Closed mixer working process with stroke-control ram

Abstract

The invention relates to the processing, in a closed mixer ( 1 ), of polymer-based mixtures and compounds for the manufacture of tyres or components thereof. To improve the dispersion of the ingredients in the polymer base, the pressing ram ( 8 ) is lowered to the working condition controlling the position thereof over time, in order to compress the ingredients within the mixing chamber ( 4 ). The invention is particularly suitable for the dispersion of reinforcing fillers such as silica or carbon black in the polymer base and the incorporation of said fillers in the latter.

1 . Method of processing polymer-based mixtures and compounds in a closed mixer ( 1 ) comprising a mixing chamber ( 4 ), a pair of rotors ( 2 ,  3 ), a pressing ram ( 8 ) arranged above the rotors, movable between a raised resting condition which allows the introduction of material into the mixing chamber and a lowered working condition during mixing, characterized in that lowering of the ram to compress said material in the mixing chamber occurs by controlling the position-time profile of the descent of the ram, until the lower end-of-stroke position is reached.  
     
     
         2 . Method according to  claim 1 , wherein control of the position-time profile of the pressing ram ( 8 ) is performed when said ram enters into contact with the material introduced into the mixer ( 1 ).  
     
     
         3 . Method according to  claim 2 , wherein control of the position-time profile of the pressing ram ( 8 ) is performed by regulating the control pressure thereof, in such a way as to follow a predetermined reference position-time profile.  
     
     
         4 . Method according to  claim 3 , wherein the phase of lowering the pressing ram ( 8 ) is preceded by a phase of introduction into the mixer of at least one reinforcing filler of a polymer present in the mixing chamber, and wherein the descent of the ram occurs during incorporation of said filler in the polymer base.  
     
     
         5 . Method according to  claim 4 , wherein the pressing ram reaches the lower end-of-stroke position at the end of incorporation of the reinforcing filler in the polymer matrix.  
     
     
         6 . Method according to  claim 5 , wherein after the pressing ram ( 8 ) has reached the lower end-of-stroke position, plasticizers of the processed polymer base are introduced into the mixer.  
     
     
         7 . Method according to  claim 6 , wherein the reinforcing filler of the polymer base comprises at least one among silica or carbon black.  
     
     
         8 . Method according to  claim 7 , wherein the position-time profile of the pressing ram ( 8 ) is a direct processing parameter.  
     
     
         9 . Method according to  claim 1 , wherein the material introduced into the mixer ( 1 ) comprises a crosslinking system for a polymer-based mixture present in the mixing chamber ( 4 ).  
     
     
         10 . Method according to  claim 1 , wherein the material introduced into the mixer ( 1 ) comprises a mixture.