Dispersant is a kind of interfacial activator which has both hydrophilic and lipophilic properties in molecule. There are many kinds of dispersant. Today we mainly look at six types of water-borne dispersants.
Water-borne dispersants can be divided into: anionic, cationic, non-ionic, amphoteric, electrically neutral and high molecular weight hyperdispersants.
(1) Anionic surfactants: Most of them are composed of non-polar negatively charged hydrocarbon chains and polar hydrophilic groups. The two groups are located at both ends of the molecule, forming asymmetric hydrophilic and lipophilic molecular structures. Its varieties are: sodium oleate, carboxylate, sulfate (R-O-SO3Na), sulfonate (R-SO3Na), and so on. Anionic dispersants are widely used because of their good compatibility.
(2) Cationic type: compounds with non-polar positive charges. The varieties are octadecadienolamine acetate. Alkyl quaternary ammonium salt, aminopropylamine dioleate, quaternary ammonium salt, specially modified polyaminamide phosphate, etc. Cationic surfactants have strong adsorptive power and good dispersing effect on carbon black, various iron oxides and organic pigments. However, attention should be paid to their chemical reactions with carboxyl groups in the base materials, and attention should be paid not to their simultaneous use with anionic dispersants, and caution should be taken in their use.
(3) Non-ionic type: can not ionize, without charge. The adsorption on the surface of pigments is weak, and it is mainly used in water system coatings. Varieties include adduct C17H33COO (CH2 CH2O) nH of fatty acid ethylene oxide, polyethylene glycol polyols and polyvinylimide derivatives. Their function is to reduce surface tension and improve wettability. Adding some organosiloxane can prevent blooming, float and improve leveling.
(4) Amphoteric: Compounds consisting of anions and cations. Typical applications are phosphate-based polymers. This kind of polymer has high acid value, which will affect the interlayer adhesion.
Electrically neutral type: The size of anions and cationic organic groups in the molecule is basically the same. The whole molecule is neutral but polar. Varieties are: oleic acid oleate
High molecular weight (including high, middle and low molecular weight). Among them, Zui is of high grade and Zui is of high polymer type for stability. The storage stability is relatively good. Of course, we should also pay attention to not using too strong solvents, because too strong solvents will dissolve the anchoring chains of these macromolecule superdispersants under high shear stress, and then cause the pigment to coarsen and flocculate.
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