Thermoformable panel for shelves

Abstract

The present invention relates to a thermoformable panel for shelves composed of: at least one core plate having a honeycomb structure composed of a plurality of adjacent cells; a coating layer that includes at least one thermoplastic material coupled to the core plate on at least one face of the core plate. The invention envisions using coating films for the honeycomb core plate that improve adhesion between the material of the honeycomb core plate and the coating films, as well as optional finishing layers overlapped thereon, reducing costs in relation to present honeycomb panels by simplifying manufacturing processes, all while maintaining elevated properties of mechanical strength and low density, and therefore a low weight.

Claims

1. A thermoformable panel comprising: a core plate having a honeycomb structure, which comprises a plurality of adjacent cells arranged with their axes substantially parallel to each other and substantially perpendicular to opposing faces of the core plate; a thermoplastic polymer film bonded to at least one of the faces of the core plate; and a second layer bonded to a face of the thermoplastic polymer film, which is opposed to the core plate; wherein the second layer comprises a nonwoven layer of continuous thermoplastic polymer fibers embedded in a thermoplastic material; wherein at least some of the core plate cells have head edges which at least partially penetrate into the thermoplastic polymer film; wherein at least some of the head edges have enlargements in a direction transverse to the axis of the cells.

2. The panel of claim 1, wherein the thermoplastic polymer film comprises a thermoplastic polyolefin and vegetable and/or mineral fibers.

3. The panel of claim 1, wherein the core plate comprises a plurality of cells peripherally delimited by a shell wall made of natural fibers.

4. The panel of claim 1, wherein thermoplastic material has a lower softening temperature and the continuous thermoplastic polymer fibers have a softening temperature which is higher than the lower softening temperature.

5. The panel of claim 4, wherein the lower softening temperature is about 90 to 120 C. and the continuous thermoplastic polymer fibers have a softening temperature of about 180 to 300 C.

6. The panel of claim 1, wherein the ratio of the continuous thermoplastic polymer fibers to the thermoplastic material is 0.6:1 to 1:1.

7. The panel of claim 1, wherein the thermoplastic polymer film comprises polypropylene filled with wood flour.

8. The panel of claim 1, wherein the non-woven layer has a weight of less than 150 g/m.sup.2 and a thickness of less than 100 m.

9. The panel of claim 1, wherein the thermoplastic polymer film has a thickness of about 0.5 to 3 mm.

10. The panel of claim 1, wherein the continuous thermoplastic polymer fibers comprise polyester fibers and the thermoplastic material comprises polyolefin.

11. The panel of claim 1, wherein the continuous thermoplastic polymer fibers comprise polyethylene terephthalate fibers and the thermoplastic material comprises polypropylene.

12. The panel of claim 1, wherein the thermoplastic polymer film is bonded to a first face of the core plate; and a second thermoplastic polymer film is bonded to an opposing face of the core plate; and a third layer is bonded to a face of the second thermoplastic polymer film, which is opposed to the core plate; wherein the third layer comprises a nonwoven layer of continuous thermoplastic polymer fibers embedded in a thermoplastic material; wherein at least some of the core plate cells have head edges which at least partially penetrate into the second thermoplastic polymer film.

13. The panel of claim 1, wherein the core plate comprises a plurality of cells peripherally delimited by a shell wall made of natural fibers; the thermoplastic polymer film has a thickness of about 0.5 to 3 mm and comprises polypropylene filled with wood flour and/or talc; the non-woven layer has a weight of less than 150 g/m.sup.2 and a thickness of less than 100 m; and the continuous thermoplastic polymer fibers comprise polyethylene terephthalate fibers and the thermoplastic material comprises polypropylene.

14. A method for making the thermoformable panel of claim 1, comprising the following steps: coupling the second layer on a first face of the thermoplastic polymer film; and subsequently coupling a second face of the thermoplastic polymer film on a face of the core plate such that at least some head edges of the core plate cells at least partially penetrate into the thermoplastic polymer film.

