Polycarbonate: Production route
Phosgene or melt: two routes to a clear plastic
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.Two routes make almost all polycarbonate. The older interfacial route reacts BPA with phosgene in a two-phase system of dichloromethane and caustic soda. The melt route reacts BPA with diphenyl carbonate (DPC) without solvent, releasing phenol that is recycled. Asahi Kasei's version makes DPC from CO2 and ethylene oxide, avoiding phosgene altogether. Feed is BPA in every case, so integration back to phenol and BPA decides cost.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Interfacial phosgene process | about 50-55% (indicative) | about 0.9 t BPA and 0.39 t phosgene (stoichiometric), with about 0.28 t chlorine and caustic soda consumed (indicative) | 100-260 kt/yr lines; Hengli and SSTPC each 260 kt/yr (findoutaboutplastics) | about 98% on BPA (indicative) | sodium chloride brine (recyclable to chlor-alkali) | BPA about $1,080/t of PC at about $1,200/t BPA plus about $300-400/t for phosgene, solvent and conversion (indicative) |
| Melt transesterification (non-phosgene) | about 45-50% (indicative; most new Asian capacity) | about 0.9 t BPA and 0.84 t DPC, with about 0.74 t phenol recovered (stoichiometric) | 100-260 kt/yr | about 98% (indicative) | phenol (recycled); monoethylene glycol in the Asahi Kasei route | similar to interfacial; avoids solvent (indicative) |
| Blends and copolymers (PC/ABS, PC/PBT, siloxane copolymers) | a large share of the 5.2 Mt includes blends (findoutaboutplastics) | typically 50-80% PC (indicative) | compounding lines 10-100 kt/yr | not published | none | premium to base PC (indicative) |
How each route works
Interfacial phosgene processBPA is dissolved in caustic soda and reacted with phosgene in dichloromethane at low temperature. The polymer is washed, the solvent stripped and recycled, and the resin pelletised. It gives very good optical quality.
Best optical grades; handles highly toxic phosgene and chlorinated solvent.
indicative; BPA price basis from BPA tile Melt transesterification (non-phosgene)BPA and DPC are heated under vacuum with a catalyst; phenol distils off and is recycled to make DPC. Asahi Kasei's process makes DPC from CO2, ethylene oxide and methanol via ethylene carbonate and dimethyl carbonate.
No solvent or phosgene in the PC step; harder to make very low-yellowness optical grades.
indicative Blends and copolymers (PC/ABS, PC/PBT, siloxane copolymers)PC is compounded with ABS for processability or with PBT for chemical resistance. Copolymers with siloxane or other bisphenols add low-temperature impact or heat resistance.
Tailored grades; harder to recycle.
indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.