Defoamers and Deaerators

Defoamers and deaeration additives contained in the past mineral oils as active component but they are not anymore used in Europe. In emulsions, mineral oil can amount up to 10% mass content maximum. If defoamers and deaeration additives are used at a maximum of 0.1% in paper production [22], per each ton of paper, a maximum of 1,000 g defoamers and deaeration additives are used which contain 100 g mineral oil. In consideration of a 50% retention on the fibres, a theoretical content of 50 mg mineral oil per kilogramme final paper would result. By using further mineral oil-containing additives, the concentration in the paper can increase. However, only some chemical additives contain mineral oil constituents, and in most cases their proportion is in a range between 1% and 3% maximum related on the additive mass. 

Defoamers and deaerators are added to oil well cement slurries to prevent excessive foaming and air entrapment. They act by lowering the surface tension of the liquid phase, if introduced in very low amounts. They include lauryl alcohol, dibutylphthalate, and some silicone compounds, such as polydimethyl siloxane. 

Major suppliers of defoamers and deaerating agents are American Ingredients Co., Harwick Chemical Corp., Wacker Silicones Corp., and Witco Corp. 

Chemical deaerators permit steady and prolonged deaeration by triggering bubble coalescence. This is achieved by means of hydrophilic emulsion particles, which penetrate the contaminated gas bubble surfaces, thereby facilitating their coalescence (Fig. 3.23). The difference in mechanism between deaeration by both thermomechanical and chemical means give the best results. The suitability of a defoamer and deaerator for certain mill conditions depends first on the hydro-phobicity or hydrophilicity of its components. This means that a very hydrophobic product is a good foam killer and a more hydrophibc one is an efficient deaerator. 

Defoamers and deaerators are derived from hydrocarbons that contain substituted polar groups. The active substances contained in products suppbed in the form of 25-30% aqueous emulsions are mainly higher fatty alcohols, fatty acids, and fatty add esters and their ethoxylates (Table 3.9). They may contain anionic or nonionic emulsifiers. The active substances contained in so-called oil-type defoamers are mainly fatty alcohol ethoxylates, fatty acid ethoxylates or mixtures of fatty alcohols. They can also contain emulsifiers in order to aid dispersion. It is important to note that the term oil-type defoamer refers to the oily consistency of this group of products, and has nothing to do with the use of mineral oil as an active substance. Emulsion-type defoamers account for half of the worldwide consumption of defoamers and deaerators, expressed as soHds. Synthetic oils represent 40% and mineral oils 10%. It seems that mineral oils are no longer in use in Europe. 

Uses Defoamer and deaerating agent for the wet treatment of PES and PES in blends and on the other type of n. fibers Features Silicone-free, shear stable... 

Uses Defoamer and deaerator for nonaq, systems, esp. flow coat paints for furniture based on nitrocellulose, acid curing systems Features Silicone-free... 

Uses Defoamer and deaerator for pulp and paper industry, paper and board stock, wastewater effluent, coating formulations, production of PVA-dispersions, deink-ing carrier for oil-based defoamers min. oil replacement base for emulsion-type defoamers defoamer in food-contact paper/paperboard Features Emulsifiable... 

To act as an effective defoamer or deaerator, the surface tension of the product has to be lower than that of the foaming liquid. The product must disperse uniformly and quickly and not be soluble into the water phase. Other factors that contribute to a product s efficacy are ... 

To address machine performance and paper quality issues, alternative chanis-tries are continuously being evaluated and proven within the industry. Present technology inclndes prodncts with chemistries such as synthetic alcohols, hydro-phobic wax particulates, and synthetic esters. Chemical defoamer formulations containing emnlsifiable combinations of hydrocarbons, alcohols, fatty acids, and various surface active agents are effective foam suppressors and deaerators. 

Chem. Descrip. Ethyi ether deriv. of fatty acid Uses Defoamer, deaerator for pigment siurries, coating coiors in paper coatings, and surf, sizing preps. defoamer, stock deaerator in papermaking... 

Silicone oils show some outstanding properties such as high surface activity, high thermo- and UV resistance, and low toxicity. Pure oils are also known to be used as plasticizers for silicone elastomers, as heat-resistant oils in transformers, and as raw material for deaerators, defoamers, and release agents for rubbers and fibers. 

Uses Size-protective emulsion defoamer for deaerating matter and destroying foam in paper industry... 

Uses Defoamer, antifoam and deaeration agent for unsat. polyesters, epoxies, and... 

Uses Emuision defoamer for deaeration and foam-prevention in size press... 

Because of the deaeration character of INTEX DEFOAMER 41 it is extremely effective in package dyeing and promotes the sinking of carpet. INTEX DEFOAMER 41 is nonionically emulsified making it compatible with all dyestuffs and finishing chemicals. 

Defoamer Chemical additive to control foam and treat existing entrained air problems Deaerator/antifoam Chemical additive to prevent build-up of entrained air EBS Ethylenebis(stearamide) wax, very hydrophobic defoamer component Silicone The most hydrophobic component used in defoamer formulations, may also be identified as siloxane technology... 

Most online systems, when used in the capacity of control rather than monitoring, establish a set-point for entrained air at a particular place in the papermaking system and allow the defoamer addition rates to change. In other words, the entrained air levels as measured by the online analyser are used to adjust the dose rates of the defoamer/deaerator additives. 

Most paper machines have measuring equipment installed to monitor free air in the white water or headbox. To successfully control the defoamer/deaerator dosage, free and dissolved gas need to measured. The Miitek GAS-60 Gas Analyzer provides two measurement points as recommended for a stable control loop. The chanical deaerator is dosed based on the free or dissolved gas content in the white water. The free or dissolved gas content of the headbox allows supervision of the mechanical deaerator, monitors leaking pumps and pinpoints other disturbing sources of air. 

The air content, which was 1.2% for the initial mortar composition, was not affected by the addition of the polymer dispersions. Since the mortar is free-flowing and has self-compacting properties, it is able to deaerate nearly completely. Moreover, it might be possible that the polymer dispersion already contains a defoaming agent, which could have led to a decrease in the air void content in the fresh mortar. 

Uses Foam control agent for water-thinned paints, coatings air release agent for polyester-resin spray and gel-coating operations deaerator in gluing operations food pkg. adhesives, coatings defoamer in food-contact paper coatings... 

Chem. Descrip. Organo-modified polysiloxane, contains fumed silica Uses Defoamer, deaerator for water-based airless spray-applied wood and furniture coatings food pkg. adhesives defoamer In food-contact... 

Uses Deaerating agent for med.-polar solv.-based systems, esp. NC-containing systems, vinyl paints, and acid-curing baking finishes (all -melamine and urea, acrylic-melamine, epoxy ester, high solids OEM finishes) food-contact coatings defoamer in food-contact paper/paperboard... 

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