It has good film-forming properties for PVP, is soluble in water, insoluble in certain organic media, and forms a transparent film that does not affect the original color. It can also enhance the gloss and dispersibility of pigments. It is often used as a surface coating agent for organic azo pigments. The molecular weight Mw of the PVP polymer used for cladding must be greater than 300,000. Its thickness is generally between 0.001 and 1.6μ, and the pigment particle size is approximately 0.1 to 10μ. For every 100 parts of pigment, 5 to 100 parts of polymer are required. Generally, the polymer accounts for 20 to 50% of the core weight of the pigment. NVP can also be copolymerized with a small amount of ethylene unsaturated compounds, especially acrylate types, such as stearate acrylate, hydroxyl-substituted alkyl ester of acrylic acid and other copolymers as coating agents.
