Anionic High Impact Polystyrene: A New Process for Low Residual and Low Cost HIPS

BASF has developed a new process for the manufacturing of High Impact Polystyrene (HIPS) via an anionic route: the so-called A-HIPS process. The driving forces were the development of a product with a low content of residuals and improved cost performance compared to the radical state of the art HIPS. The production of A-HIPS includes the synthesis of the rubber, a styrene-butadiene block copolymer. To overcome the main challenges of anionic polymerization such as reactivity control, solvent purity and initiator costs, BASF has developed its own proprietary technology, the Retarded Anionic Polymerization (R.A.P.) which allows styrene polymerization to 100% conversion under similar reaction conditions as the radical polymerization. A new low cost anionic initiator system (BuLi-free), based on sodium hydride and triethylaluminum, has been developed for perfect reactivity control over a broad temperature and concentration range even up to bulk conditions.