Mineral oil defoamers consist of approximately 85–95 % mineral oil and 1–3 % hydrophobic particles. They also contain emulsifiers, biocides and other performance-enhancing ingredients such as modified polysiloxanes. Aliphatic mineral oils are used as the carrier oil.
Emulsifiers are required in defoamers to ensure efficient dispersion of the particles in the mineral oil. They also make it easier to incorporate the defoamer in the coating formulation. As alkylphenol ethoxylates (APEO) are no longer permitted on grounds of health protection, modern mineral oil defoamers contain APEO-free emulsifiers.
In particular, high-quality defoamers for high-gloss emulsions frequently contain small amounts of a modified polysiloxane to improve the spontaneous defoaming effect. Mineral oil defoamers are the most cost-effective products in the defoamer range.