Water resin emulsification

The emulsification method is primarily used for waterborne epoxy adhesive systems and is the focus of this section. The epoxy resin is made water-dispersible by partitioning the epoxy resin within a micelle, effectively separating the resin from the water. This emulsification can be achieved by a suitable surfactant. 

The surfactant selection determines the emulsion properties, such as stability, particle size, viscosity, and internal phase content. A correct balance between the hydrophobic and hydrophilic character of the emulsifier is necessary for minimizing the surfactant concentration at the resin-water interface. The surfactants used in resin emulsification can be ionic (in most cases anionic), nonionic, polymeric, or a combination of these. 

Most of mineral fillers can be easily incorporated into solvent-borne and water-borne (adding adequate surfactants and wetting agents) adhesives. Hydrocarbon resins, rosin, rosin ester, coumarone indene resins, and terpene resins can be directly added to solvent-borne adhesives. For latex adhesives, resin emulsification must be produced before addition. 

Uses Emulsifier, dispersant for paints/coatings, inks, universal colorant systems dispersant for color pastes, color cones., Ti02, extender pigments and stabilizer in latex paints emulsifier, emulsion stabilizer for resin emulsification Properties Amber liq, HLB 11.4 pH 3-6 (10% aq.) 100% act, 4% max. water Zetesap813P [Zschimmer Schwarz]... 

Orange shades are realized with lipophilic natural colorants like paprika oleo-resin, P-carotene, and canthaxanthin after previous emulsification to yield water-dispersible forms. Yellow shades can be achieved using turmeric as a water-soluble solution, but the solution is light sensitive. To maintain constant color, 3 to 6 ppm of P-carotene may be added. Stable brown coloration is obtained from caramel a concentrated syrup is easily incorporated, well flavored and stable in creams. ... 

The emulsification process is simple but must be carefully controlled. Epoxy resin is loaded into a high-speed disperser, and the surfactant is added. A defoamer is generally added to prevent excessive aeration, and high-shear mixing is employed. Water is then slowly added to the mixture. The system at this stage has the epoxy resin as the continuous phase and the water as the dispersed phase. As the water addition continues, the ratio of the dispersed phase to the continuous phase increases until a phase inversion occurs. The inversion occurs at about 65 percent volume ratio of dispersed to continuous phase and is accompanied by a rapid reduction in viscosity. Water addition is then continued until the desired solids concentration is achieved. Additional additives and modifiers can be incorporated into the formulation at this stage. 

Surface-active agents. Surface-active agents such as emulsifiers and surfactants play a very significant role in the stability of emulsions. They greatly extend the time of coalescence, and thus they stabilize the emulsions. Mechanisms by which the surface-active agents stabilize the emulsion are discussed in detail by Becher (19) and Coskuner 14). They form mechanically strong films at the oil-water interface that act as barriers to coalescence. The emulsion droplets are sterically stabilized by the asphaltene and resin fractions of the crude oil, and these can reduce interfacial tension in some systems even at very low concentrations (i7, 20). In situ emulsifiers are formed from the asphaltic and resinous materials found in crude oils combined with ions in the brine and insoluble dispersed fines that exist in the oil-brine system. Certain oil-soluble organic acids such as naphthenic, fatty, and aromatic acids contribute to emulsification 21). 

Several industrial systems involve emulsions, of which the following are worthy of mention. Food emulsions include mayonnaise, salad creams, deserts, and beverages, while personal care and cosmetics emulsions include hand creams, lotions, hair sprays, and sunscreens. Agrochemical emulsions include self-emulsifiable oils that produce emulsions on dilution with water, emulsion concentrates with water as the continuous phase, and crop oil sprays. Pharmaceutical emulsions include anaesthetics (O/W emulsions), hpid emulsions, and double and multiple emulsions, while paints may involve emulsions of alkyd resins and latex. Some dry-cleaning formulations may contain water droplets emulsified in the dry cleaning oil that is necessary to remove soils and clays, while bitumen emulsions are prepared stable in their containers but coalesce to form a uniform fihn of bitumen when apphed with road chippings. In the oil industry, many crude oils (e.g.. North sea oil) contain water droplets that must be removed by coalescence followed by separation. In oil slick dispersion, the oil spilled from tankers must be emulsified and then separated, while the emulsification of waste oils is an important process for pollution control. 

In the new process, other separation zones are added after the normal first separation zone. The heavy phase from the first zone is sent to a suipper and the vaporized solvent, steam, and fine mist particles are withdrawn from the top and are conveyed to the second separation zone. In the second separation zone, the stream consisting of solvent, steam, and mist particles flow through a circuitous path where it is contacted couniercurrently with a sU eam of light oil which scrubs the asphaltene and resin mist from the solvent. A portion of the light phase oil containing asphaltenes and resins is recycled to the second separation zone or it can be recycled to the first separation zone. The solvent and steam mixture leaving the second zone is conveyed to a solvent condenser and water separation zone. No emulsification problems are exp>erienced because the mist particles have been removed in the first separation zone. 

