Process for the production of sandwich elements from reactive plastics material

Abstract

The invention relates to a process for the production of sandwich elements (so-called panels), in which the rising reactive mixture is guided, when it rises, through guide elements arranged between the upper and lower outer layers. This process produces void-free panels having a regular cell structure. The invention also relates to an apparatus useful for the production of such sandwich elements.

1 . A process for the continuous production of sandwich elements containing (i) an upper outer layer and (ii) a lower outer layer and (iii) a layer of cellular reactive plastics material lying between (i) and (ii) and securely joined to (i) and (ii) comprising: 
 a) conveying (i) and (ii) in a longitudinal direction in a manner such that a gap extending in the longitudinal direction is formed between (i) and (ii),    b) applying a reactive mixture to (ii), and    c) contacting the reactive mixture with at least one guide element positioned between (i) and (ii) and extending over the width of (i) and (ii) as the reactive mixture rises and before the reactive mixture comes into contact with (i),    d) allowing the reactive mixture to completely react, and    e) recovering the sandwich element.    
   
   
       2 . The process of  claim 1  in which the guide element is arranged between (i) and (ii) in a manner such that rising reactive mixture reaches the guide element no sooner than when the volume of the reactive mixture applied in step b) has at least doubled, and no later than when the reactive mixture has approached the upper outer layer (i) up to a vertical distance that corresponds to the height of 3 to 5 vertically aligned cells.  
   
   
       3 . The process of  claim 1  in which the guide element is arranged between (i) and (ii) in a manner such that the reactive mixture at its rising front between (ii) and the guide element has over its height a bulge or arch formed in the transporting direction of (i) and (ii).  
   
   
       4 . The process of  claim 1  in which the guide element is vertically adjustable.  
   
   
       5 . The process of  claim 1  in which the guide element can be adjusted in the transporting direction of (i) and (ii).  
   
   
       6 . The process of  claim 1  in which the guide element can be horizontally inclined and adjusted to a desired angle.  
   
   
       7 . The process of  claim 1  in which the force exerted on the rising reactive mixture by the guide element can be adjusted.  
   
   
       8 . The process of  claim 1  in which the reactive mixture is blown in underneath the guide element with a hot gas.  
   
   
       9 . An apparatus for the continuous production of sandwich elements containing (i) an upper outer layer, (ii) a lower outer layer and (iii) a layer of cellular reactive plastics material lying between and securely joined to (i) and (ii) comprising: 
 (a) a circulating upper belt for guiding (i),    (b) a circulating lower belt for guiding (ii),    (c) a feed device for (i),    (d) a feed device (ii),    (e) a device for cutting the sandwich elements,    (f) a mixing head for applying reactive mixture to (ii),    (g) a metering device for metering each reactive component,    (h) lines between the metering device and the mixing head for conveying reactive component to the mixing head and    (i) at least one guide element arranged between and extending over the width of (i) and (ii).    
   
   
       10 . The apparatus of  claim 9  in which the guide element is vertically positioned between (i) and (ii) in a manner such that rising reactive mixture reaches the guide element no sooner than when the volume of the reactive mixture applied in step b) has at least doubled, and no later than when the reactive mixture has approached the upper outer layer (i) up to a vertical distance that corresponds to the height of 3 to 5 vertically aligned cells.  
   
   
       11 . The apparatus of  claim 9  in which the guide element can be vertically adjusted.  
   
   
       12 . The apparatus of  claim 9  in which the guide element can be adjusted in the transporting direction of (i) and (ii).  
   
   
       13 . The apparatus of  claim 9  in which the guide element can be horizontally inclined and adjusted to a desired angle.  
   
   
       14 . The apparatus of  claim 9  in which the guide element is supported with at least one mechanically or hydraulically or pneumatically acting spring element.  
   
   
       15 . The apparatus of  claim 14  in which the spring force of the spring elements can be adjusted.  
   
   
       16 . The apparatus of  claim 9  which further comprises a device containing at least one channel with at least one nozzle or slit for feeding hot gas which is arranged underneath the guide element.  
   
   
       17 . The apparatus of  claim 9  in which the guide element is flat, convex or concave in the transporting direction over its entire length or sections thereof.  
   
   
       18 . The apparatus of  claim 9  in which the guide element has a deflecting roller for (i).