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Introduction
In
many industry fields, foam is a disturbing agent.
In the sugar production above all from beets, foam is a prioritary
problem as well in the inside as in the outside operations.
Entrapped air bubbles in the material used for paper manufacture can
cause breaking of the sheet. Air contained in the stock can also affect
negatively the quality, for example sheet formation, of end product and
cause a higher energy absorption of the pumps.
Foam is also undesirable in the production of dispersion paints, because
of the possible crater formation during the application.
In biotechnical processes, e.g. during the production of penicillin,
enzymes, citric acid, glutammic acid and so on, foam causes difficulties
in controlling the reaction and may produce e reduction in the yield.
In mechanical and biological sewage plants foam causes clarification
problems and environmental pollution.
Action
mechanism
Foam
is normally formed by the action of a surfactant (natural or syntethic)
that is a chemical product containing in its molecule a hydrophilic and
a lipophilic group. In a phase interface the hydrophilic group is
directed to the water and the lipophilic to the fat or to the air. This
allows the formation of a very stable thin layer of liquid which
includes air, that is a foam bubble.
The defoamer must be able to distroy this equilibrium and to permit the
air to escape. For this reason the defoamer is always insoluble in water
and must come slowly to the surface (of the bubble or of the water). In
many cases a certain disperdibility in the water is desired in order to
have a better distribution in the medium and to reach the single
bubbles.
Choice of the suitable defoamer
As already said, there are several product categories having a
defoaming effect and in many cases it is not possible to establish in
advance which one will be the most suitable for a specific case. We can
tray to make a list pointing out the most important characteristics. In
any case we suggest to do the necessary tests with the specific medium.
Our technicians are at your disposal to suggest the best way to carry
out the tests and eventually to do them together with you.
Fat defoamers: Not very effective, good against foam caused by
surfactant occurring in nature, normally biodegradable
Silicone defoamers: Very effective, often undesired because of
the substantivity of silicone
Defoamers containing
metal soaps: Very effective, normally good against foam caused by
synthetic surfactants.
Wax and fat dispersion
defoamers: Not very effective, normally used where it is desired a
good compatibility with the medium to defoam in order to avoid strong
and sudden reactions, for example in paper production
Defoamers containing
alkylene oxides: Often used in the food industry and
biotechnologies. Better effective at higher temperature.
DEFOAMERS FOR
THE SUGAR INDUSTRY
Products
range
|
Type
|
Chem.
base
|
Colour
|
Active
cont
|
Main
field of application
|
|
Nexfoam
ZAF 10
|
fatty
alcohol/brown fatty acid
|
brown
|
100%
|
transport
waters
|
|
Nexfoam
ZDI 20
|
fatty
alcohol alcowylated
|
pale
yellow
|
100%
ca
|
extraction/concentr
|
|
Nexfoam
ZDI 50
|
fatty
alcohol alcoxylated
|
pale
yellow
|
50%
ca
|
extraction
|
|
Nexfoam
FER
|
fatty
alcohol alcowylated
|
clear
|
100%
ca
|
fermantation
|
|
DEFOAMERS FOR
THE PAPER INDUSTRY
Products
range
|
Type
|
Chem.
base
|
Colour
|
Active
cont
|
Main
field of application
|
|
Nexfoam
OCT
|
fatty
acid alcoxylated
|
yellow
|
100%
|
tissue
|
|
Nexfoam
ACT
|
alcohol
emulsion
|
white
|
30%
ca
|
paper
stock
|
|
Nexfoam
MAS
|
fatty
alcohol alcoxylated
|
pale
yellow
|
100%
ca
|
paper
stock
|
|
Nexfoam
PAT
|
metal
soap
|
yellow
light brown
|
100%
ca
|
coating
|
|
Nexfoam
AS1
|
fatty
acid/ alcohol
|
brown
|
100%
ca
|
waste
water
|
|
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