Emulsification Emulsification is considered the second most important weathering process after a marine spill by which water is dispersed into oil in the form of small droplets. The mechanism of water-in-oil emulsion formation is not yet fully understood, but it probably starts with sea energy forcing the entry of small water droplets, about 10 to 25 /rm in size, into the oil. Emulsions of many types contain about 70% water. In general, water-in-oil emulsion can be categorized into four types (1) unstable oil simply does not hold water (2) entrained water droplets are simply held in the oil by viscosity to form an unstable emulsion, and it breaks down into water and oil within minutes or a few hours at most (3) semistable or meso-stable the small droplets of water are stabilized to a certain extent by a combination of the viscosity of the oil and interfacial action of asphaltenes and resins. For this to happen, the asphaltenes or resin content of the oU must be at least 3% by weight. The viscosity of meso-stable emulsions is 20 to 80 times... 

Other water-borne coatings include water-soluble emulsions, dispersions, and latex resins. Water-soluble resins are rare because most resins derived from vegetable oils are insoluble in water. The true emulsions are based on the emulsification of the oil or alkyd through either the action of a surfactant or a resin that has a surfactantlike character. The alkyd emulsions are readily prepared and can be used for OEM coatings and architectural applications. The submicron size droplets are stabilized by the thickeners (El-Aasser Sudol, 2004 Landfester, 2005 Landfester et al., 2004 Tsavalas et al., 2004 Weissenborn Motiejauskaite, 2000a,b). In dispersions, the resin is a solid and is dispersed in water. The latex resin is usually vinyl acetate, styrene, acrylates, or methacrylates radically copolymerized in a micelle to form particles 0.1 pm in diameter (Bloom et al., 2005 Brister et al., 2000 Jiratumnukul Van De Mark, 2000 Thames et al., 2005). 

OTHER COMMENTS used as a solvent for nitrocellulose resins, spray lacquers, quickdrying lacquers, varnishes, enamels, varnish removers, and dry-cleaning compounds mutual solvent for soluble mineral oils to hold soap in solution, and to improve emulsification use to make acetate esters as well as phthalate and stearate plasticizers preferred coupling agent for many water-based coatings. 

There has always been a desire for water-soluble epoxy resin systems. Although epoxy resins were introduced a good many years ago, all attempts at water systems have met with general failure. The investigations into epoxy systems as emulsions for use with concrete have been roughly divided into three general classifications. The first attempts were in the emulsification of the epoxy resins themselves. The problems and failures in this approach may be generalized as follows ... 

In most cases, anionic water-soluble polymers such as poly(styrene-maleic anhydride), polyacrylic acid, etc., are apphed. These kinds of emulsifiers can influence the microcapsule preparation, mean particle size, and particle size distribution. By emulsification, an electric double layer generates on the dispersed phase. Then the electrostatic interactions between the protonated amino resin prepolymer and the negatively charged orgaific phase can act as a driving force, which enable the wall material polycondensate on the surface of the oil droplets but not throughout the whole water phase. ... 

Emulsions made by mechanical means, using external surfactants and colloids, are not popular in paints today, being formerly used in oil-bound distempers, based on drying oil emulsions. Nowadays, mechanical emulsification is generally used with resins which are internally modified to emulsify in water, e.g. in electrodeposition paints (see p. 109). 

The drying oil fatty acid chains can be partially maleinized to permit emulsification when the carboxyls have been partially neutralized and the resin dispersed in water/solvent mixtures. These waterborne epoxyesters can be used as binders for anodic electrodeposition primers (see p. 109). 

The two materials are mixed together and the tertiary amino groups in the modified epoxy resin are partially neutralized with acetic acid before emulsification in water. 

Another common approach to water-based coating formulations is post-emulsification of a polymer in water. Several condensation polymers, e.g. alkyds, i.e. fatty-acid-modified polyesters, polyurethanes and epoxy resins, have been made into dispersions by the use of a suitable emulsifier and application of high shear. For instance, long oil alkyd resins of the type used in white-spirit-based formulations have been successfully emulsified by using nonionic surfactants such as fatty alcohol ethoxylates, alkylphenol ethoxylates or fatty acid monoethanolamide ethoxylates. Neutralization of alkyd carboxylic groups helps in producing small emulsion droplets and with the proper choice of surfactant, droplet diameters of less than 1 pm can be obtained. Such dispersions are sufficiently stable for most applications. 

Silica nanoparticles could also be encapsulated with an epoxy resin to produce water-borne nanocomposite dispersions by using the phase-inversion emulsification technique [98]. Microscopy results indicated that all the siHca nanoparticles were encapsulated within the composites and uniformly dispersed therein. 

Resins are incorporated in Neoprene latex as solvent-cut emulsions, solventless pebble-milled dispersions, or sometimes as solvent-free emulsions prepared using invert emulsification techniques. In the latter case a resin with a melting point of 80°C (176 F) or lower is melted. Water and surfactants are added to the molten resin and the temperature of the mixture is decreased. Upon reaching a certain temperature, known as the phase inversion temperature, the water in molten resin emulsion spontaneously inverts to form a resin in water emulsion suitable for use in latex adhesives. A resin dispersion which can be prepared in this manner is shown in Table 16. This particular resin dispersion can be used to produce adhesives with moderate hot strength and good open time using the following recipe ... 

Resin-water emulsions can be produced by the post-reaction emulsification of a condensation or addition polymer, by the use of surfactants or emulsifiers to form an oil-in-water emulsion of the polymer in the aqueous phase. This is simply a method of obtaining a polymer in an aqueous medium. This type of emulsion is different from a tme emulsion polymer made by the process of emulsion polymerisation. 

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