Spray emulsions

Sprays. Aerosol spray emulsions are of the water-in-oil type. The preferred propellant is a hydrocarbon or mixed hydrocarbon—hydrofluorocarbon. About 25 to 30% propellent, miscible with the oil, remains in the external phase of the emulsion. When this system is dispensed, the propellant vaporizes, leaving behind droplets of the w/o emulsion (Fig. 2b). A vapor tap valve, which tends to produce finely dispersed particles, is employed. Because the propellant and the product concentrate tend to separate on standing, products formulated using this system, such as pesticides and room deodorants, must be shaken before use. 

The oils were applied in the form of an aqueous emulsion prepared according to the tank-mixture method. Most of the time it is possible to approach a given oil deposit by proper adjustment of the concentration of oil in the spray mixture. The volume basis was used for the concentration of oil in the spray emulsion. The ingredients were emulsified and agitated by means of a high speed homomixer (made by Eppenbach, Inc., Long Island City, N. Y.). 

The mean quantity of oil deposited, in micrograms per square centimeter for each lot of sprayed fruit, was determined colorimetrically according to a method developed by Riehl, Gunther, and Beier (22), Portions of the various oils were partially saturated with Oil Red 0. Dyed oil was used to prepare the spray emulsion applied to the fruit. It was shown that the concentrations of dye used were not toxic to the insects and did not affect the direct relationship of amount of deposit to mortality. 

Sensitization of Model Systems. Silver bromide sheet crystals can be sulfur-sensitized easily, and have been studied extensively (56-58). Evaporated silver halide layers and sprayed emulsions likewise can be sulfur-sensitized. 

Pearlman and associates (63) found that sprayed emulsions prepared from silver bromide could be sulfur-sensitized by conventional means, but the increase in sensitivity was only twofold. The increase for grains prepared with 99% AgBr plus 1% Agl, on the other hand, was tenfold. They did not detect a difference in structure between the pure bromide and the iodo-bromide grains. The response of equimolar chlorobromide grains to S-sensitization also was greater than that of the pure bromide. 

Han, Y.K., Yih, J.N., Chang, M.Y., Huang, W.Y., Ho, K.S., Hsieh, T.H., Lou, J.G., 2011. Facile synthesis of aqueous-dispersible nano-PEDOT PSS-co-MA core/shell colloids through spray emulsion polymerization. Macromol. Chem. Phys. 212,361-366. 

Applications include the following material systems powdered materials either dry or in suspensions continuous or pulsed droplet sprays, emulsions, and some solids in solids provided that the suspending medium is transparent. 

A prilling tower (height 4.5 m, diameter 1 m) was used for the production of solid particles from sprayed emulsions of all types. The two different types of commercial twin-fluid nozzle geometries introduced in Fig. 23.9 and Table 23.5 were used for the prilling investigations. The average temperature inside the tower was generally maintained at —10 or —35 °C for fat-based and water-based emulsions, respectively. Particles were collected from the tower bottom part and stored at room temperature (fat-based emulsion) or —20 °C (water-based emulsions) in a closed container. 

For this two-phase gas/liquid flow, the gas Weber number is introduced as the ratio between the applied relative kinetic energy (here by the relative velocity of the gas and the liquid (emulsion) phases) and the interfacial energy (restriction for interface deformation) of the sprayed emulsion. For the spraying process, two gas Weber numbers were defined (i) concerning the tertiary spray droplet (Wgg Nozzle)... 

In the previous sections, the impact of the material properties of emulsions and spray process parameters on the dispersion was described. It provided information about the dispersion of secondary droplet of DE, rather than the release of an encapsulated component. The release of functional components during spray processing may also be influenced by shear-induced diffusion and osmotic pressure. Therefore, an iron-salt (FeS04) encapsulated DE was sprayed and the retained amount of iron in the sprayed emulsion detected. Conductivity and Atomic Adsorption Spectroscopy (AAS) methods were used for measuring the concentration of iron. The retained amount of iron is defined as follows (23.15) ... 

Uses Excipient, coemulsifier, solubilizer, bioavailability enhancer, vehicle for pharmaceuticals (topicals, injectables, orals, nasals, sprays, emulsions, hard shell capsules, soft gel capsules), cosmetics, veterinary preps. cosurfaclant in microemulsions coemulsifier, penetrant for topical emulsions Features Hydrophilic... 

Emulsions. Aerosol emulsions (qv) may be oil in water (o/w), such as shaving creams, or water in oil (w/o), such as air fresheners and pohshes. These aerosols consist of active ingredients, an aqueous or nonaqueous vehicle, a surfactant, and a propellant, and can be emitted as a foam or as a spray. 

An emulsion system in which the propellant is in the external or continuous phase is shown in Figure 2b. As the Hquefied propellant vaporizes, it escapes direcdy into the atmosphere, leaving behind droplets of the formulation which are emitted as a wet spray. This system is typical of many water-based aerosols or w/o emulsions. 

