Defoamer
Defoamers or foam controlling agents are chemical formulations with a pronounced surface activity , which are capable of undesirable foam formation (for. Example, in waste water treatment, paper making, during the washing operation in washing machines, during painting, in fermentation processes ) to suppress or destroy foam already formed. A distinction is sometimes made between defoamers (prevent the formation of foam or dissolve foam) and deaerators (bring the air bubbles to the surface more quickly). The similar term anti-foaming agent refers almost exclusively to the field of food technology and describes substances or mixtures with identical effects. Mono- and diglycerides of fatty acids and dimethylpolysiloxane are often used.
Structural formula of a 2-monoglyceride - used as a defoamer in food
Structural formula of a 1,2-diglyceride - used as a defoamer in food
Structural formula of a triglyceride - a component of many foods
So-called compounds made from silicone oils and the silica particles implemented in them are widely used . These are heterogeneous defoamers, as these systems are insoluble in the foaming medium.
However, there are also homogeneous defoamers, i.e. H. Defoamers that are dissolved in the foaming liquor (e.g. so-called cloud point defoamers ) from the class of phosphoric acid esters:
mechanism
Various mechanisms are discussed for the effect of defoamers on foaming systems. The spreading (measure of the ability of oils and similar substances to spread over a large area) of a defoamer oil droplet that has penetrated the surface of a foam lamella plays an important role . The installation of z. B. silica particles in silicone defoamer serves the purpose of accelerating the entry of the dispersed oil droplets into the water / air interface or even enabling it.
Individual evidence
- ↑ Entry on defoamer. In: Römpp Online . Georg Thieme Verlag, accessed on August 15, 2015.
- ↑ Bodo Müller: Additives compact . 2008, ISBN 978-3-86630-915-9 ( page 54 in the Google book search).
- ↑ Entry on antifoam agents. In: Römpp Online . Georg Thieme Verlag, accessed on August 15, 2015.
- ↑ Georg Schwedt: Chemistry in everyday life for dummies . 2010, ISBN 978-3-527-70318-0 ( page 102 in the Google book search).
- ↑ Thomas Brock, Michael Groteklaes, Peter Mischke: Textbook of paint technology . 2000, ISBN 978-3-87870-569-7 ( page 166 in the google book search).