Polyurethanes (MDI, TDI, polyols): Production route
Why isocyanates are made in only a few dozen complexes
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.Polyurethane is not made in one plant: it is assembled from two streams. Isocyanates (MDI and TDI) are made in a few dozen large, chlorine-integrated complexes, because phosgene is too toxic to ship. Polyols are made in many more plants, usually beside a propylene oxide unit. Converters and systems houses then react the two. The sub-products below cover the main chemistries, plus the emerging low-carbon and phosgene-free options.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| MDI (methylene diphenyl diisocyanate) | about 8.6 Mt demand (2025), the largest isocyanate | about 0.74 t aniline (0.62 t benzene), 0.12 t formaldehyde, 0.79 t phosgene (about 0.57 t chlorine) per t (stoichiometric, indicative) | 300-700 kt/yr per train; Wanhua Fujian adds 700 kt/yr in 2026 (faxiangongchang) | high, over 95% on aniline (indicative) | about 0.58 t HCl per t (stoichiometric) | not published; MDI averaged about $2,110/t in China in September 2025 (faxiangongchang) |
| TDI (toluene diisocyanate) | about 3.3 Mt demand (2025, indicative); China about 45% of capacity | about 0.53 t toluene, 0.72 t nitric acid, 1.14 t phosgene (about 0.82 t chlorine) per t (stoichiometric, indicative) | 150-500 kt/yr; Covestro Shanghai moving to a 500 kt/yr tier (faxiangongchang) | high (indicative) | about 0.84 t HCl per t (stoichiometric) | not published; China TDI CNY 14,300-14,500/t in H2 2025 (faxiangongchang) |
| Polyether polyols | the bulk of polyols; China capacity about 7.48 Mt/yr in 2023 plus over 2.5 Mt added since (faxiangongchang) | about 0.85-0.95 t PO plus initiator for flexible grades (indicative) | 100-500 kt/yr, usually beside a PO plant | near-quantitative | few; catalyst residues | about PO plus $150-300/t (indicative) |
| Polyester polyols (aromatic and aliphatic) | minority of polyols (indicative) | varies; aromatic types can use recycled PET | 10-100 kt/yr | high | water | not published |
| Lower-carbon and phosgene-free options | below 1% (indicative) | CO2 replaces up to about 20% of fossil feed in cardyon polyols (indicative) | pilot to small commercial | n/a | n/a | premium, not published |
How each route works
MDI (methylene diphenyl diisocyanate)Benzene is nitrated and hydrogenated to aniline, condensed with formaldehyde to methylene dianiline, then phosgenated. Distillation splits pure (monomeric) MDI from polymeric MDI. HCl co-product is recycled to chlorine or sold.
Versatile and profitable for scale leaders; needs integrated chlorine, nitric acid and aniline.
faxiangongchang 2026; stoichiometry TDI (toluene diisocyanate)Toluene is nitrated to dinitrotoluene, hydrogenated to TDA and phosgenated. Mostly sold as the 80:20 isomer blend for flexible slabstock foam.
Cheapest isocyanate for slabstock foam; more toxic and volatile than MDI.
faxiangongchang 2026; stoichiometry Polyether polyolsPropylene oxide (with some ethylene oxide) is polymerised onto an initiator such as glycerine (flexible foam) or sucrose and sorbitol (rigid foam) using KOH or double-metal-cyanide catalysts.
Simple, cheap chemistry; price follows PO and propylene.
faxiangongchang 2026; ISOPA polyols eco-profile 2021; indicative Polyester polyols (aromatic and aliphatic)Glycols are esterified with adipic acid (elastomers, coatings) or with phthalic anhydride, PTA or recycled PET (aromatic polyester polyols for rigid insulation boards).
Good fire and solvent resistance; an outlet for recycled PET.
PU Europe aromatic polyester polyol eco-profile; indicative Lower-carbon and phosgene-free optionsCO2-based polyols (Covestro cardyon), bio-based or mass-balance aniline and polyols, polyols recovered from foam by glycolysis (Dow RENUVA), and non-isocyanate polyurethanes from cyclic carbonates.
Lower fossil content; small scale and higher cost.
indicative; PO tile (RENUVA) Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.