Foamed plastic sheet

Abstract

An unmixed plastic sheet, which is made of a thermoplastic material and which is composed of a number of body segments that are adjacent to one another in a plane, interconnected and made of a closed-cell foam material. The body segments are thermoplastically welded to one another at their abutting lateral faces while forming flat weld seams. The flat weld seams form a plastic intermediate layer, which has few pores, and which is provided in the form of a web structure that, when viewed from above, is reticular and reinforces the plastic sheet. The inventive plastic sheet is preferably used as a core layer in sandwich composites.

1 - 20 . (canceled)  
     
     
         21 . a structural element ( 10 ) comprising a plurality of body segments ( 11 ) of a foamed, thermoplastic material that are arranged next to each other and joined together on a plane, wherein the structural element ( 10 ) is made wholly of plastic and the body segments ( 11 ) are welded together at abutting side faces forming weld seams ( 12 ,  13 ), whereby the weld seams ( 12 ,  13 ) form a substantially pore-free intermediate plastic layer in the form of a network of stiffening struts.  
     
     
         22 . A structural element according to  claim 21 , wherein the body segments are made of a closed-cell foam material.  
     
     
         23 . A structural element according to  claim 22 , wherein the thermoplastic material is polyethylene-terephthalate (PET) or styrene/acrylnitrile-copolymer (SAN).  
     
     
         24 . A structural element according to  claim 21 , wherein the weld seams comprises melted plastic of the body segments ( 11 ).  
     
     
         25 . A structural element according to  claim 24 , wherein of the weld seams ( 12 ,  13 ) have a thickness such that a network-like strut structure is formed by the weld seams which increases the compressive strength of the structural element ( 10 ) with respect to surface pressure.  
     
     
         26 . A structural element according to  claim 21 , wherein the body segments ( 11 ) are formed from lengths cut from rod-shaped or column-shaped foam bodies ( 7 ).  
     
     
         27 . A structural element according to  claim 26 , wherein the rod-shaped or column-shaped foam bodies ( 7 ) are formed by means of extrusion, and the direction of extrusion in the body segments ( 11 ) manufactured from the foam bodies ( 7 ) lies substantially parallel to a line of intersection of two crossing weld seam ( 12 ,  13 ).  
     
     
         28 . A structural element according to  claim 27 , wherein the body segments ( 11 ) comprises a stretched polymer structure in a direction of extrusion.  
     
     
         29 . A structural element according to  claim 21 , wherein the body segments ( 11 ) have a cross-section which enables the body segments to be fitted together without interruption.  
     
     
         30 . A structural element according to  claim 21 , wherein the body segments ( 11 ) have a polygonal shape.  
     
     
         31 . A structural element according to  claim 21 , wherein the structural element ( 10 ) is a plastic sheet.  
     
     
         32 . A process for manufacturing a structural element ( 10 ) comprising a plurality of body segments ( 11 ) arranged adjacent to one another in a plane and interconnected comprising the following steps: 
 a) manufacture of closed-cell rod-shaped or column-shaped foamed plastic bodies ( 7 ) having long sides;    b) welding together the long sides of the rod-shaped or column-shaped foamed bodies ( 7 ) into a plastic block ( 5 ) thus creating weld seams ( 32 ,  33 ) over a face, whereby the said weld seams ( 32 ,  33 ) are present as substantially pore-free intermediate plastic layers to form a block of foamed plastic; and    c) dividing the block ( 5 ) of foamed plastic into individual structural elements ( 30 ) comprising foam sheets, running transverse or perpendicular to the longitudinal direction of the rod-shaped foam bodies ( 7 ),    whereby the weld seams ( 32 ,  33 ), as viewed in plan view of the structural element ( 30 ), form a network like structure of struts.    
     
     
         33 . A process according to  claim 32 , comprising the step of manufacturing the rod-shaped or column-shaped foam bodies ( 7 ) by an extrusion process.  
     
     
         34 . A process according to  claim 33 , wherein the rod-shaped or column-shaped foam bodies ( 7 ) are manufactured using a polymer chain structure that is stretched in the direction of extrusion.  
     
     
         35 . A process according to  claim 32 , wherein the weld seam is formed by melting the faces of the sides of the body segments ( 11 ) to be joined and subsequently fitting the faces together and solidifying them.  
     
     
         36 . A process according to  claim 35 , including providing means for controlling the melting process during welding to enable weld seams ( 12 ,  13 ) of a specific thickness range to be produced such that the network strut structure of weld seams ( 12 ,  13 ) increases the compressive strength of the structural element ( 10 ) with respect to surface pressures.  
     
     
         37 . A process according to  claim 32 , wherein structural element ( 10 ) is of a thermoplastic material and the welding of the body segments ( 11 ) is a thermoplastic welding process.  
     
     
         38 . A process according to claims  32 , including providing the structural component ( 1 ) with an outer layer ( 2 ) deposited on at least one surface of the structural element ( 10 ).  
     
     
         39 . A process according to  claim 38 , the structural component ( 1 ) forms a core layer which is a sandwich type composite element with outer layers ( 2 ,  3 ) on both sides of the core layer.