Why is MDI production considered one of the highest-barrier chemical processes globally?

Why is MDI production considered one of the highest-barrier chemical processes globally?
MDI synthesis involves a long route including nitration, reduction, and phosgenation—the latter being the only industrially viable large-scale method. Phosgene is highly toxic and requires strong acid conditions, demanding exceptional equipment and process control. MDI also reacts readily with water and has a low freezing point, complicating storage and transport. These factors create steep entry barriers, which is why capacity remains concentrated among a few players. Wanhua Chemical's expansion to 380,000 tonnes/year by early 2024, including a Fujian site scaling from 80,000 to 150,000 tonnes/year, underscores how mastering these challenges enables aggressive capacity growth that reshapes global supply dynamics.