Honeycomb sandwich sheet or panel, based on polypropylene, with a number of central thermoformed films

Abstract

A honeycomb sandwich sheet or panel, based on thermoplastic polypropylene, includes a structure having two flat outer films, at the top and bottom, welded to at least two inner or central thermoformed blister films, repeated in a regular and continuous pattern, wherein the at least two inner thermoformed films are welded to each other.

The invention claimed is: 
     
         1 . An apparatus for producing a sandwich panel,
 the sandwich panel comprising:   two flat outer films made from polypropylene and disposed in top and bottom positions, the two flat outer films being welded to at least two inner thermoformed blister films made from polypropylene and disposed with a repeated, regular, and continuous pattern, each of the at least two inner thermoformed blister films having a plurality of blisters and a plurality of bottoms connected to the blisters by perpendicular walls,   wherein the at least two inner thermoformed films are welded to each other with a blister-to-blister welding, or a bottom-to-bottom welding, and   wherein the two flat outer and at least two inner thermoformed films each consist of three coextruded layers,   the apparatus comprising:   an extrusion group having at least four extrusion heads each configured to produce a flat thermoplastic film;   a shaping group having at least two shaping rolls each configured to provide an indented thermoplastic film having an indented pattern defined by indentation each having a base connected to a bottom by lateral walls;   a thermowelding group downstream of the extrusion group and of the shaping group, the thermowelding group having at least two thermowelding rolls that join at least two flat thermoplastic films and at least two indented thermoplastic films by thermowelding so as to generate the sandwich panel.   
     
     
         2 . The apparatus according to  claim 1 , wherein the extrusion group, the shaping group and the thermowelding group are arranged to have:
 a first thermowelding roll facing a first shaping toll, so as to cause a first flat thermoplastic film to be shaped with the indented pattern and to be thermowelded to a second flat thermoplastic film to produce a first half of the sandwich panel;   a second thermowelding roll facing a second shaping toll, so as to cause a third flat thermoplastic film to be shaped with the indented pattern and to be thermowelded to a fourth flat thermoplastic film to produce a second half of the sandwich panel;   a third and a fourth thermowelding rolls disposed to receive the first and the second halves of the sandwich panel therebetween and to thermoweld the first and the second halves of the sandwich panel by adjoining facing bases of the first and the second halves of the sandwich panel.   
     
     
         3 . The apparatus according to  claim 2 , wherein the extrusion group, the shaping group and the thermowelding group are further arranged to have a third flat thermoplastic firm introduced between the first and the second halves of the sandwich panel, the third and fourth thermowelding rolls causing the third flat thermoplastic film to be adjoined to the facing bases of the first and the second halves of the sandwich panel. 
     
     
         4 . The apparatus according to  claim 1 , wherein the extrusion group, the shaping group and the thermowelding group are arranged to have:
 a first shaping roll and a second shaping roll each producing the indented thermoplastic film;   a first and a second thermowelding roll in facing position to cause two indented thermoplastic films to become thermowelded at respective bases thereof;   a third and a fourth thermowelding roll in facing position and disposed to receive the two thermowelded indented films and two flat thermoplastic films therebetween and to thermoweld the two thermowelded indented films and two flat thermoplastic films so as to produce the sandwich panel.   
     
     
         5 . The apparatus according to  claim 1 , wherein the extrusion group, the shaping group and the thermowelding group are arranged to have:
 a first shaping roll and a second shaping roll each producing the indented thermoplastic film;   a first and a second thermowelding roll in facing position and disposed to receive the two thermowelded indented films and two flat thermoplastic films therebetween and to thermoweld the two indented thermoplastic films by adjoining facing bases thereof and at a same time to thermoweld two flat thermoplastic films to the two indented thermoplastic films to produce the sandwich panel.   
     
     
         6 . The apparatus according to  claim 1 , further comprising one or more twin-screw extruders upstream of the extrusion group.