15. A thermoformable panel comprising: a core plate having a honeycomb structure, which comprises a plurality of adjacent cells arranged with their axes substantially parallel to each other and substantially perpendicular to opposing faces of the core plate; wherein at least some of the core plate cells have head edges with enlargements in a direction transverse to the axis of the cells; a coating layer bonded to enlarged head edges on one of the core plate faces; wherein the coating layer comprises a nonwoven layer of continuous thermoplastic polymer fibers embedded in a thermoplastic material; and a thermoplastic polymer film bonded to a face of the coating layer, which is opposed to the coating layer face bonded to the core plate; wherein the thermoplastic polymer film comprises thermoplastic polyolefin and vegetable and/or mineral fibers.

16. The panel of claim 15, wherein the thermoplastic polymer film has a thickness of about 0.5 to 3 mm and comprises polypropylene filled with wood flour.

17. The panel of claim 15, wherein the continuous thermoplastic polymer fibers comprise polyester fibers having a softening temperature of about 210 to 250 C. and the thermoplastic material comprises polyolefin having a softening temperature of about 90 to 120 C.

18. The panel of claim 15, wherein the continuous thermoplastic polymer fibers comprise spun bond, non-woven polyethylene terephthalate fibers; the thermoplastic material comprises polypropylene; and the thermoplastic polymer film comprises polypropylene filled with wood flour and/or talc.

19. A thermoformable panel comprising: a core plate having a honeycomb structure, which comprises a plurality of adjacent cells arranged with their axes substantially parallel to each other and substantially perpendicular to opposing faces of the core plate; wherein at least some of the core plate cells have head edges with enlargements in a direction transverse to the axis of the cells; a coating layer bonded to the enlarged head edges on at least one of the core plate faces; wherein the coating layer comprises a nonwoven layer of continuous thermoplastic polymer fibers having a softening temperature of about 180 to 300 C. embedded in a thermoplastic material, which has a softening temperature of about 90 to 120 C.

20. The panel of claim 19, wherein at least some of the head edges with enlargements at least partially penetrate into the coating layer.

21. The panel of claim 19, wherein the thermoplastic material comprises thermoplastic polyolefin; and the nonwoven layer comprises non-woven polyester fibers.

22. The panel of claim 19, wherein the thermoplastic material comprises polypropylene filled with wood flour and/or talc; and the nonwoven layer comprises spun bond, non-woven polyethylene terephthalate fibers.

23. The panel of claim 19, further comprising a finishing layer bonded to an external face of the coating layer on one face of the core plate; wherein the finishing layer comprises polypropylene filled with wood flour and/or talc.

24. The panel of claim 19, wherein the coating comprises a first thermoplastic polymer that is polyvinyl alcohol and a second thermoplastic polymer that is polyamide.

25. The panel of claim 19, wherein the core plate comprises a plurality of cells peripherally delimited by a shell wall made of natural fibers; the non-woven layer has a weight of less than 150 g/m.sup.2 and a thickness of less than 100 m; and the continuous thermoplastic polymer fibers comprise polyethylene terephthalate fibers and the thermoplastic material comprises polypropylene.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) These and other characteristics and advantages of the present invention will be more clear from the following description of some non limitative embodiments shown in the annexed drawings wherein:

(2) FIG. 1 schematically is the structure of a thermoformable panel with a honeycomb core plate according to a first embodiment of the present invention.

(3) FIG. 2 is a variant embodiment of the steps for coupling the coating layers to the faces of the honeycomb core plate.

(4) FIG. 3 schematically is an enlarged section of the thermoformable panel according to this first embodiment.

(5) FIG. 4 schematically is an enlarged section of the panel according a second embodiment of the present invention.

(6) FIG. 5 is, like the previous figures, a combination of the variant embodiments according to FIGS. 3 and 4.

(7) FIGS. 6 to 8 show respectively the steps of applying the coating layers to a honeycomb core plate for making a thermoformable panel according to a fourth embodiment of the present invention.

