Construction of high-branched derivatives based on melamine for highly effective defoaming and antifoaming.

Foams can be seen everywhere in human production and life. An uncontrolled foam event usually leads to product losses, equipment damage, and clean-up costs. Defoamer is one of the most effective strategies to eliminate or inhibit foam activities, which has been proved by long-term practices. In this work, we report new molecular defoamers with high-branched structure, which adopts melamine molecule as the parent structure, by incorporating alkyl-isocyanates with different chain lengths into the high-branched melamine derivatives (Hb-MDs) formula to replace the R - NH (primary ammonia) on melamine structure. The substitution reaction processes can be readily tuned by varying the molar ratio or alkyl chain length of alkyl-isocyanate, enabling a facile control over the branched degree. The foam tests reveal that the high-branched melamine molecule defoamers exhibited excellent defoaming and anti-foaming properties for four typical foam systems, including an anionic SDBS, cationic DTAB, non-ionic AEO-9, and white cat (BM) detergent, with efficiency close to that of silicone-type LN1414 defoamer and far superior to that of high-carbon alcohol XS-02 defoamer, at the same addition level. Notably, the defoaming or anti-foaming performances of the high-branched melamine molecule defoamers were not always monotonically increased with the branched degree or hydrophobic chain length, but a suitable range needed to be maintained to support a good balance of defoamer structure with foam liquid films. Therefore, it is anticipated that this high-branched design principle could open a new avenue for the construction of molecular defoamers for complex industrial problems.