the layers 11 and 12.

Figure 3 shows a panel 20 which differs from a panel such as panel 10 in that it comprises a seventh and an eighth surface layer (i.e. peripheral) 21 and 22, each of which results from the drying of liquid glass with the addition of ceramic nanoparticles . Layer 21? superimposed on the layer 11 on the opposite side with respect to the skin 5 so that? layer 11 is interposed between skin 5 and layer 21. Similarly, layer 22 is superimposed on the layer 12 on the opposite side with respect to the skin 6 so that? the layer 12 is interposed between the skin 6 and the layer 22. Each of the layers 21 and 22? preferably matching with the layer 11 or 12 which ? superimposed.

To produce the panel 20 starting from a panel such as the panel 10 it is necessary to apply on the layers 11 and 12 a layer comprising the aforesaid liquid glass with the addition of ceramic nanoparticles and wait for the latter to dry so that it is completely dry. to give rise to layers 21 and 22. Pi? precisely, the liquid glass is applied on the layer 11 on the opposite side with respect to the skin 5 (so that the layer 11 is interposed between the skin 5 and the liquid glass) and on the layer 12 on the opposite side with respect to the skin 6 (so that the layer 12 is interposed between the skin 6 and the liquid glass).

Figure 4 shows a panel 30 which differs from the panel 1 in that it comprises a fifth and a sixth surface layer (ie peripheral) 31 and 32, each of which comprising a polyester paint. Pi? precisely, each of the layers 31 and 32 ? preferably exclusively composed of a polyester paint. Layer 31? superimposed on the skin 5 on the opposite side with respect to the skin 3 so that? the skin 5 is interposed between the skin 3 and the layer 31. Similarly, the layer 32 is superimposed on the skin 6 on the opposite side with respect to the skin 4 so that? the skin 6 is interposed between the skin 4 and the layer 32. Each of the layers 31 and 32? preferably matching the skin 5 or 6 which ? superimposed. In addition to this, each of the layers 31 and 32 is connected to the skin 5 or 6 which ? superimposed by means of a polyester base. Incidentally, since the layers 31 and 32 are respectively connected to the hides 5 and 6 by means of the aforesaid polyester base, the latter is interposed between the skin 5 and the layer 31 and between the skin 6 and the layer 32.

Both the polyester paint and the polyester primer are preferably obtained by mixing direct gloss unsaturated polyester and a hardener of the latter. The weight ratio between said direct gloss unsaturated polyester and the relative hardener? preferably between 100:1 and 100:3, and ? more preferably 100:2.

In order to produce the panel 30 starting from the panel 1, it is first of all necessary to apply a layer comprising the aforesaid polyester primer to the hides 5 and 6. Pi? precisely, the polyester primer is applied, preferably by spraying, on the leather 5 on the opposite side with respect to the leather 3 (so that the leather 5 is placed between the leather 3 and the polyester primer) and on the leather 6 on the opposite side with respect to the leather 4 (so that the leather 6 is placed between the leather 4 and the polyester base). After the two polyester primers have gelled (preferably by waiting thirty minutes from their application), they are painted with the aforementioned polyester paint, also preferably applied by spraying, so as to form the layers 31 and 32. In particular , the layers 31 and 32 are respectively applied on the polyester primers on the opposite side with respect to the hides 5 and 6 to which the polyester primers have been applied so that? the polyester primers are interposed between the skins 5 and 6 and the layers 31 and 32. The polyester paint, after being applied, is hardened preferably by placing the panel 30 in a ventilated oven at 30°C. The layers 31 and 32, after hardening, can be smoothed preferably with a belt sander and subsequently polished to a mirror shine, preferably using a roller with fiber bristles which, by rotating, removes any rough edges. present on layers 31 and 32.

Also the panel 30, like the panel 20, could comprise a seventh and an eighth surface layer (ie peripheral) each of which results from the drying of liquid glass with the addition of ceramic nanoparticles. Said seventh layer ? superimposed on the layer 31 on the opposite side with respect to the skin 5 so that? the layer 31 is interposed between the skin 5 and said seventh layer. Similarly, said eighth layer ? superimposed on the layer 32 on the opposite side with respect to the skin 6 so that? the layer 32 is interposed between the skin 6 and said eighth layer. Each of said seventh and eighth layer ? preferably matching with the layer 31 or 32 which ? superimposed.

To add said seventh and eighth layers to a panel such as panel 10, it is necessary to apply on the layers 31 and 32 a layer comprising the aforementioned liquid glass with ceramic nanoparticles added and wait for the latter to dry so that it is completely dry. to give place to said seventh and eighth layer. Pi? precisely, the liquid glass is applied on the layer 31 on the opposite side with respect to the skin 5 (so that the layer 31 is interposed between the skin 5 and the liquid glass) and on the layer 32 on the opposite side with respect to the skin 6 (so that the layer 32 is interposed between the skin 6 and the liquid glass).