(8) FIG. 9 schematically shows the step of three-dimensional forming of the thermoformable panel according to the embodiment of the previous FIGS. 3 to 5 by a mould.

DESCRIPTION OF EMBODIMENTS

(9) The description below shows several variant embodiments of the panel according to the present invention. These variants are not to be considered as a limitation, but merely as an illustration of the inventive concept that consists in providing a thermoformable panel with a honeycomb core plate on at least one of its faces a coating layer of plastic material is applied, preferably by lamination or the like such to avoid the different mechanical properties of the honeycomb core plate and of the coating layer or layersdepending on the core plate being riveted on one or two facescausing said layers to separate from each other at least partially at different areas upon bending, due to a relative displacement in a direction parallel to the contact surfaces, thus guaranteeing an optimal stiffness in connection with a limited weight and with the use of less expensive plastic materials.

(10) Although the examples show the presence of coating layers on both the faces of the honeycomb core plate, it is also possible that only one of the faces is coupled to a coating layer or that different coating layers are coupled to the two faces depending on the different embodiments thereof provided in the present description.

(11) FIG. 1 shows a first embodiment wherein a honeycomb core plate 1 is coupled on both the faces with a coating layer 2.

(12) The honeycomb core plate is preferably made of paperboard or similar materials and it is obtained according to known techniques.

(13) Each one of the coating layers 2 is composed of at least two layers, preferably three layers of which at least one layer 202 composed of a non woven of fibers of a first thermoplastic polymer and at least one second layer is composed of a film 201 of a second thermoplastic polymer different than the thermoplastic polymer the fibers of the non woven are made of and having a softening temperature (viscoelastic transition) lower than that of the thermoplastic polymer the fibers of the non woven are made of.

(14) Particularly the second thermoplastic polymer has the lower softening temperature ranging from about 90 C. to 120 C., while the first thermoplastic polymer the fibres of the non woven are made of has a higher softening temperature ranging from about 180 to 300, particularly from about 210 to 250, preferably of about 230.

(15) In FIG. 1 there are provided two films 202 composed of the second thermoplastic polymer the non woven layer with fibres of the first thermoplastic polymer is provided therebetween.

(16) The PET non woven 201 is coated with 2 films that have a double effect and that is to stop the sliding of the fibers when are subjected to a force, an effect that is obtained also by using a mix of two fibers with a different molecular weight and therefore with different softening temperatures, such as described above and also to guarantee the adhesion on the two interfaces (the one with the honeycomb 1 and the above one with the wood-stock plate 4). The PET-based films 202 further guarantee the finished panel, during tests at 80/90 C., to withstand bending in the automotive industry.

(17) According to one embodiment and such as pointed out in FIG. 2, the coupling of the coating layer or layers 2 to the honeycomb core plate 1 occurs for example by hot lamination.

(18) Preferably the coupling occurs in a laminator at a heating temperature ranging from 180 C. to 300 C., particularly from 210 C. to 240 C., preferably at about 230 C.

(19) In these conditions, the polymer with the lower viscoelastic transition temperature penetrates into the interstices of the fibers of the non woven. The latter remain substantially entire since they are composed of a polymer having a higher softening temperature. Thus the fibers are surrounded by the mass of the polymer with a lower softening temperature and are embedded therein forming a reinforcing grid that remains firmly anchored into the material of the polymer having the lower softening temperature upon cooling. Contemporaneously, the pressure exerted in the lamination against the honeycomb core plate 2 is such to generate two possible effects that can be provided both individually and alternatively and in combination with each other.

(20) FIGS. 3 and 5 show such situation.

(21) FIG. 3 schematically shows a section of a panel according to the present invention, wherein in addition to the coating layers there are provided the external finishing layers 4 one on each of the coating layers 2.

(22) Moreover in the case of FIG. 3, the pressure applied for coupling the coating layer to the core plate 1 has partially deformed the head edges of the shell walls 201 of the cells, forming transverse tabs 101 that widen the contact surface between the core plate 2 and the coating layers 1.

