Foam control hydrophobic material

Reliance on the reaction of hardness ions with soap or alkyl phosphate ions to form calcium soap or calcium alkyl phosphate precipitates for foam control has an obvious limitation in the case of soft water. This factor has encouraged a search for alternative materials that can also form finely divided hydrophobic particles. Hydrocarbon waxes represent an obvious choice in this context. 

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. 

New copolymerization methods, additives, rubber modification, and blending have made of polystyrene polymer and copolymers versatile packaging materials. Developed in 1930 by BASF, polystyrene (PS) is commonly produced by the continuous bulk polymerization of styrene in the presence of ethylbezene that control product viscosity and heat transfer. PS is hydrophobic, nonhygroscopic, and easily processed by extrusion and thermoform-ing. Three types of PS are available general-purpose, impact PS, and foams. 

In this class of materials, the careful control of monomer feed and reaction conditions allows the preparation of surfactants in which such characteristics as the hydrophile-lipophUe balance (HLB), solubility, wetting, and foaming properties can be closely and reproducibly controlled. The classification of these surfactants is based primarily on the nature of the initiator employed in the formation of the initial polymer block, with subclasses determined by the compositions of the various blocks. In fact, there is no need for the initiator in these materials to be particularly hydrophobic the hydrophobicity is derived from one of the two polymeric blocks. Typical initiators would be monohydric alcohols such as butanol and dihydric materials (glycol, glycerol and higher polyols, ethylene diamine, etc.). A generic alkylene oxide molecule can be represented by... 

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