PURPOSE: To provide the titled pigment which has excellent resistance to solvents, water and heat and transmittance and gives high color density with fastness, by bonding an azo pigment through an aminosilane coupling agent to the surface of a core composed of fine silica powder.
CONSTITUTION: An azo pigment having a core composed of silica, such as compd. of formula III or IV, is composed of a core composed of fine silica powder having a particle size of 10μ or below and a coating of a amono- or polyazo dye chemically bonded through an aminosilane coupling agent such as a compd. of formula III or IV to the surface of the core. Azo dyes obtd. by using esterified silica gel have been prepd. in recent years, but they have disadvantages that the yields of the esterification reaction are low, the reaction must be carried out under high-temperature conditions, and the formed ester bond is highly polarized and easily undergoes hydrolysis. By chemically bonding the azo dye through the coupling agent to the core composed of fine silica powder, there can be obtd. a pigment which has good light transmittancy and give high color density with fastness.
MIYAGAWA NOBUHIRO
AZUMAGUCHI TERUAKI
NAKAGAMA SHIYOUJI
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