Method for preparing diisocyanate by heat decomposition

Abstract

The present invention discloses a method for preparing diisocyanate by thermally separating diamino formic ether. The method comprises the following steps that fatty group or alicyclic group diamino formic ether undergoes a thermal decomposition reaction for 0.5 to 2.5 hours in the presence of a catalyst at a reaction pressure of between 1.0 and 1.5 atmospheric pressure and a reaction temperatureof between 50 and 240 DEG C so as to form fatty group or alicyclic group diisocyanate. The catalyst is easy to obtain and can be recycled, the reaction conditions are mild, the cost and the energy dissipation are reduced, the byproduct of the reaction is recoverable alcohol that does not cause contamination to environment, and thus the method is more suitable for the large scale industrial production.

Description

technical field [0001] The invention relates to a method for preparing aliphatic or alicyclic diisocyanate, in particular to a method for preparing aliphatic or alicyclic diisocyanate by using a diurethane thermal decomposition method. Background technique [0002] Compared with aromatic isocyanates, aliphatic diisocyanates do not contain carbon-carbon unsaturated double bonds in their molecules, and the polyurethane coatings prepared by them have color retention, gloss retention, chalking resistance, oil resistance, wear resistance, yellow resistance and high decorative properties. Therefore, it has been widely used in the fields of coatings, adhesives, synthetic leather, etc. Isocyanate (PAPI) and phenyl isocyanate (PI) are another type of isocyanate that is in greater demand. [0003] Aliphatic diisocyanate includes 1,6-hexamethylene diisocyanate (referred to as HDI), 1,5-pentane diisocyanate, 1,7-heptane diisocyanate, 1,8-octyl diisocyanate, 1,10-decane diisocyanate, te...

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Problems solved by technology

[0014] At present, the research on the method of preparing isocyanate mainly by thermal decomposition of carbamate by liquid phase method is relatively in-depth, wherein, US4613466 discloses copper, zinc or zinc-nickel, zinc-copper alloy, decomposes HDU at 370 ℃ (two n-butyl ester) reaction, can obtain the HDI of high yield, but there is reaction temperature higher in this invention, and the defect that used catalyst can not be reclaimed; CN101195590 discloses a kind of method that takes HDU as raw material catalytic pyrolysis to prepare HDI, and this invention uses Ionic liquid is used as the reaction medium, and supported metal oxide is used as the catalyst. At 200°C, vacuum 10mmHg, and react for 1.5 hours, the yield of HDI is 69-88%. However, the cost of the product is greatly increased due to the high price of the reaction medium.

[0015] However, the method disclosed in the prior art to thermally decompose carbamate to prepare isocyanate using a liquid phase method is still not suitable for large-scale industrial production.