Extensional flow heat exchanger for polymer melts

Abstract

An extensional flow static heat exchanger with at least two components of tubular cooling elements arranged in a flow passage, wherein the components are successively arranged in the flowing direction, each component having a first and a second set of at least two cooling elements, the cooling elements of the first set being angularly offset to the cooling elements of the second set, the cross sections of the cooling elements have a convex profile on the upstream and downstream side or a droplet shape, the cooling elements of the first and the second set, respectively of the adjacent component are arranged at least partially in the space between two cooling elements of the first and second set, respectively of the previous component, a process for producing a low density extruded thermoplastic foam material and a low density extruded thermoplastic foam material.

1 . An extensional flow static heat exchanger ( 10 ) with at least two components ( 20 ) of tubular cooling elements ( 25 ) arranged in a flow passage adapted to be flown through by a flow medium in a flowing direction, characterized in that
 the components ( 20 ) are successively arranged in the flowing direction,   each component ( 20 ) comprises a first set ( 21 ) and a second set ( 22 ) of at least two cooling elements ( 25 ), wherein each cooling element comprises at least two cooling tubes,   the cooling elements ( 25 ) of the first ( 21 ) and the second set ( 22 ) are spaced substantially parallel to each other in a plane running substantially perpendicularly to the flowing direction,   the cooling elements ( 25 ) of the first set ( 21 ) being angularly offset to the cooling elements of the second set ( 22 ) with respect to the longitudinal axis of the flow passage, and   the cross sections of the cooling elements ( 25 ) have a convex profile on the upstream and downstream side with regard to the flow direction or a droplet shape,   the cooling elements ( 25 ) of the first set ( 21 ) of the adjacent component ( 21   b ) are arranged at least partially in the space between two cooling elements ( 25 ) of the first set ( 21 ) of the previous component ( 21   a ), and   the cooling elements ( 25 ) of the second set ( 22 ) of the adjacent component ( 22   b ) are arranged at least partially in the space between two cooling elements ( 25 ) of the second set ( 22 ) of the previous component ( 22   a ).   
     
     
         2 . The extensional flow static heat exchanger ( 10 ) according to  claim 1 , wherein the cooling elements ( 25 ) of the first set ( 21 ) are positioned in a 90°±5° angle to the cooling elements ( 25 ) of the second set ( 22 ). 
     
     
         3 . The extensional flow static heat exchanger ( 10 ) according to  claim 1 , wherein the first set ( 21 ) of cooling elements ( 25 ) are arranged in a distance to the second set ( 22 ) of cooling elements ( 25 ) of not less than 50% and not more than 200% in reference to the diameter of one tube of a cooling elements ( 25 ). 
     
     
         4 . The extensional flow static heat exchanger ( 10 ) according to  claim 1 , wherein the tubes of the cooling element ( 25 ) are arranged with a distance of not less than 0.5 cm and not more than 6 cm. 
     
     
         5 . The extensional flow static heat exchanger ( 10 ) according to  claim 1 , wherein a vacuum area is positioned downstream after the exchanger ( 10 ) exit. 
     
     
         6 . The extensional flow static heat exchanger ( 10 ) according to  claim 1 , wherein the cooling elements ( 25 ) of the first ( 21 ) and second ( 22 ) set of the adjacent component ( 21   b ,  22   b ) are arranged tessellated to the cooling elements ( 25 ) of the first ( 21 ) and the second ( 22 ) set of the previous component ( 21   a ,  22   a ). 
     
     
         7 . A process for producing low density extruded thermoplastic foam material wherein a polymer-gas mixture is fed into an extensional flow static heat exchanger ( 10 ) according to  claim 1 . 
     
     
         8 . The process according to  claim 7 , wherein the polymer material is a thermoplastic material, virgin or recycled, or a mixture or blend of any of them. 
     
     
         9 . The process according to  claim 7 , wherein the polymer-gas mixture further includes at least one of nucleating agent(s), flame retardant(s), or elastomeric impact modifier(s). 
     
     
         10 . The process according to  claim 7 , wherein the cooling elements ( 25 ) of the extensional flow static heat exchanger ( 10 ) are cooled down to a temperature not more than 10° C. above the solidification point of the polymer-gas mixture. 
     
     
         11 . The process according to  claim 7 , wherein the polymer material is PET, PBT, PC, PEEK, PEI, PMI, PMMA, PS, PVC or PA, or a mixture or blend of any of them. 
     
     
         12 . The process according to  claim 7 , wherein at least 75% of the polymer material is PET. 
     
     
         13 . The process according to  claim 12 , wherein the PET material comprises at least 70% recycled, post-consumer PET (r-PET). 
     
     
         14 . The process according to  claim 12 , wherein the cooling elements ( 25 ) of the extensional flow static heat exchanger ( 10 ) are cooled down to a temperature between 265° and 285° C. 
     
     
         15 . A low density extruded thermoplastic foam material with a density between 12 kg/m 3  to 50 kg/m 3  according to ISO 845, which is obtainable by the process according to  claim 7 . 
     
     
         16 . The low density extruded thermoplastic foam material according to  claim 15  with a density between 12 to 50 kg/m 3 , which is obtainable by reactive extrusion of PET resin. 
     
     
         17 . A foamed article manufactured from a material according to  claim 15 .