The dispersant is also called a wetting dispersing agent. In addition to its wetting effect, its active group can be adsorbed on the surface of the pigment pulverized into fine particles at one end, and solvated into the lacquer base to form an adsorption layer at the other end (the more the adsorption group, the more the chain link Long, the thicker the adsorption layer, generates charge repulsion (aqueous paint) or entropy repulsion (solvent-type paint), so that the pigment particles are dispersed and suspended in the paint base for a long time to avoid re-flocculation, thus ensuring storage stability of the finished paint system. .
There are many types of dispersants, and it is estimated that there are more than 1,000 substances in the world that have a dispersion effect. Now distinguished by its structure, it can be divided into the following seven types.
1 Anionic wetting and dispersing agent
Most of it consists of a non-polar negatively charged oleophilic hydrocarbon chain moiety and a polar hydrophilic group. The two groups are located at both ends of the molecule to form an asymmetric hydrophilic lipophilic molecular structure. Its varieties are: sodium oleate C17H33COONa, carboxylate, sulfate salt (R-O-SO3Na), sulfonate (R-SO3Na) and so on. Anionic dispersants are well compatible and are widely used in waterborne coatings and inks. Polycarboxylic acid polymers and the like are also applicable to solvent-based coatings and are widely used as controlled flocculating dispersing agents.
2 cationic wetting and dispersing agent
It is a non-polar base group positively charged compound, and mainly has an amine salt, a quaternary ammonium salt, a pyridinium salt and the like. Strong adsorption of the cationic surfactant, carbon black, various iron oxide, organic pigments dispersed better, but note that compound with a carboxyl group from chemical reactions, but also pay attention not to be used with an anionic dispersant.
3 non-ionic wetting and dispersing agent
It is non-ionizing and non-charged in water, and it is weakly adsorbed on the surface of pigments, mainly used in water-based paints. Mainly divided into ethylene glycol and polyol type, reducing surface tension and improving wettability. Used as a wetting or emulsifying agent in combination with anionic dispersants, it is widely used in aqueous colorants, water-based paints and inks.
4 Amphoteric wetting and dispersing agent
It is a compound composed of an anion and a cation. Typical applications of the polymer is phosphate ester salt type. These polymers have higher acid numbers and may affect interlayer adhesion.
5 electric neutral wetting and dispersing agent
The anion and cationic organic groups in the molecule are substantially equal in size, and the entire molecule is neutral but polar. Such as oil amino oleate C18H35NH3OOCC17H33, etc. are all of this type, and are widely used in coatings.
6 polymer type hyperdispersant
Polymeric dispersants are the most commonly used and have the best stability. The polymer type dispersant is also classified into a polycaprolactone polyol-polyethyleneimine block copolymer type dispersant, an acrylate polymer type dispersant, a polyurethane or a polyester type polymer dispersant, etc., due to their The anchoring group is entangled with the resin and the other end is coated with the pigment particles, so the storage stability is better.
7 controlled free radical type hyperdispersant
The latest controlled free radical polymerization technology (CFPP) allows the structure of the dispersant to be more regular. Commonly used methods are: GTP, ATRP (atomic transfer radical polymerization), RAFT (reversible addition fragmentation chain transfer controlled radical polymerization, including C-RAFT and S-RAFT, etc.), NMP, SFRP (stable free radical polymerization) , TEMPO, etc. By using controlled radical polymerization technology, the relative molecular mass distribution of the dispersant can be more concentrated, the anchoring groups are more concentrated, and the efficiency is higher.
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