Process for continuous synthesis of a diene elastomer

Abstract

A process for the continuous synthesis of diene elastomers with a high degree of conversion is provided. The process includes simultaneously: a) introducing continuously into a polymerisation reactor containing a gas phase and equipped with at least one stirring rotor and a discharge device, at least i. one or more monomers, including at least one conjugated diene monomer, and ii. from 0% to 70% by mass of an organic solvent, calculated relative to the total mass of monomers and of solvent, b) continuously polymerising the monomer(s), c) stirring the polymerisation medium via the continuous movement of at least one stirring rotor about a rotary axle, d) continuously discharging the elastomer paste, e) continuously conveying the discharged elastomer paste to a chopping device and chopping it into particles, f) removing solvent from the particles of the elastomer paste, and g) recovering diene elastomer.

1 . An installation for performing a process for continuous synthesis of a diene elastomer, comprising a polymerisation reactor containing a gas phase and equipped with at least one stirring rotor and a discharge device, said reactor being at least equipped with:
 several inlets connected, respectively, to several feed sources including at least one source feeding said reactor with catalytic system or polymerisation initiator, a source feeding said reactor with at least one monomer and a source feeding said reactor with inert hydrocarbon-based solvent,   an outlet which removes from said reactor, continuously, said elastomer paste as an exiting stream connected via said discharge device to a device which chops said discharged elastomer paste,   two stirring rotors including twin sigma or z-shaped arms stirring said reaction medium, and   a discharge device including at least one emptying screw.   
     
     
         2 . The installation according to  claim 1 , wherein said reactor includes a tank, each of said sigma or z-shaped arms is supported on both of two opposite sides of said tank, and said arms are each driven about a rotary axle that is horizontal. 
     
     
         3 . The installation according to  claim 1 , wherein said arms are imbricated and driven in rotation with fixed speed ratios. 
     
     
         4 . The installation according to  claim 1 , wherein said arms are tangential and are driven in rotation independently of each other. 
     
     
         5 . The installation according to  claim 1 , wherein said arms are driven counter-rotatively. 
     
     
         6 . The installation according to  claim 1 , wherein said process for continuous synthesis of said diene elastomer has a residence time distribution function in said polymerisation reactor having a standard deviation that is greater than said mean residence time divided by 2√3, and wherein said installation provides a degree of conversion of at least 60%, at a limit of a first third of a reaction volume of said polymerisation reactor. 
     
     
         7 . The installation according to  claim 1 , wherein said discharge device comprises at least one emptying screw, at an end of which is connected a gear pump. 
     
     
         8 . The installation according to  claim 1 , wherein said device for chopping said elastomer paste discharged from said reactor into particles is a granulator. 
     
     
         9 . The installation according to  claim 8  wherein said granulator is an underwater granulator. 
     
     
         10 . The installation according to  claim 1 , further comprising, at said outlet of said reactor, a blender of self-cleaning type sweeping at least 90% of a volume of said blender, at least equipped with an inlet connected to a source for feeding with said elastomer paste discharged from said polymerisation reactor, an outlet adapted for removing from said blender, continuously, said elastomer paste as an exiting stream towards said granulator. 
     
     
         11 . The installation according to  claim 10 , wherein a discharge device of said blender includes at least one emptying screw, at an end of which is connected a gear pump. 
     
     
         12 . The installation according to  claim 10 , wherein at least one from among said reactor and said blender is provided with a second outlet to a condenser. 
     
     
         13 . The installation according to  claim 12 , wherein said condenser is provided with an outlet for bringing a condensate to said reactor, and/or to said blender. 
     
     
         14 . The installation according to  claim 1 , wherein, when said polymerisation is performed by coordination catalysis and when said reactor is fed with a catalytic system, said installation comprises a source for feeding with an alkylaluminium directly connected to said polymerisation reactor or connected to a mixture of streams and upstream of said polymerisation reactor, on condition that said feeding with said catalytic system takes place independently of said mixing of said streams. 
     
     
         15 . The installation according to  claim 1 , wherein said process for said continuous synthesis of a diene elastomer, comprises, simultaneously:
 a) introducing continuously into said polymerisation reactor containing said gas phase and equipped with two stirring rotors including twin sigma or z-shaped arms and said discharge device, at least   i. said at least one monomer to be polymerised, including at least one conjugated diene monomer, and   ii. from 0% to 70% by mass of said solvent, calculated relative to a total mass of said monomer(s) and of said solvent   b) continuously polymerising said monomer(s),   c) stirring said polymerisation medium via continuous movement of said stirring rotors about a rotary axle,   d) continuously discharging said elastomer paste derived from said polymerisation,   e) continuously conveying said discharged elastomer paste to said chopping device and chopping it into particles,   f) removing said solvent from said particles of said elastomer paste, and   g) recovering said diene elastomer of said particles obtained in step f); wherein   (1) said process has a degree of conversion of at least 60%, at a limit of a first third of a reaction volume of said polymerisation reactor, and   (2) said process has a residence time distribution function in said polymerisation reactor having a standard deviation that is greater than said mean residence time divided by 2√3.   
     
     
         16 . The installation according to  claim 15 , wherein said degree of conversion is at least 80%, at a limit of said first third of said reaction volume of said polymerisation reactor. 
     
     
         17 . The installation according to  claim 15 , wherein said standard deviation of said residence time distribution function in said polymerisation reactor is greater than said mean residence time divided by 2. 
     
     
         18 . The installation according to  claim 15 , wherein said stirring of said polymerisation medium is performed by continuous movement of said two stirring rotors. 
     
     
         19 . The process according to  claim 15 , wherein, in step e), said elastomer paste discharged is conveyed to a granulator for chopping said elastomer paste.