Reaction of Formic Acid with Hexamethylene-Diisocynate

3 Reaction of Formic Acid with Hexamethylene-Diisocynate 

For the thermokinetic meastirement, the batch of hexamethylene-diisocyanate is brought to the reaction temperature 90 °C and a small amount of formic acid (p.a.) instantly injected to start the reaction. The injection causes an instantaneous, large heat stroke, and the pressure rises slightly. Then follows a monotonous decrease in the thermal reaction power accompanied by a slow increase in pressure. The same goes for the instant addition of larger amounts or for the successive addition of small amotmts. Continuous, constant dosing causes a quick and linear temperature increase and a slow increase in the pressure. At the end of dosing the increase in temperature stops abruptly and at this moment the temperature starts to decay. 

The analysis of the produced gas shows for all cases a mixture of CO2 and CO. The relation of the components in samples of gas, taken during the further course of the reaction, changes favourably for CO. 

From the heat stroke in the initial phase the quantity 59 kJ/molA results as heat from the process. The value is much larger than the value of a usual physicochemical process (e.g. heat of mixture). 

However, this variety arises perceptibly only at reaction temperatures above 50 °C by consecutive reactions with the surplus hexamethylene-diisocynate. There also occur side reactions of subsequent products, separating CO. 

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