Phosphate dispersants are a mixture of mono-, di-, residual alcohols and phosphoric acid.
Phosphate ester dispersants stabilize pigment dispersions, including reactive pigments such as zinc oxide. In gloss coating formulations, it can improve gloss and cleanability. Unlike other wetting and dispersing agents, the addition of phosphate dispersants does not affect the KU and ICI viscosity of the coating.
Polyacid homopolymer dispersants such as Tamol 1254 and Tamol 850, which is a methacrylic acid homopolymer. Polyacid copolymer dispersant, such as Orotan 731A, which is a copolymer of diisobutylene and maleic acid. The characteristics of these two types of dispersants are: strong adsorption or anchoring on the surface of pigments and fillers; longer molecular chains to form steric hindrance; chain ends are water-soluble; Stable results. To make the dispersant have good dispersibility, the molecular weight must be strictly controlled. If the molecular weight is too small, the steric hindrance is insufficient; if the molecular weight is too large, flocculation will occur. For polyacrylate dispersants, a polymerization degree of 12-18 can achieve the best dispersion effect.
Other types of dispersants, such as AMP-95, have a chemical name of 2-amino-2-methyl1-propanol. The amino group is adsorbed on the surface of the inorganic particles, and the hydroxyl group extends into the water, and plays a stabilizing role through steric hindrance. Due to its small molecule, steric hindrance is limited. AMP-95 is mainly a pH regulator.
In recent years, research on dispersants has overcome the problem of flocculation caused by high molecular weight, and its development towards high molecular weight is one of its trends. For example, the high molecular weight dispersant EFKA-4580 produced by the emulsion polymerization method is specially developed for water-based industrial coatings. It is suitable for the dispersion of organic and inorganic pigments and has good water resistance.
Through acid-base or hydrogen bonding, amino groups have a good affinity for many pigments. Block copolymerization and dispersing agents based on aminoacrylic acid have gained attention.