(23) Such effect can be promoted by making the head ends of the cells with head edges that are indented and/or not all coplanar with each other.

(24) According to a variant embodiment from FIG. 2, in order to avoid the core plate 2 to be excessively pressed it is possible to provide one or more material inserts, such as wood or the like whose thickness corresponds to the finished thickness of the core plate and that therefore form incompressible stops such to protect the honeycomb core plate against such a pressure that can cause the structure to collapse. Such inserts may be used also for fastening components made of plastic or metal on the external surface of the finished shelf by means of screws.

(25) In a preferred embodiment, the honeycomb core plate is made of paperboard or the like.

(26) It may have a thickness from about one to several centimeters.

(27) As regards the coating layer one embodiment provides the non woven layer to be composed of fibers of polyester, particularly polyethylene terephthalate.

(28) The films 201 of thermoplastic material with a lower softening temperature for example are composed of polyolefin material or other polymers.

(29) The non woven material layer has a weight lower than 150 gr/m.sup.2, preferably lower than 100 gr/m.sup.2, particularly lower than or equal to 90 gr/m.sup.2, and a thickness lower than 100 particularly lower than or equal to 90 m.

(30) The film associated to said non woven has a weight lower than 90 gr/m.sup.2, preferably lower than 70 gr/m.sup.2, particularly lower than or equal to 54 gr/m.sup.2, and a thickness lower than 100 particularly lower than 80 preferably lower than or equal to 60 m.

(31) The honeycomb core plate is made of paperboard or similar materials, while the finishing layer can be made of different materials, and in a preferred variant it is composed of thermoplastic material, particularly polyolefins, especially polypropylene filled with flours of vegetable and/or mineral fibers.

(32) In one embodiment, the finishing layer 4 is applied to the panel, on one of the external faces of one of the coating layers 2 after coupling the coating layers to the honeycomb core plate 1.

(33) The variant of FIG. 4 can be provided at least partially also by using a coating layer such as that described with reference to FIGS. 1 to 3, however it is possible to provide the coating layer to be composed of a plate of thermoplastic material 5, particularly a plate of polyolefins, especially polypropylene filled with flours of vegetable and/or mineral fibers and having a softening temperature preferably higher than 90 C.

(34) To such plate a finishing layer 6 is in turn coupled which is composed of a film or a sheet of thermoplastic fibers having a softening temperature ranging from 180 C. to 300 C., particularly from 210 C. to 240 C., preferably of about 230 C.

(35) Particularly the finishing film 6 is composed of a combination of two thermoplastic polymers each one having a different viscoelastic transition temperature and that is a higher one and a lower one.

(36) Still according to a further characteristic the finishing layer 6 is made according to one or more of the variants described for the coating layer 2 of the previous embodiment according to FIGS. 1 to 3.

(37) The thermoplastic plate composed of polyolefins, preferably polypropylene, filled with flours of vegetable and/or mineral fibers is initially coupled only with the finishing film. The combination of thermoplastic plate 5 and finishing layer 6 then is coupled together to the honeycomb core plate 1 forming its coating layer, the face of the thermoplastic material plate 5 and the face of the core plate 1 being put in contact.

(38) In this case, since the thermoplastic material plate 5 has a low viscoelastic transition temperature, the end portions of the walls 102 delimiting the cells penetrate into the thickness of the thermoplastic material plate 5 partially embedding therein and for a given amount defined by the exerted compression.

(39) This situation is shown in FIG. 4 where said end portions on the head sides of the cells 102 that are denoted by 301 penetrate into the thickness of the material of the thermoplastic material plate 5.

(40) When the finishing layer is made as described with reference to the example in FIGS. 1 to 3, due to the higher viscoelastic transition temperature, said layer remains substantially not penetrable by the end portions 301 of the walls 102 delimiting the cells.

