Clouding cloud point defoamers

In most cases, these active defoaming components are insoluble in the defoamer formulation as weU as in the foaming media, but there are cases which function by the inverted cloud-point mechanism (3). These products are soluble at low temperature and precipitate when the temperature is raised. When precipitated, these defoamer—surfactants function as defoamers when dissolved, they may act as foam stabilizers. Examples of this type are the block polymers of poly(ethylene oxide) and poly(propylene oxide) and other low HLB (hydrophilic—lipophilic balance) nonionic surfactants. 

The wash temperature has a significant effect on foaming due to its effect on the solubility of the defoaming surfactant. Nonionic surfactants are only effective above their cloud points. Careful consideration must therefore be taken when formulating with nonionics. Water hardness also plays a role in foam formation. In hard water, Ca2+ and Mg2+ form complexes with fats or anionic surfactants. These insoluble complexes interact with the foam, breaking up the micellar structure. 

The foaming properties of the nonionic surfactants depend upon the temperature because of their inverse solubility temperature relationship. Above the cloud point they are nonfoamers and some nonionic surfactants may even function as defoamers above their cloud point temperature. Therefore, the nonionic surfactant selected for rinse aid formulations must have a cloud point below the temperature of the rinse water. 

Again, the wetting and emulsification properties of the cleaning solution are very important, and in this case, the solution needs to be low foaming [28]. For example, end-capped , non-ionic surfactants used at or near their cloud point can provide these features (the low foaming nature resulting from having the separated phase acts as a defoamer). For heavily soiled surfaces, another non-ionic surfactant may have to be added in order to provide the necessary emulsification and prevent redeposition [21]. 

Since dimethicone copolyol compounds have their minimnm solnbility above their inverse cloud point, they can be used as temperature-sensitive antifoam componnds. The dimethicone copolyol will function as an emulsifier below its high cloud point, but defoam when it becomes insoluble above it. Since the dimethicone copolyol becomes soluble again on cooling, detergent formulations can be made which have minimal foam when used at high temperature, but rinse well at low temperatures. 

In some applications nonionic - surfactants (- fatty alcohol ethoxylates), which show the phenomenon of a cloud point, are used. Above their cloud point they act as defoamers, but below they may even act as foam stabilizers. Another special d. is silica that is made hydrophobic by treating it with - fatty amines. All these ingredients are used in solid or liquid (emulsion) form, with emulsifier to enhance dispersion. 

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