Example 4
Preparation of Surface Reformed Yellow Pigment Dispersion
Next, pH of 1 kg of SMART Yellow 3074BA (Pigment Yellow 74 surface treated dispersion, solid portion: 14.5 percent, manufactured by SENSIENT Corporation) was adjusted to 9 with tetrabutyl ammonium hydroxide solution (methanol solution) at 10 percent by mass to obtain a reformed pigment dispersion in 30 minutes. The thus-obtained reformed pigment dispersion including a pigment bonded to at least one amino benzoate group or amino benzoate tetrabutyl ammonium salt was subjected to ultrafiltering by dialysis membrane with highly deionized water, followed by ultrasonic dispersion to obtain a surface reformed yellow pigment dispersion having a pigment solid portion of 20 percent by mass.
The surface reformed yellow pigment dispersion had a 50 percent cumulative volume particle diameter (D50) of 145 nm as measured by a particle size distribution measuring instrument (NANOTRAC UPA-EX150, manufactured by NIKKISO CO., LTD.).
Preparation of Water-Dispersible Polyurethane Resin D
A thousand parts of polyester polyol P-1 was subjected to dehydration at 100 degrees with a reduced pressure. Subsequent to cooling down to 80 degrees C., 907 parts of methylethyl ketone was added followed by sufficient stirring to obtain a solution. Thereafter, 80 parts of 2,2′-dimethylol propionic acid was added to the solution.
Next, 281 parts of isophorone diisocyanate was added to allow reaction at 75 degrees C. for eight hours to complete urethanation. After the isocyanate value became 0.1 percent by mass or less, the mixture was cooled down to 50 degrees C. After 60 parts of triethyl amine was added for neutralization, 7,000 parts of water was added to obtain an aqueous solution. After removing methyl ethyl ketone from the obtained transparent reaction product under a reduced pressure at a temperature range of from 40 to 60 degrees C., water was added to adjust the concentration to obtain a stable translucent colloidal water dispersion having a nonvolatile content of 25 percent by mass.
