Effect of Primary Amines on the Curing Reaction of Lacquer Tree Paint Film

Osamu WATANABE* and Katsutoshi NAGAI

Material Technology Department, Fukushima Technology Centre; 1-12, Machiikedai, Koriyama-shi 963-0215 Japan
Department of Materials Science and Engineering, Faculty of Engineering, Yamagata University; 4-3-16, Jonan, Yonezawa-shi 992-8510 Japan

From the knowledge of the reactivity of amines with urushiol as a main component in lacquer tree paint, effect of addition of the primary amines to the lacquer tree paint on the curing process and the light resistance was investigated to get an insight into a relationship between the curing reaction of lacquer tree paint and the molecular structure of the amines as additives. Lacquer tree paint films were added with primary amines such as diamines, star-burst-style polydiverged polymer (dendrimers) bearing amino groups, or other amino compounds, cured, and photo-irradiated.
Although primary amines immediately reacted with urushiol, their reactivity was dependent on the neighboring group of amino groups and the reaction smoothly proceeded for the amines having primary amino groups separated by long polymethylene chains. Steric structures of the amines seemed to greatly affect the reaction of amines with urushiol and the inhibition of curing reaction of lacquer tree paint film.
Furthermore, diamines and star-burst-style polydiverged polymer (dendrimer of first generation) with 4 primary amino groups worked as a nucleation reagent for microcrystallization in the lacquer tree paint films and made curing at low humidity possible.

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