Methods for Production of High Impact Polystyrene Having an Improved Rubber Morphology

Abstract

A high impact polystyrene reactor system includes a first continuously stirred tank reactor. The first continuously stirred tank reactor includes an inlet configured to receive (i) at least one vinyl aromatic monomer, (ii) an elastomer, and (iii) a free radical initiator; and an outlet configured to convey a first reactor effluent. In addition, the high impact polystyrene reactor system includes a second continuously stirred tank reactor. The second continuously stirred tank reactor includes an inlet in fluid communication with the first continuously stirred tank reactor outlet and configured to receive (i) a portion of the first reactor effluent from the first continuously stirred tank reactor, (ii) at least one vinyl aromatic monomer, (iii) an elastomer, and (iv) a free radical initiator; and an outlet configured to convey a portion of a second reactor effluent comprising high impact polystyrene. Further, the high impact polystyrene reactor system includes a conduit for establishing a recirculation stream between the second reactor and the first reactor. The recirculation stream comprises another portion of the second reactor effluent.

What is claimed is: 
     
         1 . A high impact polystyrene reactor system, comprising:
 a first continuously stirred tank reactor including:
 an inlet configured to receive (i) at least one vinyl aromatic monomer, (ii) an elastomer, and (iii) a free radical initiator; and 
 an outlet configured to convey a first reactor effluent; 
   a second continuously stirred tank reactor including:
 an inlet in fluid communication with the first continuously stirred tank reactor outlet and configured to receive (i) a portion of the first reactor effluent from the first continuously stirred tank reactor, (ii) at least one vinyl aromatic monomer, (iii) an elastomer, and (iv) a free radical initiator; and 
 an outlet configured to convey a portion of a second reactor effluent comprising high impact polystyrene; and 
   a conduit for establishing a recirculation stream between the second reactor and the first reactor, wherein the recirculation stream comprises another portion of the second reactor effluent.   
     
     
         2 . The reactor system of  claim 1 , wherein the first continuously stirred tank reactor is arranged vertically with the inlet at the top and the outlet at the bottom. 
     
     
         3 . The reactor system of  claim 1 , wherein the vinyl aromatic monomer is a styrene, a substituted styrene, an unsubstituted styrene or any combination thereof. 
     
     
         4 . The reactor system of  claim 1 , wherein the elastomer is a polymer of butadiene. 
     
     
         5 . The reactor system of  claim 1 , wherein the recirculation stream from the second continuously stirred tank reactor is conveyed to the first continuously stirred tank reactor at a rate ranging from about 0.1% of a volume of the second continuously stirred tank reactor per minute to about 20% of a volume of the second continuously stirred tank reactor per minute. 
     
     
         6 . The reactor system of  claim 1 , wherein the high impact polystyrene has a rubber particle size of from about 1 micron to about 10 microns. 
     
     
         7 . The reactor system of  claim 1 , wherein the high impact polystyrene has a rubber particle size distribution of less than about 1.5. 
     
     
         8 . The reactor system of  claim 1 , wherein the high impact polystyrene has occlusions ranging in size from about 0.1 microns to about 2 microns. 
     
     
         9 . The reactor system of  claim 1 , further comprising one or more additional linear flow reactors for receiving at least a portion of the second reactor effluent.