Process for preparing polystyrene having a high melt flow rate

摘要

Provided is a process for preparing polystyrene having a weight average molecular weight (Mw) in the range of 120,000-160,000 g/mol, a polydispersity in the range of 4-6 and a melt flow rate of at least 40 g/10 minutes by feeding styrene into a reaction system through which the styrene passes as a component of a reaction mixture as it is polymerized, the reaction system including an initial reaction zone (100) and a downstream reaction zone (200), comprising the steps of: polymerizing styrene in the initial reaction zone to form polystyrene having a Mw of greater than 300,000 g/mol and a polydispersity in the range 1.5-2.5, 10-30 wt. % of the styrene fed to the initial reaction zone being polymerized there, —and polymerizing styrene remaining in the reaction mixture in the downstream reaction zone, a chain transfer agent being mixed with the reaction mixture at the commencement of this reaction zone and optionally at one or more additional locations within this reaction zone. The polystyrene may be used to manufacture expandable polystyrene beads or polystyrene foam board.

主权项

1. A process for preparing polystyrene having a weight average molecular weight (Mw) in the range of 120,000-160,000, a polydispersity in the range of 4-6 and a melt flow rate of a least 40 g/10 minutes by feeding styrene into a reaction system through which the styrene passes as a component of a reaction mixture as it is polymerized, the reaction system including an initial reaction zone and a downstream reaction zone, comprising the steps of: polymerizing styrene in the initial reaction zone to form polystyrene having a Mw of greater than 300,000 and a polydispersity in the range of 1.5- to 2.5, 10- to 30 wt. % of the styrene fed to the initial reaction zone being polymerized there; and polymerizing styrene remaining in the reaction mixture in the downstream reaction zone, a chain transfer agent being mixed with the reaction mixture at the commencement of the downstream reaction zone.