# Polyurethanes (MDI, TDI, polyols): Production route

Why isocyanates are made in only a few dozen complexes

Source page: https://www.materialinsights.org/chemicals/polyurethanes/routes/

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 polyols**

Propylene 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 options**

CO2-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.

## Other sections

- [Summary](https://www.materialinsights.org/chemicals/polyurethanes/index.md)
- [Overview](https://www.materialinsights.org/chemicals/polyurethanes/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/polyurethanes/correlation/index.md)
- [Production](https://www.materialinsights.org/chemicals/polyurethanes/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/polyurethanes/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/polyurethanes/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/polyurethanes/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/polyurethanes/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/polyurethanes/regulation/index.md)
- [Characteristics](https://www.materialinsights.org/chemicals/polyurethanes/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/polyurethanes/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/polyurethanes/links/index.md)