| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polycarbodiimide having a high solubility in an organic solvent and good processability and giving a product excellent in properties such as high heat resistance, low hygroscopicity, and a low permittivity by using a specified diisocyanate as the monomer and polymerizing the monomer. SOLUTION: Isocyanato groups are introduced into a diamine represented by formula III by the action of phosgene, diphenyl carbonate, or carbonyldiimidazole to obtain a diisocyanate monomer represented by formula II. The diisocyanate monomer is polymerized in the presence of a phosphorus catalyst to obtain an aromatic polycarbodiimide having structural units represented by formula I (wherein n is 2-300). Within the scope not detrimental to the properties of the polycarbodiimide, it is possible that a monomer of formula II is copolymerized with another organic diisocyanate such as 4,4'- diphenylmethane diisocyanate or that the polycarbodiimide is used in the form of a mixture after being mixed with a varnish form another polycarbodiimide.
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