Injury to the respiratory tract by isocyanates used in making lacquers.

Bayer, Rinke, Siefken, Orthner, and Schild in 1937 and 1942 demonstrated the possibility of producing high molecular compounds with extraordinary chemical and physical properties by means of a so-called diisocyanate-polyaddition procedure. The basic reaction, leading to low-molecular products, had been known for about 100 years. Bayer and his colleagues were able to show, however, that the reaction between a diisocyanate, e.g., 1,6-hexanediisocyanate and a divalent alcohol, e.g., 1,4-butylene-glycol, led to the formation of a linear polymer, a polyurethane that could be spun. This product was given the name " perlon U". If the reaction takes place between a diisocyanate and compounds with more than two hydroxyl groups, e.g., alkydresins with free OH-groups, one obtains high-molecular compounds with a network structure. Through the variation of the polyester types (the alkydresins) it is possible so to change the properties of the final product that one gets hard and brittle products of alkyds built upon glycerol and phthalic acid as well as soft and elastic products ofalkyds built upon aliphatic carbonic acids and glycols. The dior tri-isocyanates have been given the trade name " desmodur " with varying designations according to particular type, while the polyesters are called " desmophen". Of over 100 diisocyanates, only about 15 can be produced technically. Of interest are the "desmodur" types T, TH, and THN. " Desmodur T" consists of a mixture of 60% m-tolylene diisocyanate and 40% p-tolylene diisocyanate. It is a fluid with low viscosity with a flash point of + 1320 C. and melting points of + 5 to + 70 C. At the time of the cases described in this paper probably only " desmodur TH" was used in Sweden. This is a compound of 3 mol." desmodur T " and 1 mol. hexane triol (Bayer, 1947). It consists of an almost odourless resinous mass which appears commercially dissolved in a solvent such as ethyl acetate or in a mixture of ethyl acetate and toluene. It contains about 15% of the primary substance " desmodur T" (Reinl, 1953). More recently, Farbenfabrik Bayer in Leverkusen has also produced " desmodur THN", whose composition is not known to us. In this product, too, however, one may probably assume that there are traces of " desmodur T". The isocyanates are chemically extraordinarily reactive and combine easily with primary NH2-groups, water, alcohols, carbonic acids, phenols and, in general, with compounds having a reactive hydrogen atom which may theoretically be replaced with an alkali metal.