Foam control

Sometimes, the developer of surfactant products is compelled to use high foaming surfactants for applications in which only little foam is acceptable, e.g. in detergency and, in these cases, antifoams are necessary. Antifoams are substances or mixtures of substances which are able to reduce the foaming tendency of a system or destroy an existing foam when added in 

Silicone oils, primarily those ofthepolydimethylsiloxane-type, show a particularly prominent defoaming effect and, since they are chemically inert, they do not interfere with other components of the formulation. 

The mode of action of antifoams is usually explained by assuming that they either force surfactant molecules away from the interfaces or they penetrate interfaces that are already occupied by surfactants, thereby creating defects. These defects weaken the mechanical strength of the foam lamellae and cause their rupture. 

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Foam controllers Foamed lonomers Foamed materials Foamed plastic Foamed plastics... 

Foam Control. Whereas some siUcones are known to be foam promoters, Dow Corning FS-1265 Fluid is a Hquid fluorosiUcone with effective antifoam properties. Petroleum industry appHcation of fluids and dispersions in gas—oil separators on offshore drilling platforms has been successful. Their use peaked in the early 1980s, coinciding with constrained cmde oil capacity and production. Diesel fuels are an excellent solvent for dimethyl silicones and render them ineffective as an antifoam. A new antifoam which does not require the use of added siUca is formulated from a fluorosiUcone copolymer. It has shown promise to antifoam (8) diesel fuel (see Defoamers). 

Foam-control agents commonly are employed (see Defoamers). 

These are the components of the formulation that do all or most of the actual foam control work. Traditionally, defoamers were single component Hquids or homogeneous solutions of vegetable or mineral oils, but more recendy a number of active hydrophobic soHds have been utilized so effectively that in a dispersion of hydrophobic soHds in a traditional oil such as castor oil [8001-79-4] the oil could be classed as a carrier oil rather than an active ingredient. 

Bubble Breaker Witco Cotp. inks and coatings foam control agents... 

Special additives are often included in a carrier formulation to provide specific properties such as foam control, stabiUty, and fiber lubrication during dyeing. Most important are the solvents used to solubilize the soHd carrier-active chemicals. These often contribute to the general carrier activity of the finished product. For example, chlorinated benzenes and aromatic esters are good solvents for biphenyls and phenylphenols. Flammable compounds (flash point below 60°C) should be avoided. 

Phosphates Alkyl-alkalene diphosphates trihiityl phosphate in isopropanol Petroleum-oil systems foam control in soap solutions... 

Activities associated with bioreactors include gas/hquid contacting, on-hne sensing of concentrations, mixing, heat transfer, foam control, and feed of nutrients or reagents such as those for pH control. The workhorse of the fermentation industry is the conventional batch fermenter shown in Fig. 24-3. Not shown are ladder rungs inside the vessel, antifoam probe, antifoam system, and sensors (pH, dissolved oxygen, temperature, and the like). Note that coils may lie between baffles and the tank wall or connect to the top to minimize openings... 

Standard components for a bioreactor comprise the vessel, the agitator and impeller, heat exchangers, seals, and valves. Other components include utilities such as clean-in-place (CIP), and steam-in-place (SIP) systems, auxiliary tanks, pH and foam control, inlet tubes,... 

The use of a chemical agent as an anti-foam is affected by an on-off algorithm with variable dosing time and time delay. If the presence of foam is detected, then the controller first activates a delay timer. This type of foam controller works with some delay and variable dosing time. If at the end of the delay period the foam is still present, then the dosing pump is activated and chemical agent is added to the bioreactor. If the foam is still detected at the end of this period, the combined system of delay and dosing is reactivated. With this method of controller, addition of any unnecessary anti-foam is prevented. 

Electrode boilers produce hot water or steam (generally saturated steam) by conducting current through the BW. The water provides resistance, which causes heat to be generated when electrical current flows from one electrode to another. As a consequence, the electrical conductivity of the water is a primary factor in the satisfactory operation of these boilers. Other aspects of water treatment control (such as alkalinity levels, oxygen content, and foam control) and maintenance also must be considered if optimum efficiency is to be obtained. 

Wyandotte. Foam Control with Wyandotte Surfactants. Technical Publication. Wyandotte Chemical Corporation (now BASF AG), USA 1970. 

The combination of LAS/AE/soap provides good detergency with controlled foam [44]. The AE provides improved hardness tolerance and detergency along with foam control. Soap is used as an economically effective foam control agent, especially with LAS [45]. Some European heavy-duty powder (HDP)... 

Stabilization of emulsions Stabilization of suspensions Stabilization of foams Control of crystal growth... 

Higher alkanols, including the isomeric octyl alcohols (2-octanol and 2-ethylhexanol), cyclohexanol, lauryl and cetyl alcohols. Aliphatic alcohols have relatively poor foam control and have an odour that can be nauseous [536]. 

Polyglycols, especially poly(propylene-l,2- or -1,3-glycol). Poly(oxyethylene) and poly(oxypropylene) block copolymers have relatively poor foam control [536]. 

The unique surface characteristics of polysiloxanes mean that they are extensively used as surfactants. Silicone surfactants have been thoroughly studied and described in numerous articles. For an extensive, in-depth discussion of this subject, a recent chapter by Hill,476 and his introductory chapter in the monograph he later edited,477 are excellent references. In the latter monograph, many aspects of silicone surfactants are described in 12 chapters. In the introduction, Hill discusses the chemistry of silicone surfactants, surface activity, aggregation behavior of silicone surfactants in various media, and their key applications in polyurethane foam manufacture, in textile and fiber industry, in personal care, and in paint and coating industries. All this information (with 200 cited references) provides a broad background for the discussion of more specific issues covered in other chapters. Thus, surfactants based on silicone polyether co-polymers are surveyed.478 Novel siloxane surfactant structures,479 surface activity and aggregation phenomena,480 silicone surfactants application in the formation of polyurethane foam,481 foam control and... 

Although silicone oils by themselves or hydrophobic particles (e.g., specially treated silica) are effective antifoams, combinations of silicone oils with hydrophobic silica particles are most effective and commonly used. The mechanism of film destruction has been studied with the use of surface and interfacial tensions, measurements, contact angles, oil-spreading rates, and globule-entering characteristics for PDMS-based antifoams in a variety of surfactant solutions.490 A very recent study of the effect of surfactant composition and structure on foam-control performance has been reported.380 The science and technology of silicone antifoams have recently been reviewed.491... 

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