Isocyanate, a general term for various esters of isocyanic acid (HNCO), the more important compounds are alkyl monoisocyanates, (substituted) phenyl monoisocyanates, a-substituted benzyl isocyanates, polyisocyanates and other four categories, among which Common ones are toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), polymethylene Chemicalbook-based polyphenyl polyisocyanate (PAPI) and hexamethylene diisocyanate (HDI) etc. Due to their different characteristics, they are widely used in the preparation of plant protection agents, insecticides, herbicides, plant growth regulators and antitumor drugs, etc. Their high polymers can be used to synthesize pigments, resins, textile hydrophobic agents, plastics , detergents, foams, elastomers, adhesives and coatings, etc.