Polystyrene Process by INEOS Technologies

The INEOS polystyrene (PS) technology is based on a bulk continuous process giving access to a wide range of general purpose polystyrene (GPPS) also known as crystal polystyrene and high-impact polystyrene (HIPS), which incorporates rubber particles for high shock absorbance.

The process yields a variety of superior products with attractive investment and conversion costs. These products
are sold and well accepted worldwide. INEOS offers commercially proven swing-line technology, capable of producing both GPPS and HIPS grades, with capacities ranging from 60,000 tpy up to 200,000 tpy that provide a turndown capability of 60%.

Polystyrene Process by INEOS Technologies

The INEOS PS technology can be divided into several key processing operations as follows:

Rubber dissolving (1): Polybutadiene rubber, in bale form, is chopped into crumbs. To enhance dissolving, preheated styrene is introduced into a high-shear in-line mixer. This operation allows high capacity production of dissolved rubber at a high rubber concentration.

Prepolymerization (4): Prepolymerization is conducted in the first two reactors that are CSTR-type with proprietary agitator designs. Prepolymerization may be thermally or chemically initiated depending on the desired product. For HIPS, this is a critical phase of the process since this is where the rubber morphology and physical properties of the resultant product are controlled.

Polymerization (5): Polymerization is conducted in the last reactor, which is a plug-flow type of proprietary design allowing high efficiency heat removal and temperature control on viscous media.

Devolatilization (7): This is a two-step operation under high vacuum, to remove lights components such as unreacted styrene and diluent, which is enhanced with the addition of a foaming agent in the second stage. The stripping effect of the foaming agent reduces the residual monomer content to as low as 200 ppm.

Recycle recovery (8): Unreacted styrene and diluents from the devolatilization operation are distilled and recycled to the front end of the process. The distillation of the recycle stream ensures that only styrene and ethylbenzene are recycled back to the first pre-polymerization reactor to ensure that the styrene purge is minimized and the oligomer concentration in the reactor system is kept low. Two purges are provided to control the accumulation of light and heavy components in the PS unit: a lights purge consisting of styrene and ethylbenzene and a heavy purge consisting of oligomers and other heavy organics. These purges are used as fuel for the hot oil heater.

fig 1 149 - Polystyrene Process by INEOS Technologies

Finishing: This section consists of filtering the polymer melt, extruding it into strands, cutting them into cylindrical pellets of prescribed size, sorting the resultant pellets from fines and oversize pellets and conveying the product pellets to a quality control silo.

Process features:
• Proprietary rubber grinding and dissolving unit
• Catalyzed polymerization:
o Enhanced polymer/rubber grafting
o Reduced oligomers byproducts
• Proven proprietary prepoly reactor design allowing temperature and morphology control
• Proprietary plug-flow reactor design => outstanding temperature control, highest conversion rates, rubber morphology preservation
• High-efficiency devolatilization system
• LP steam generation system
• Ongoing development of new and improved formulations.

Client benefits:
• High rubber efficiency
• Low-investment cost and inventory on the rubber section
• Excellent rubber yields
• High consistency and high product quality thanks to rubber morphology control
• Minimized capital investment
• High reliability
• Best in class residual SM on final product
• Fast transitions, high prime quality yields
• Consistent, high quality products
• Lowest utility consumption among licensed technologies
• Market penetration into new applications.

Licensor: INEOS Technologies


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