Compounded Flavors. Liquid or dry blends of natural or synthetic flavor compounds are called compounded flavors. Most commercial preparations are available as water- and oil-soluble Hquids, spray-dried and plated powders, emulsions, and carbohydrate-, protein-, and fat-based pastes. Compounded flavors are used throughout the food industry in confections, baked goods, snack foods, carbonated beverages, and processed foods (53). 

In one extractor (FMC Inc.), the fmit is located between two cups having sharp-edged metal tubes at their base. The upper cup descends and the many fingers on each cup mesh to express the juice as the tubes cut holes in the top and bottom of the fmit. On further compression, the rag, seeds, and juice sacs are compressed into the bottom tube between the two plugs of peel. A piston moves up inside the bottom tube forcing the juice through perforations in the tube wall. A simultaneous water spray washes the peel oil expressed during extraction away from the peel as an oil—water emulsion the peel oil is recovered separately from the emulsion. 

Petroleum Oils. When satisfactorily stable kerosene—soap—water emulsions were produced in 1874, dormant (winter) oil sprays became widely used to control scale insects and mites (1). The first commercial emulsion or miscible oil was marketed in 1904 and by 1930 highly refined neutral or white oils, free from unsaturated hydrocarbons, acids, and highly volatile elements, were found to be safe when appHed to plant foHage, thus gready enlarging the area of usefulness of oil sprays (see Petroleum). 

Emulsives are solutions of toxicant in water-immiscible organic solvents, commonly at 15 ndash 50%, with a few percent of surface-active agent to promote emulsification, wetting, and spreading. The choice of solvent is predicated upon solvency, safety to plants and animals, volatility, flammabiUty, compatibihty, odor, and cost. The most commonly used solvents are kerosene, xylenes and related petroleum fractions, methyl isobutyl ketone, and amyl acetate. Water emulsion sprays from such emulsive concentrates are widely used in plant protection and for household insect control. 

DDT at 0.25—0.75% and dieldrin at 0.05% appHed during dry cleaning or by spraying fabrics with aqueous emulsions of equivalent strength were formerly used extensively as semipermanent fabric protectants. However, these are no longer used because of problems of environmental contamination. 

Classification of the many different encapsulation processes is usehil. Previous schemes employing the categories chemical or physical are unsatisfactory because many so-called chemical processes involve exclusively physical phenomena, whereas so-called physical processes can utilize chemical phenomena. An alternative approach is to classify all encapsulation processes as either Type A or Type B processes. Type A processes are defined as those in which capsule formation occurs entirely in a Hquid-filled stirred tank or tubular reactor. Emulsion and dispersion stabiUty play a key role in determining the success of such processes. Type B processes are processes in which capsule formation occurs because a coating is sprayed or deposited in some manner onto the surface of a Hquid or soHd core material dispersed in a gas phase or vacuum. This category also includes processes in which Hquid droplets containing core material are sprayed into a gas phase and subsequentiy solidified to produce microcapsules. Emulsion and dispersion stabilization can play a key role in the success of Type B processes also. 

The second step is to disperse the core material being encapsulated in the solution of shell material. The core material usually is a hydrophobic or water-knmiscible oil, although soHd powders have been encapsulated. A suitable emulsifier is used to aid formation of the dispersion or emulsion. In the case of oil core materials, the oil phase is typically reduced to a drop size of 1—3 p.m. Once a suitable dispersion or emulsion has been prepared, it is sprayed into a heated chamber. The small droplets produced have a high surface area and are rapidly converted by desolvation in the chamber to a fine powder. Residence time in the spray-drying chamber is 30 s or less. Inlet and outlet air temperatures are important process parameters as is relative humidity of the inlet air stream. 

The different types of furniture pohshes include hquid or paste solvent waxes, clear oil pohshes, emulsion oil pohshes, emulsion wax pohshes, and aerosol or spray pohshes (3). Nonwoven wipes impregnated with pohsh ingredients have been targeted at consumers who do not wish to expend the time to dust before polishing (11). Compilations of representative formulas are given in References 3, 4, 12, and 13. Paste waxes contain ca 25 wt % wax, the remainder being solvent. Clear oil pohshes contain 10—15 wt % oil and a small amount of wax, the rest being solvent. Aerosol or spray products may contain 2—5 wt % of a sihcone polymer, 1—3 wt % wax, 0—30 wt % hydrocarbon solvent, and ca 1 wt % emulsifier. The remainder is water. 

Water Dispersions. Polysulftde products are offered as aqueous dispersions (Thiokol WD-6). These are useful for applyiag protective coatings to line fuel tanks, and for concrete, wood, and ia some cases fabrics, felt, leather (qv), and paper (qv). It has been found that a stable emulsion can be made that contains both LP and manganese oxide curing agent. The emulsion can be thinned and appHed as a spray coating. After it is appHed, water evaporates and the LP cures to form a soHd mbber (13). 

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