Лако-красочные материалы — производство

All wetting and dispersing agents are chemically surface-active agents with a characteristic amphiphilic structure comprised of
one or more hydrophobic (lipo­philic) groups along with one or more hydrophilic (lipophobic) groups in the same surfactant molecule. Due to this structure, they tend to adsorb at the inter­face, which results in decreased interfacial tension. This is the key property of surfactants determi­ning their action as wetting and dispersing agents. Surface-active compounds may be schematically represented by a tail-head model, as shown in Figure 5.3. The tail symbolizes the hydrophobic group and the head the hydrophilic group.

Surfactants are classified according to the chemical structure of their hydrophilic groups as:

• Ionic surfactants

— Anionic surfactants

— Cationic surfactants

— Amphoteric surfactants

• Non-ionic surfactants

In anionic surfactants, the hydrophobic segments are connected to anionic groups that are neutralized with cations such as sodium, potassium, ammonium, or amine ions. Some important examples of these surfactants are sulfates, sulfonates, phosphates and carboxylates (soaps). They are widely used as wetting and dispersing agents.

Cationic surfactants, having a hydrophobic group attached to the cationic group, are less common as wetting or dispersing agents for coatings compared to anionic surfactants. Derivatives of fatty amines, with hydrophobic residues in the form of cations, are an important example of this group.

Amphoteric surfactants have both anionic and cationic groups in the same molecule, and the pH value of the solution determines the predominant electrical charge on the surfactant. Examples of this class are aminocarboxylic acids and betaines.

Non-ionic surfactants are amphiphilic compounds that cannot dissociate into ions in aqueous solutions. Common examples include alkyl polyglycol ethers and alkylaryl polyglycol ethers.