Surfactants are arguably essential components in water-based architectural coatings; there would be no water-based architectural coatings without them. Surfactants manifest in water-based architectural coatings in the following four forms.

Surfactants in antifoaming agents

Foam in water-based coatings is caused by the presence of surfactants in the system, coupled with mechanical stirring. Without antifoaming agents, the coating density would be low, and the appearance after application would be unacceptable. Therefore, antifoaming agents are essential components of water-based coatings.

However, antifoaming agents must also contain surfactants to be produced. The main components of antifoaming agents include hydrophobic particles, carriers, and emulsifiers. Carriers are usually white oil, mineral oil, etc. Without emulsifiers, these materials cannot be mixed into water-based coatings. Commonly used emulsifiers are non-ionic surfactants, such as Tweens, Spans, and fatty alcohol ethoxylates.

Surfactants in color pastes

Pigments in color pastes include organic and inorganic pigments, carbon black, etc. Different pigments have different compositions and chemical properties, and the surfactants used also differ. Suitable surfactants can only be selected based on experience and experimentation.

Soprophor BSU is a star-shaped macromolecular surfactant with excellent pigment wetting and hydrophobicity. It easily adsorbs onto the pigment surface to form a persistent and stable steric hindrance, resulting in carbon black and organic pigment pastes with good color development, low viscosity, good compatibility, and low foaming tendency.

Emulsifiers in polymer emulsions

Polymer emulsions are important components of latex architectural coatings, largely determining the physical, chemical, and mechanical properties of the paint film. The emulsion polymerization process generally requires four main substances: monomers, water, initiators, and emulsifiers. Emulsifiers play an irreplaceable role throughout the emulsion polymerization process, from micelle formation and free radical initiation to the formation of a stable dispersed polymer emulsion.

The chemical structure and combination of emulsifiers affect the performance and stability of the emulsion.

Early styrene-butadiene emulsions used SBS and OP-10 (sodium dodecylbenzenesulfonate and nonylphenol ethoxylate) as emulsifiers. Due to the environmental unfriendliness and biotoxicity of alkylphenol ethoxylates, they are now mostly replaced by alkyl alcohol ethoxylates (AEO), such as Solvay RHODASURF 6530 AP. Non-reactive emulsifiers may undergo local enrichment in the presence of water, leading to whitening and foaming of the coating. The rain streak problem often encountered in exterior coatings is also related to this. To improve the water resistance of the emulsion, reactive emulsifiers can be used, mainly some emulsifiers containing polymerizable vinyl or allyl groups. Reactive emulsifiers are anchored to the polymer and will not migrate or accumulate. For example, Reactsurf ^® 2490, etc. Reactsurf ^® 2490 can effectively prevent surfactant migration, thereby improving the stain resistance of exterior coatings.

Wetting agents

In latex paints, wetting agents can reduce the viscosity of the dispersed slurry, aid in pigment and filler dispersion, improve color development, and reduce the color difference caused by finger dragging. Excessive addition may lead to reduced water resistance and increased foaming. Traditional wetting agents are alkylphenol ethoxylates, such as NP9 and NP30, which belong to the APEO class. Currently, alkyl alcohol ethoxylates (AEO) or phosphate ethoxylates are mainly used. Phosphate ethoxylates have lower foaming tendency compared to APEOs.