Overview
Isocyanate curing agents are various esters of isocyanic acid. It is generally believed that cyanic acid and isocyanic acid are tautomers, and isocyanic acid is mainly generated when in equilibrium. The structure of isocyanate is R—N═C═O. People have not yet found esters equivalent to cyanic acid. The naming of isocyanates is similar to that of carboxylates, and people called isocyanate or isocyanate curing agent. For example: butyl isocyanate, phenyl isocyanate, 2,4-diisocyanate.
Synthesis of isocyanate curing agent
Among isocyanate curing agents, aromatic isocyanates are more important. Phosgene reacts with primary amines to first generate carbamoyl chloride, which decomposes into isocyanate under heat. For example: 2RNH2+COCL2→RNHCOCL+RNH2.HCL, RNHCOCL→R—N═C═O+HCL Isocyanate is an unpleasant tear-inducing liquid. There is a carbon atom connected to two double bonds in the isocyanate molecule, which is similar to the structure of ketone. It has active chemical properties and can react with various compounds with active hydrogen, such as water, alcohol, amine, etc., and people can use it as a curing agent.
Performance
The N-phenyl carbamate and N,N’-disubstituted urea generated by phenyl isocyanate, an isocyanate curing agent, have a certain melting point. We can use it to identify alcohols, phenols and primary and secondary amines. Diisocyanates and diols can generate polyurethane polymer compounds (polyurethane resins). For example, adipic acid and ethylene glycol are first condensed to generate polyester. This low molecular weight polyester has two hydroxyl groups at both ends, so people can use it as a diol to react with toluene-2,4-diisocyanate to obtain polyurethane resin. This polymer is also a good elastomer, so it is also a synthetic rubber. This is the performance of isocyanate curing agent.
To produce foam plastics, you can add a small amount of water to the diol during the preparation process. A small amount of phenyl diisocyanate can also react with water during the polymerization process. The process can generate diamines and carbon dioxide. When people polymerized and cured the product, small bubbles formed by carbon dioxide. They remain in the polymer to form a sponge-like foam plastic.
Related Links: Synthesis of bisphenol A epoxy resin, CAS No 77 89 4, CAS No 77 93 0, Dimethyl Glutarate, High Purity Tributyl Citrate Plasticizer
