Acrylonitrile butadiene styrene (ABS) is used in the electronics, appliances, building, construction and transportation industries. A wide range of ABS thermoplastic resin products can be produced by SABIC’s Mass ABS process, which uses a proprietary mass polymerization reactor configuration and devolatization system to produce high-quality, low-volatility content product. The properties of ABS can be widely varied by using different concentrations of butadiene rubber and acrylonitrile in the polymer.
ABS production is accomplished by continuous copolymerization of styrene and acrylonitrile monomers with polybutadiene rubber (PBR) or styrene butadiene rubber (SBR) in the presence of organic peroxide, using multiple reactors in series. PBR or SBR is chopped (1) and fed to a slurry tank (2) with styrene monomer. Feed is then pumped into the ABS feed batch tank (3), where the rubber is completely dissolved. The concentrated rubber solution is diluted with fresh acrylonitrile, recovered recycle monomer and chain transfer agent according to product requirements. The combined ABS feed is preheated (4) prior to being fed to the polymerization reactors.
The polymerization section (5) uses a unique combination of plug flow and boiling stirred tank reactors operating in series. To initiate polymerization, organic peroxide is fed to the system. The reactor arrangement allows accurate control of the degree of rubber grafting, phase inversion, rubber particle size, extent of cross-linking, molecular weight and polymer morphology. Monomer conversion increases steadily through the reactor system to a final conversion of between 60%—75%. Two options for devolatization (6) are offered: extrusion devolatilization or flash chamber devolatilization. Product from the last reactor is stripped of the unreacted monomers and byproducts in an extruder devolatilization system. The temperature gradient within the extruder is set to control the degree of flashing and recovery. Alternatively, the reactor product is stripped of volatiles in a multistage flash devolatilization system that operates under deep vacuum. Vapor from the devolatization steps are condensed in a series of exchangers (7). The recovered monomer and ethylbenzene mixture stream is recycled to the upfront ABS feed preparation section. Devolatilized polymer melt is then sent to a strand cut pelletizer system (8) to create polymer strands. After the cutting and cooling steps, the pellets are dried and then classified to remove fines and over-sized pellets. The finished ABS pellets are then pneumatically conveyed to storage and packaging (9).
A broad range of ABS products are available for license. Mass ABS products are well suited for low-gloss automotive, high-heat automotive, general-purpose and pipe applications. Cycolac* mass ABS resins provide an excellent balance of processability, impact, dimensional stability and high temperature resistance with a stable light base color. Mass ABS resins are available in a wide range of melt flow rates and impact strengths for both medium- to low-gloss general-purpose molding.
*Cycolac is a trade name of SABIC Innovative Plastics.
Key features:
– High polymer yields, typically greater than 99%
– A unique reactor design for grafting, phase inversion and accurate control of rubber particle size and distribution
– Reactors incorporate special features for effective control and removal of the exothermic heat of reaction
– Uses peroxide as an initiator and grafting agent, allowing for precise particle size control
– Customizable devolatilization processes based on utility cost considerations
~ Produces medium- to low-gloss high-impact Mass ABS resins
– Produces a clean, stable base color ABS resin with low residual monomers that are ideal for coloring
– Limited polymer fouling results in turnaround frequency on the order of two years
– High safety and environmental performance in response to the more stringent regulations
