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 . Planar structural element ( 10 ) suitable for core layers of sandwich composite elements, containing a plurality of body segments ( 11 ) connected to one another and arranged next to one another in a plane, the body segments ( 11 ) being made of a foamed thermoplastic plastics material, wherein the structural element ( 10 ) is completely made of plastics material and the body segments ( 11 ) are welded to one another at abutting side faces to define flat weld seams ( 12 ,  13 ) intersecting in a plan view of the planar structural element ( 10 ), the flat weld seams ( 12 ,  13 ) forming a low-pore or pore-free intermediate plastics material layer made of molten plastics material of the body segments in the form of a web structure acting in a reinforcing manner and being net-like in the plan view of the planar structural element ( 10 ), and wherein the planar structural element ( 10 ) consists of a polyethylene terephthalate (PET) or a styrene/acrylonitrile copolymer (SAN). 
     
     
         22 . Planar structural element according to  claim 21 , wherein the body segments consist of a closed-cell foam. 
     
     
         23 . Planar structural element according to  claim 21 , wherein the body segments ( 11 ) are pre-cut parts made of rod-shaped or pillar-shaped foam bodies ( 7 ). 
     
     
         24 . Planar structural element according to  claim 23 , wherein the rod-shaped or pillar-shaped foam bodies ( 7 ) are produced by means of extrusion, and the extrusion direction in the body segments ( 11 ) which are produced from the foam bodies ( 7 ) is parallel or substantially parallel to the intersection line of two intersecting weld seam faces ( 12 ,  13 ). 
     
     
         25 . Planar structural element according to  claim 24 , wherein the body segments ( 11 ) have a drawing of the polymer structure oriented in the extrusion direction. 
     
     
         26 . Planar structural element according to  claim 21 , wherein the body segments ( 11 ) are joined together without gaps, and the body segments ( 11 ) have a cross section of a shape which allows the body segments to be joined together without gaps. 
     
     
         27 . Planar structural element according to  claim 21 , wherein the body segments ( 11 ), in the plan view of the planar structural element ( 10 ), have a polygonal shape and preferably an octagonal, hexagonal, quadrangular or triangular shape. 
     
     
         28 . Planar structural element according to  claim 21 , wherein the planar structural element ( 10 ) is a plastics material panel. 
     
     
         29 . Method for producing a planar structural element ( 10 ), containing a plurality of body segments ( 11 ) connected to one another and arranged next to one another in a plane, made of a foamed, thermoplastic plastics material, wherein the structural element ( 10 ) is completely made of plastics material and the body segments ( 11 ) are welded to one another at abutting side faces to define flat weld seams ( 12 ,  13 ) intersecting in a plan view of the planar structural element ( 10 ), the flat weld seams ( 12 ,  13 ) forming a low-pore or pore-free intermediate plastics material layer made of molten plastics material of the body segments in the form of a web structure acting in a reinforcing manner and being net-like in the plan view of the planar structural element ( 10 ), and wherein the planar structural element ( 10 ) consists of a polyethylene terephthalate (PET) or styrene/acrylonitrile copolymer (SAN), comprising the following steps:
 a. producing closed-cell rod-shaped or pillar-shaped foam bodies ( 7 ) having a long side;   b. welding together the rod-shaped or pillar-shaped foam bodies ( 7 ) on the long side to form a foam block ( 5 ) by superficial melting of the side faces of the body segments to be connected and subsequent joining thereof and hardening of the melt zones with the formation of flat weld seams ( 32 ,  33 ) in the form of low-pore or pore-free intermediate plastics material layers;   c. dividing the foam block ( 5 ) into individual planar structural elements ( 30 ) transverse to the longitudinal direction of the rod-shaped foam bodies ( 7 ), wherein the flat weld seams ( 32 ,  33 ) intersect in a plan view of the planar structural element ( 30 ) or meet at an angle and form a net-like web structure, and wherein the structural element ( 30 ) is produced from PET or SAN.   
     
     
         30 . Method according to  claim 29 , wherein the rod-shaped or pillar-shaped foam bodies ( 7 ) are produced by means of an extrusion process. 
     
     
         31 . Method according to  claim 30 , wherein the rod-shaped or pillar-shaped foam bodies ( 7 ) are produced with a polymer chain structure drawn in the extrusion direction. 
     
     
         32 . Method according to  claim 29 , wherein means to control the melting process during welding are provided, which allow the production of weld seams ( 12 ,  13 ) of a certain thickness range, and wherein the thickness range is selected in such a way that the net-like structure of the weld seams ( 12 ,  13 ) increases the compressive strength of the structural element ( 10 ) with respect to surface pressures. 
     
     
         33 . A structural component ( 1 ) comprising a planar structural element ( 10 ) according to  claim 21 , and a cover layer ( 2 ) applied at least on one surface of the planar structural element ( 10 ). 
     
     
         34 . Structural component ( 1 ) according to  claim 33 , wherein the structural component ( 1 ) is a sandwich composite element and wherein the planar structural element ( 10 ) is a core layer in the structural component ( 1 ). 
     
     
         35 . Structural component according to  claim 34 , wherein the sandwich composite element is a sandwich composite panel, with cover layers ( 2 ,  3 ) arranged on both sides of the core layer. 
     
     
         36 . Vane in a wind power station, comprising the sandwich composite element ( 1 ) of  claim 34 .