Based on the description provided for a preferred embodiment, ? obvious that some changes can be introduced by the technician without the ci? depart from the scope of the invention as defined by the following claims.

Claims (10)

1. Panel (1, 10, 20, 30) in composite material, sandwich, comprising: ? a central layer (2) acting as the core of said panel (1, 10, 20, 30) and including an expanded foam made of at least one thermoplastic polymeric material, said expanded foam having a density? between 50 kg/m<3 > and 150 kg/m<3>; ? a first and a second surface layer (3, 4) respectively acting as first skins of said panel (1, 10, 20, 30) and each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin, said first surface layer (3) being superimposed on said central layer (2) and being connected to the latter by means of an adhesive including epoxy resin, said second surface layer (4) being superimposed on said central layer (2) on the opposite side with respect to said first surface layer (3) so that? said central layer (2) is interposed between said first and second surface layers (3, 4), said second surface layer (4) being connected to said central layer (2) by means of an adhesive including epoxy resin, said panel (1, 10, 20, 30) being characterized in that it also comprises: ? at least one edge (7) connected to said central layer (2) along the edges of the same in such a way that said edge (7) covers faces of said central layer (2) not covered by said first and second surface layers (3, 4); ? a third and fourth surface layer (5, 6) respectively acting as second skins of said panel (1, 10, 20, 30) and each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin, said third surface layer (5) being superimposed on said first surface layer (3) on the opposite side with respect to said central layer (2) so that? said first surface layer (3) is interposed between said central layer (2) and said third surface layer (5), said third surface layer (5) being connected to said first surface layer (3) by means of an adhesive including epoxy resin, said fourth surface layer (6) being superimposed on said second surface layer (4) on the opposite side with respect to said central layer (2) so that? said second surface layer (4) is interposed between said central layer (2) and said fourth surface layer (6), said fourth surface layer (6) being connected to said second surface layer (4) by means of an adhesive including epoxy resin. 2. Panel (1, 10, 20, 30) according to claim 1, characterized in that each of said first, second, third and fourth surface layers (3, 4, 5, 6) comprises a laminate including said fabric, in each of said first and second surface layers (3, 4), said fabric being biaxial or multiaxial. 3. Panel (1, 10, 20, 30) according to one of the preceding claims, characterized in that, in each of said first, second, third and fourth surface layers (3, 4, 5, 6), said carbon fibers they are present in a weight percentage between 25% and 55%. 4. Panel (10, 20, 30) according to one of the preceding claims, characterized in that it also comprises: ? a fifth and a sixth surface layer (11, 12, 31, 32) each of which comprising a ceramicized acrylic paint or a polyurethane paint or a polyester paint, said fifth surface layer (11, 31) being superimposed on said third surface layer (5) on the opposite side with respect to said first surface layer (3) so that? said third surface layer (5) is interposed between said first and fifth surface layer (3, 11, 31), said fifth surface layer (11, 31) being connected to said third surface layer (5) by means of a polyester primer, said sixth surface layer (12, 32) being superimposed on said fourth surface layer (6) on the opposite side with respect to said second surface layer (4) so that? said fourth surface layer (6) is interposed between said second and sixth surface layer (4, 12, 32), said sixth surface layer (12, 32) being connected to said fourth surface layer (6) by means of a polyester primer. 5. Panel (10, 20, 30) according to claim 4, characterized in that said polyester base, so such as said polyester paint if included in said fifth and sixth surface layers (31, 32), comprises: ? direct gloss unsaturated polyester; ? a hardener of said direct gloss unsaturated polyester, the weight ratio between said unsaturated direct gloss polyester and said hardener being between 100:1 and 100:3. 6. Panel (10, 20) according to claim 4 or 5, characterized in that: ? if said fifth and sixth surface layers (11, 12) comprise said ceramic-coated acrylic varnish, the latter includes: ? a base component comprising acrylic resin additived with ceramic nanoparticles; ? a hardener of said acrylic resin, the weight ratio between said base component and said hardener of the acrylic resin being between 100:40 and 100:60; ? if said fifth and sixth surface layers (11, 12) comprise said polyurethane varnish, the latter includes: ? a base component comprising polyurethane resin; ? a hardener of said polyurethane resin, the weight ratio between said base component of the polyurethane paint and said hardener of the polyurethane resin being between 100:40 and 100:60. 