(41) By applying a suitable coupling compression, it is possible to obtain a combination of effects of enlarging the contact surfaces between core plate 1 and coating layer composed of the combination of the layers 5 and 6. In this case as it results from FIG. 5 in addition to the layer 5 penetrated by the end portions 301 of the walls of the cells 102, these end portions also bent at least for a part forming transverse tabs 101.

(42) It has to be noted that in FIGS. 4 and 5 the walls 102 of the cells penetrate through the thickness of the thermoplastic material plate up to the finishing layer 6. However both in the variant of FIG. 4 and in that of FIG. 5, it is possible for some of the cells to have the head edge and/or the associated transverse tab to end at a given distance from the finishing layer 6.

(43) This depends on the initial coplanarity of the head edges of the walls delimiting the cells in the core plate 1 or also on the provision of a preventive treatment of the core plate 1 making the head edges of the walls 102 delimiting the cells as indented, toothed or not coplanar anyway.

(44) With reference to FIGS. 6 to 8, they show the steps for making a thermoformable panel with a honeycomb core according to a further variant of the present invention.

(45) In this case the panel has a honeycomb core plate 1 closed at all the sides, that is also along the perimetral edge by a coating layer 2 which is made according to one of the different variants described.

(46) In this case the thermoformable panel obtained is a kind of blank panel that is an intermediate product that can be stored and used in combination with other material layers, such as for example one or more finishing layers 4, for making three-dimensionally shaped parts, for example by molding.

(47) For producing such panel, it is provided to cut to size the honeycomb core plate 1 and sheets of material intended to form the coating layers according to one or more of the preceding embodiments, the latter having dimensions greater than those of the core plate 1.

(48) A first sheet composed of the material layers according to one of the preceding examples is arranged on a plane and the core plate 1 is placed, centered thereon. On the upper face of the core plate 1 therefore the further sheet or assembly of sheets intended to form the coating layer 2 of the upper face of the core plate 1 is placed.

(49) A frame 7 vertically movable from an idle position to a position where it surrounds all the perimetral edge of the core plate bends, during its translation, the sheet or the assembly of sheets intended to form the upper coating layer 2, this sheet or these sheets also against the perimetral edge and it compresses the remaining perimetral edge of said sheet or said assembly of sheets against the sheet or assembly of sheets intended to form the lower coating layer 2.

(50) This assembly in the condition described and shown in FIG. 7 is placed on the laminator for applying the layers 2 to the honeycomb core plate 1 by lamination. During the lamination also the peripheral parts 302 of the two coating layers 2 that surround the perimetral edge of the core plate 1 are coupled with each other by chemical/physical adhesion projecting beyond said perimetral edge and thus forming a thermoformable panel with the honeycomb core completely coated and with a perimetral frame extending coplanar with one of the two faces.

(51) This embodiment has the advantage that the shape of the core plate 1 remains easily recognizable and therefore the proper positioning of the thermoformable panel in a mold is considerably facilitated for the additional treatment, such as shown in FIG. 9.

(52) This figure shows a mold 8 and a countermold 9 having forming surfaces with a predetermined three-dimensional profile denoted by 108 and 109. As it is possible to see since the shape of the core plate 1 is recognizable it is possible to properly house the thermoformable panel relative to the molds.

(53) In FIG. 9, the forming step provides contemporaneously the step of applying further external finishing layers 4 according to one or more of the embodiment described above.

(54) In this case the fact of extending the two coating layers 2 with respect to the surface of the honeycomb core plate 1, not only helps the side edges thereof to be covered with the coating layer that improves the adhesion of the finishing layer 4 also along the edges and therefore that guarantees a higher mechanical strength, but it helps also to stiffen the two external finishing plates 4 that are sealed with each other along the perimeter of the panel during the thermocompression step. In this case the coating layers 2 and particularly the non woven layers 201 and the films 202 remain compressed along the edges between the two plates, forming a stronger perimetral edge of the panel. Such perimetral edge can be provided with different sectional shapes, for example with a U-shaped cross-section instead of a flat one as in the drawing.