PRIO – A tool for Risk Reduction of Chemicals

Isocyanates

Isocyanates are used as a raw material in the production of polyurethane (PUR), which occurs in plastic and as a binder in adhesives, paints and varnishes.

Polyurethane is formed following a reaction between diisocyante and a compound with several hydroxyl groups, a polyol. The use of diisocyanates is increasing in Sweden as increasing numbers of polyurethane products are being produced (link till brief statistics on isocyanates).

Isocyanate is a chemical substance that contains the group -N=C=O on an alkyd chain or an aromatic ring. The substance group of isocyantes can be divided into mono-, di- and polyisocyanates depending on the number of isocyanate groups. Diisocyanates, which have two reactive isocyanate groups, are the most widely used, and the most common are diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diiocyanate and isophorone diisocyanate. The Swedish Chemicals Agency has drawn up flow analyses and substance information for some isocyanates.

Isocyanates occur as both liquids and powder. The liquids can give off vapours that are already hazardous at room temperature. Many isocyanates are classified, here you can search in the Classification List for individual isocyanates. It can generally be said that isocyanates can cause allergies on skin contact or inhalation, damage to the respiratory organs when vapours or aerosols are inhaled. Certain isocyanates can cause cancer. Some are also classified as environmentally harmful, as they are toxic to aquatic organisms.

The problems in the working environment can be reduced by making the diisocyanates less volatile or reactive. There are two ways of doing this, either by pre-polymerising or pre-reacting the diisocyanates, or by blocking them. In both cases, a larger molecule is brought about. There are, however, always residues of free diisocyanate in pre-polymerised or blocked products.

Preventive measures are import in work with isocyanates. The Work Environment Authority has issued regulations on work with thermosetting plastics containing isocyanates, AFS 1996:4.

Further information:

Hazardous chemicals in textiles. Report of a government assignment. Rapport från ett regeringsuppdrag. KemI Report 3/13, april 2013

Tillsynsprojektet härdplaster (Supervisory project on thermosetting plastics), Report from the Swedish Chemicals Inspectorate 4/91, 1991.

National Board of Occupational Safety and Health Arbetarskyddsstyrelsens notice with regulations on thermosetting plastics AFS 1996:4

Classification List, index 615 Cyanates and isocyanates.