Isocyanates are reactive substances. Diisocyanates have two reactive sites and react with alcohols to form polyurethanes. This reaction is called curing. Polyurethane is a polymer used for flexible and rigid foams as upholstry in furniture, in automobile interiors and for insulating purposes.
When polyurethane is exposed to severe heating, e.g. when ironing or replacing car windows, the polyurethane is broken down to isocyanates which can be dangerous.
Turnover of diisocyanates in Sweden
Source: Products Register, KemI.
The turnover of diisocyanates increases. There are six different substances used in Sweden. The most common is tolouene diisocyanate, TDI, and methylphenylmethane diisocyanate, MDI.
For occupational safety reasons more and more MDI is prepolymerised. Then the diisocyanate is partly polymerised before mixing and brought to final curing after application as binder in e.g. paint and adhesives. About 6,600 tonnes of prepolymerised MDI were used in 2007.
Breakdown between different diisocyanates 2007| Name | Short name | Number of products | Amount, tonnes |
|---|
| Methylenediphenylene diisocyanate | MDI | 503 | 6 034 |
| Tolouene diisocyanate | TDI | 212 | 4 657 |
| Isophorone diisocyanate | IPDI | 112 | 49 |
| Hexamethylene diisocyanate | HDI | 343 | 5 |
| Others | | 18 | 90 |
Source: Products Register, KemI.
The use of diisocyanates in Sweden 2007
Source: Products Register, KemI.
The use of diisocyanates as raw material for production of polyurethane plastic articles account for about 90 per cent of all use. Three per cent is used as binder in adhesives and the same amount as binders in curing paints. Two percent is used in different sealants and caulking products. Floor cover material is a clear polyurethane coating put on plastic carpets to enhance wearing qualities. It accounts for one per cent of use and so does insulating material.
