Foam is generated in textile applications mainly by surfactants and surfactant blends which are used as textile
auxiliaries during processing. Since foam is disturbing machine runnability, antifoams are currently used. They
have to be highly efficient in foam suppression and foam knock down.Defoamer efficiency is dependent on the
foaming system.This is why the selection of a suitable defoamer is needed in every specific case. Defoamer
efficiency can be determined by preliminary screening tests or a new defoamer has to be developed to match the
particular requirements.
When antifoams are used for pre-defoaming of surfactant concentrates, they must be stable and should not separate
from the blend during storage. Defoamer stability is especially a problem in textile auxiliaries with a high water
content.This is because antifoams must be partially incompatible with the system to be defoamed. If the textile
auxiliary already has a high water content, this can result in a negative influence on the stability of the
antifoams. Besides the water content, the whole composition of the textile auxiliary is crucial for the stability
of the antifoams.
Antifoams are often added in prediluted form to highly diluted aqueous systems in which they have to provide a
reliable foam control. In this case, the antifoam has to be stable under several conditions, such as: shear forces,
elevated temperatures, presence of electrolytes or high alkalinity.
Antifoams must be free of side-effects, like spotting, and should have minimum impact on possible subsequent
treatments (for example printability). Improved dispersability and re-dispersability are beneficial properties.
Antifoam dosage varies in a broad range. Concentrations of 0.005 % up to 0.2 % are currently used and must be
optimized by preliminary tests.
Requirements for Antifoams:
- High efficiency
- Stable in concentrates
- No negative side effects
