Methods of Making High Impact Polystyrene

A process for producing high impact polystyrene, comprising:

• feeding at least one vinyl aromatic monomer, an elastomer, and a free radical initiator to a mixing tank to form a reaction mixture;
• feeding the reaction mixture from the mixing tank to a first linear flow reactor;
• polymerizing the reaction mixture in the first linear flow reactor to a point below the point at which phase inversion occurs to produce a first polymerization mixture;
• feeding the first polymerization mixture from the first linear flow reactor to a second linear flow reactor;
• polymerizing the first polymerization mixture in the second linear flow reactor to at least a phase inversion point of the mixture to produce a second polymerization mixture;
• and
• feeding the second polymerization mixture from the second linear flow reactor to at least a third linear flow reactor for post-inversion polymerization of the second polymerization mixture, wherein a product stream leaving the at least third linear flow reactor has an environmental stress crack resistance (ESCR) value at an oven temperature of 65° C. of at least 10% toughness retained with less than 10 wt % rubber content.

A process for producing high impact polystyrene, comprising:

• feeding at least one vinyl aromatic monomer, an elastomer, and a free radical initiator to a CSTR to form a reaction mixture;
• polymerizing the reaction mixture in the CSTR to a point below the point at which phase inversion occurs to produce a first polymerization mixture;
• feeding the first polymerization mixture from the CSTR to a first linear flow reactor;
• polymerizing the first polymerization mixture in the first linear flow reactor to at least a phase inversion point of the mixture to produce a second polymerization mixture;
• and
• feeding the second polymerization mixture from the first linear flow reactor to at least a second linear flow reactor for post-inversion polymerization of the second polymerization mixture, wherein a product stream leaving the at least second linear flow reactor has an environmental stress crack resistance (ESCR) value at an oven temperature of 65° C. of at least 10% toughness retained with less than 10 wt % rubber content.