Foam Control Technology

2. Foam Control Technology

3. Historical Defoamers/Antifoam • Fat/Lard • Kerosene • Silicone fluid • Refined petroleum distillates

4. Why Is Foam A Problem? • Equipment failure • Loss of plant efficiency • Product defects • Voids in inks, paints and coatings • Adhesion loss • Spots in textiles • Safety hazard • Eyesore • Environmental hazard

5. What Causes Foam? • Foam is a result of contamination of a pure liquid • Contaminants • Dirt • Surfactants • Pigments • Metabolized waste

6. Important Things To Remember • Foam Control is generally physical, not chemical • Foam Control works because it is not similar to the foaming media • Defoamers/antifoams must be somewhat insoluble in the foaming media

7. Surfactant Chemistry • Surfactants are a chemical entity consisting of a hydrophillic (water-loving) and hydrophobic (water insoluble) tail

8. Foam Origins • A gas is entrained into the media • Mechanical • Mixers inducting air • Pump cavitation • Chemical • Reaction produces a gas

9. Bubble Physics • Ability of entrained air to escape depends upon Stokes Law. V = r2/η V = Rate of rise r = Radius of bubble η = Viscosity of media

10. Foam Formation • Once a bubble is formed, it begins to rise to the surface • As it rises, surfactants are trapped between the surface of the media and the surface of the bubble

11. Foam Stabilization • As the bubble rises it comes in close proximity to the surface of the media • A liquid lamella forms between the surface of the bubble and the media surface • The surfactants begin to orient themselves to the lowest thermodynamically stable state

12. Surfactant Orientation & Result • The hydrophillic end of the surfactant extends into the liquid lamella • The hydrophobic end resides at the surface of the media and the surface of the media

13. Stable Foam • The interaction of the charges associated with the hydrophillic heads result in a force towards the surface of the media and the surface of the bubble • Atmospheric pressure exerted on the media surface results in a force pushing in towards the media • Gas pressure from within the bubble exerts a force towards the media • Result is stable foam that can and will shut down most major equipment

14. Defoamer Vs. Antifoam • Defoamer is a term usually associated with a non-silicone foam control agent • Antifoam is usually associated with a silicone or silicone emulsion • Any foam control agent added to a pre-existing foam works as a defoamer • Any foam control agent added before the formation of foam to help prevent it is an antifoam

15. Defoamer Method Of Action • A defoamer is added to a foaming system and quickly spreads to a monolayer across the surface • Due to the rapid spreading, the underlying liquid is pulled in the direction of the spreading

16. Foam Control Begins • As the underlying liquid is pulled apart by the spreading of the defoamer, the outer lamellar wall begins to thin until it finally breaks and a hole develops in the wall • The defoamer then spills thru the hole into the liquid lamella and quickly begins to spread across the inner lamella wall

17. Foam Destabilization • As the defoamer spills into the lamella, the particulate in the defoamer attaches to the outer wall which prevents the wall from reforming due to elasticity • This repeats as the inner wall is broken

18. Bubble Rupture • As the particulate attaches to the inner wall, the lamellar fluid is expelled due the surface charge associated with the particulate • The lamlla quickly drains and thins until the the inner and outer walls are all that is left • The two walls pull away from the particulate and the gas is released

19. Factors Required For Defoaming • The liquid phase of the defoamer must have a degree of incompatability with the media into which it is dosed • The liquid must have a rapid spreading coefficient so that it spreads across the media • The hydrophobic particle works on a semi-specific contact angle, so it must be the correct size and shape

20. Defoamer Chemistry • Defoamers consist of three main components • Liquid vehicle • Emulsifier/spreading agent • Hydrophobic particle

21. Building Foam Control ProductsThe Vehicle • Does the bulk of the work • Requirements • Must be a liquid • Must have a high spreading rate coefficient • Must have some degree of incompatibility with the media

22. Building Foam Control ProductsThe Vehicle • Can be • Silicone/organosilicone oil • Vegetable oil or some derivation thereof • Synthetic polymer or ester thereof • Mineral oil/white oil • Aliphatic (paraffinic) • Naphthenic • Aromatic (mineral seal oil) • LOPS

23. Building Foam Control ProductsThe Vehicle • Hydrophobic character • Silicone/organo silicone oil • Vegetable oil or some derivation thereof • Synthetic polymer or ester thereof • Mineral oil/white oil Hydrophobicity

24. Building Foam Control ProductsThe Emulsifier/Spreading Agent • Chemical entities • Silicone/organo surfactants • Ethoxylates • Fatty esters • Alcohols

25. Building Foam Control ProductsThe Activator/Hydrophobic Particle • Chemical entities • Fatty amides • Fatty esters • Fatty alcohols • Fatty acids • Metal stearates • Silica • Urea compounds

26. Foam Control Technology