Process for Preparing High Impact Monovinylaromatic Polymers in the Presence of a Borane Complex

Abstract

The present invention relates to a process for preparing a high impact monovinylaromatic polymer comprising admixing a rubber, at least one monovinylaromatic monomer and optionally one or more comonomer in the presence of at least a borane complex of the L-BH 3 type wherein L is a Lewis base and polymerizing the monovinylaromatic monomer. The borane complex initiator, L may be an ether (e.g THF, tetrahydrofurane), a thioether (e.g dimethylthioether) or an amine. A preferred complex is an amine borane such as by way of example triethylamine borane. The present invention also relates to a high impact monovinylaromatic polymer having a weight ratio of grafted monovinylaromatic monomer and optional comonomer to the initial monovinylaromatic monomer and optional comonomer above 0.1%, advantageously above 2% and preferably in the range 2 to 4%. The invention is of particular interest to make high impact polystyrene.

1 - 15 . (canceled) 
     
     
         16 . A high impact monovinylaromatic polymer comprising a grafting rate of at least 0.1%. 
     
     
         17 . The high impact monovinylaromatic polymer of  claim 16 , having a grafting rate of at least 2%. 
     
     
         18 . The high impact monovinylaromatic polymer of  claim 17 , having a grafting rate in the range of 2 to 4%.