Process for the production of a double-layer metal sheet and a more particularly stove enamelled shaped constructional member shaped therefrom, and also a deep-drawable double-layer metal sheet

Abstract

The invention relates to a process for the production of a double-layer metal sheet, more particularly a lacquered shaped construction member comprising such a double layer metal sheet, for example, for the outer skin of a motor vehicle, having an intermediate layer ( 6 ) of epoxy resin glued to the two smooth cover sheets ( 7, 10 ). After the introduction between the cover sheets ( 7, 10 ) of the intermediate layer ( 6 ) and of spots ( 16 ), distributed over the surface, of an epoxy resin polymerizing at a lower temperature than the epoxy resin of the intermediate layer ( 6 ), the cover sheets ( 7, 10 ) are fixed spatially in relation to one another by the polymerization of the epoxy resin of the spots ( 16 ). Then the resulting composite is shaped. Finally the shaped constructional member ( 15 ) obtained is lacquered and the epoxy resin of the intermediate layer ( 6 ) polymerized during stove enamelling.

1 . A process for the production of a double layer metal sheet having an intermediate layer ( 6 ,  26 ,  27 ) of an epoxy resin in the form of a hot melt glued to its cover sheets ( 7 ,  10 ,  20 ,  21 ),.  
       characterised in that after the introduction between the cover sheets ( 7 ,  10 ,  20 ,  21 ) of the intermediate layer ( 6 ,  26 ,  27 ) of an epoxy resin polymerising (cross-linking) only at a higher temperature, more particularly stove enamelling temperatures, and of spots ( 16 ,  32 ), distributed over the surface, of another epoxy resin which polymerises at a lower temperature than the polymerisation temperature of the epoxy resin of the intermediate layer ( 6 ,  26 ,  27 ) and which can still be shaped to a limited extent in the polymerised state, the cover sheets ( 7 ,  10 ,  20 ,  21 ) are spatially fixed in relation to one another at spots ( 16 ,  32 ) in contact therewith by the heating of their polymerising epoxy resin to the lower temperature.  
     
     
         2 . A process according to    claim 1    and further processing to give a more particularly stove enamelled shaped constructional member,  
       characterized by the following further steps: 
 a) the double-layer metal sheet with the cover sheets ( 7 ,  10 ,  20 ,  21 ) attached to one another is deformed to give the shaped constructional member ( 15 ) with the epoxy resin of the intermediate layer ( 6 ,  26 ,  27 ) not yet polymerised,  
 and  
 b) after the deforming, more particularly after the lacquering of the deformed constructional member ( 15 ), said constructional member ( 15 ) is heated to the higher temperature, more particularly the stove enamelling temperature, at which the polymerisation of the epoxy resin of the remaining intermediate layer ( 6 ,  26 ,  27 ) takes place, more particularly simultaneously with the enamelling of the lacquer.  
 
     
     
         3 . A process according to claims  1  or  2 ,  
       characterised in that the intermediate layer ( 6 ,  26 ,  27 ) is introduced over its whole area between the cover sheets ( 20 ,  21 ), more particularly by the coil coating process, small compression-resistant bodies ( 31 ) of epoxy resin being scattered in for the spots ( 32 ).  
     
     
         4 . A process according to claims  1  or  2 ,  
       characterised in that the intermediate layer ( 7 ) is provided with suitable receiving spaces ( 4 ) prior to the introduction of the spots ( 16 ).  
     
     
         5 . A process according to claims  1  or  2 ,  
       characterised in that the intermediate layer used is a perforate foil.  
     
     
         6 . A process according to claims  4  or  5 ,  
       characterised in that the receiving spaces ( 4 ) are filled for the spots ( 16 ) with an epoxy resin which does not foam under the action of heat.  
     
     
         7 . A process according to claims  4  or  5 ,  
       characterised in that the receiving spaces ( 4 ) are only partially filled for the spots ( 16 ) with an epoxy resin which foams under the action of heat.  
     
     
         8 . A process according to    claim 1   ,  
       characterised in that during the introduction of the intermediate layer ( 26 ,  27 ) and the spots ( 32 ) between the cover sheets ( 20 ,  21 ), followed by joining, due to their higher compressive strength the spots ( 32 ) are forced into contact with the cover sheets ( 20 ,  21 ) by the intermediate layer ( 26 ,  27 ).  
     
     
         9 . A process according to one of    claims 1    to    8   ,  
       characterised in that the double-layer metal sheet is heated to the lower temperature inductively or steadily by a heating press ( 12 ) which contacts the cover sheets ( 7 ,  10 ) or by heated rollers continuously contacting the cover sheets ( 20 ,  21 ).  
     
     
         10 . A deep-drawable double-layer metal sheet having two metal cover sheets ( 7 ,  10 ,  20 ,  21 ) and an intermediate layer ( 6 ,  26 ,  27 ) of epoxy resin disposed between the coversheets ( 7 ,  10 ,  20 ,  21 ), more particularly for use in a process according to    claim 2    and more particularly in conjunction with one of    claims 3    to    9   ,  
       characterised in that embedded in the intermediate layer ( 6 ,  22 ,  23 ), distributed over the cover sheets ( 7 ,  10 ,  20 ,  21 ) are adhesive spots ( 16 ,  32 ) which fix the sheets spatially in relation to one another and which consist of a polymerised epoxy resin whose polymerisation temperature is lower than the polymerisation temperature of the epoxy resin of the intermediate layer ( 6 ,  26 ,  27 ).  
     
     
         11 . A deep-drawable double-layer metal sheet according to    claim 10   ,  
       characterised in that the two cover sheets ( 7 ,  10 ,  20 ,  21 ) have different strengths of material, more particularly different thicknesses.