7. Panel (20) according to one of claims 4 to 6, characterized in that it also comprises: ? a seventh and an eighth surface layer (21, 22) each of which results from the drying of liquid glass with ceramic nanoparticles as additive, said seventh surface layer (21) being superimposed on said fifth surface layer (11, 31) on the opposite side with respect to to said third surface layer (5) so that? said fifth surface layer (11, 31) is interposed between said third and seventh surface layer (5, 21), said eighth surface layer (22) being superimposed on said sixth surface layer (12, 32) on the opposite side with respect to said fourth surface layer (6) so that? said sixth surface layer (12, 32) is interposed between said fourth and eighth surface layer (6, 22). 8. Method for the production of a panel (1, 10, 20, 30) in composite material, sandwich, comprising the following steps: a) realize: ? a plate (2) acting as the core of said panel (1, 10, 20, 30) and comprising expanded foam made of at least one thermoplastic polymeric material, said expanded foam having a density? between 50 kg/m<3 > and 150 kg/m<3>; ? a first and a second skin (3, 4) of said panel (1, 10, 20, 30) each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin; b) superimposing said first skin (3) on said core (2) connecting them to each other by means of an adhesive including epoxy resin; c) superimposing said second skin (4) on said core (2) on the opposite side with respect to said first skin (3) so that? said core (2) is interposed between said first and second skin (3, 4) connecting said second skin (4) to said core (2) by means of an adhesive including epoxy resin; said method being characterized in that it comprises the following additional steps: d) pressing said first and second skin (3, 4), towards each other, against said core (2) for at least 12 hours by exerting a pressure of at least 1.5 kg/cm<2>, what? to obtain a semi-finished panel; e) squaring said semi-finished panel giving it a predetermined length and width; f) bordering said squared panel by connecting an edge (7) to said core (2) along its margins, thus to cover with said edge (7) the faces of said core (2) not covered by said first and second skin (3, 4); g) making a third and a fourth skin (5, 6) of said panel (1, 10, 20, 30) each of which comprising a fabric at least partially made of carbon fibers and at least partially impregnated with epoxy resin; h) superimposing said third skin (5) on said first skin (3) on the opposite side with respect to said core (2) so that? said first skin (3) is interposed between said core (2) and said third skin (5) connecting said third skin (5) to said first skin (3) by means of a glue including epoxy resin; i) superimposing said fourth skin (6) on said second skin (4) on the opposite side with respect to said core (2) so that? said second skin (4) is interposed between said core (2) and said fourth skin (6) connecting said fourth skin (6) to said second skin (4) by means of a glue including epoxy resin; j) pressing said third and fourth skins (5, 6), towards each other, respectively against said first and second skins (3, 4) for at least 12 hours, exerting a pressure of at least 1.5 kg/cm< 2>. 9. Method according to claim 8, characterized in that it comprises, after step j), the following further steps: k) applying on each of said third and fourth skins (5, 6) a layer comprising a polyester primer, one of said layers comprising a polyester primer being applied to said third skin (5) on the opposite side with respect to said first skin (3) so that? said third skin (5) is interposed between said first skin (3) and said layer comprising a polyester base, the other of said layers comprising a polyester primer being applied to said fourth skin (6) on the opposite side with respect to said second skin (4) so that? said fourth skin (6) is interposed between said second skin (4) and said other layer comprising a polyester base; l) applying on each of said layers comprising a polyester primer a layer (11, 12, 31, 32) comprising a ceramicized acrylic varnish or a polyurethane varnish or a polyester varnish, each of said layers (11, 12, 31, 32) comprising a varnish being applied to one of said layers comprising a polyester base on the opposite side with respect to said skin (5, 6) wherein said layer comprising a polyester base ? been applied so that? each of said layers comprising a polyester base is interposed between one of said layers (11, 12, 31, 32) comprising a paint and said leather (5, 6) to which said layer comprising a polyester base ? been applied. 10. Method according to claim 9, characterized in that it comprises, after step l), the following further step: m) applying on each of said layers (11, 12, 31, 32) comprising said ceramicised acrylic paint or a polyurethane paint or a polyester paint a layer (21, 22) comprising liquid glass with ceramic nanoparticles added, each of said layers (21, 22) comprising liquid glass being applied to one of said layers (11, 12, 31, 32) comprising a paint on the opposite side with respect to said layer comprising a polyester primer to which said layer (11, 12, 31, 32) comprising a varnish ? been applied so that? each of said layers (11, 12, 31, 32) comprising a paint is interposed between one of said layers (21, 22) comprising liquid glass and said layer comprising a polyester primer to which said layer (11, 12, 31, 32) including a varnish ? been applied.