Reactive extrusion of styrene polymers

Abstract

SYNOPSISReactive extrusion is the term used to denote a plastics processing method in which an extruder is used as a reactor for the continuous synthesis and modification of polymers. This paper describes the manufacture of polystyrene and styrene-isoprene copolymers by a reactive extrusion process: anionic "living" s-butyllithium-initiated bulk polymerization was performed in a co-rotating closely intermeshing twin-screw extruder. The results of the process analysis show that living polymerization of styrene can be performed in a screwtype reactor, despite the high reaction temperatures of over 200°C. The polystyrene melt can be modified in bulk with comonomers or coupling reagents immediately after polymer synthesis. Depending on the raw material, formulation, and process parameters, the process variants developed and analyzed at the Institut fur Kunststoffverarbeitung for homopolymerization of styrene, copolymerization of styrene-isoprene mixtures, and sequential polymerization of styrene and isoprene resulted in styrene polymers with widely differing structural characteristics and properties. For example, the copolymerization of styreneisoprene monomer mixtures produced poly [ isoprene-co-styrene) 4-styrene] . The sequential polymerization of styrene and isoprene led to poly ( styrene-b-isoprene) contaminated with partly cross-linked low molecular weight polyisoprene. The polyisoprene content is presumably formed by side reactions due to the high reaction temperatures. 0 1993

Towards the control of the reactivity in high temperature bulk anionic polymerization of styrene, 1. Influence ofn,s-dibutylmagnesium on the reactivity of polystyryllithium species

“…According to Kern 3) , the thermal degradation of polystyryllithium proceeds by lithium hydride elimination and formation of an unsaturated chain-end. In order to control the run-away process on a technical scale, the bulk anionic polymerization of styrene in the presence of s-butyllithium has been performed in an extruder at 200 8C 4) . However, to preserve the main advantages of living anionic styrene polymerization under high temperature and bulk conditions, the overall reactivity of the active species should be drastically reduced.…”

Reactive extrusion of poly(urethane‐isocyanurate)

“…1 The modular corotating twin-screw extruder (TSE), developed during the 1950s by Bayer AG and Werner & Pfleiderer GmbH, has been applied to polymerization processes since the 1960s. 1,2 There have been several investigations on the application of these extruders to reactive extrusion of various polymers such as polyamides, 2 polylactides, 3 polystyrene, 4 and melamine-formaldehyde. 5 Many patents have also appeared associated with the use of TSE for continuous polymerization of urethanes.…”

Styrene/butadiene copolymer synthesized by reactive extrusion

“…Based on the above reasons, Michaeli [2] successfully synthesized polystyrene (PS) using a co-rotation twin screw extruder with diameter of 30 mm and reactor R/D of 29 using s-butyllithium as the initiator. The reaction temperature was 50 C to 230 C from zone 1 to zone 6 and the conversion was almost 100%.…”