ROSS Chem, Inc - Hydrite Chemical
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Transcript ROSS Chem, Inc - Hydrite Chemical
Foam Control Technology
Historical Defoamers/Antifoam
Fat/Lard
Kerosene
Silicone fluid
Refined petroleum distillates
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
What Causes Foam?
Foam is a result of contamination of a pure
liquid
Contaminants
Dirt
Surfactants
Pigments
Metabolized waste
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
Surfactant Chemistry
Surfactants are a
chemical entity
consisting of a
hydrophillic
(water-loving) and
hydrophobic
(water insoluble) tail
Foam Origins
A gas is entrained into
the media
Mechanical
Mixers inducting air
Pump cavitation
Chemical
Reaction produces a gas
Bubble Physics
Ability of entrained air to escape depends upon
Stokes Law.
V = r2/η
V=
r=
η=
Rate of rise
Radius of bubble
Viscosity of media
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
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
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
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
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
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
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
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
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
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 semispecific contact angle, so it must be the correct
size and shape
Defoamer Chemistry
Defoamers consist of three main
components
Liquid vehicle
Emulsifier/spreading agent
Hydrophobic particle
Building Foam Control Products
The 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
Building Foam Control Products
The 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
Building Foam Control Products
The Vehicle
Silicone/organo silicone oil
Vegetable oil or some derivation thereof
Synthetic polymer or ester thereof
Mineral oil/white oil
Hydrophobicity
Hydrophobic character
Building Foam Control Products
The Emulsifier/Spreading Agent
Chemical entities
Silicone/organo surfactants
Ethoxylates
Fatty esters
Alcohols
Building Foam Control Products
The Activator/Hydrophobic Particle
Chemical entities
Fatty amides
Fatty esters
Fatty alcohols
Fatty acids
Metal stearates
Silica
Urea compounds
Foam Control Technology