They find application in the treatment of wastewater of any industrial activity and within production processes, especially in the agri-food and pharmaceutical sectors. Tropical test: 2 weeks at +54 ☌ (CIPAC 1 -MT 46.1.SNF’s range of defoamers consists of silicone, non-silicone, and water-based products. Some accelerated aging tests give a fast indication of the long term stability: However, the presence of a supernatant water layer on the surface is acceptable, provided only slight agitation is needed for the mixture to re-disperse. The commercial formulations should be stable for at least 2 years without any significant change of viscosity and without sedimentation or phase separation. The role of this additive is to avoid formation of foam during preparation, water dilution and field application. RHODOPOL, added after the mixing step, provides perfect long term storage stability in most cases. Monopropylene glycol or glycerine are the most commonly used antifreezes in the range of 50 to 80 g/l. According to the chemical nature of the active ingredient, the chemical nature of the hydrophobic part of the emulsifier has to be optimized, in order to generate the strongest affinity with the liquid to be emulsified, at around the same required HLB value. The required HLB to emulsify this active ingredient (example) is about 14 (it corresponds to the emulsion with the smallest particle size). The choice of a surfactant system depends on the polarity of the oil to be emulsified, the interactions which can be created between the oil phase and the surfactant system, the nature of the continuous phase. The strong adsorption of well chosen surfactants at the interface oil/water of the droplets generates repulsive forces (steric and/or electrostatic) in order to positively balance the attractive ones. After emulsification the dispersed droplets have an inherent tendency to flocculate as the result of the attractive Van der Waals and electrostatic forces. They assure the fluidity of the emulsion by developing strong repulsive forces hindering aggregation, flocculation or coalescence. To be efficient, surfactants need to be strongly adsorbed or solubilised at the interface oil/water. Improve compatibility with other formulations in a diluted state at the application rate. Provide steric and electrostatic stabilization to the micronized droplets against flocculation, aggregation or coalescence in a concentrated state, to guarantee the long term stability of emulsions in various storage conditions.įacilitate dispersion of the formulation during water dilution and stabilize the micronized droplets of the active ingredient in the diluted state. They act in the following way:ĭuring mixing, they allow the wetting and dispersion of the organic phase into the aqueous phase by reducing the oil/water interfacial tension. If necessary, adjust the viscosity value with a 2% water solution of RHODOPOL 23.Įmulsifiers are basic components in water based concentrated emulsions. The final viscosity, after degassing, can vary considerably depending on the components and the working process - it should be between 10 mPa.s (Brookfield 20 rpm) for long term stability. The use of an antifoam during the process is highly recommended to avoid the increase of viscosity due to air entrapment. Emulsifiers can be added to water or to actives and component mixed by a suitable stirrer (high speed mixing agitation) to achieve an average size of approx 1 µm. Manufacture description and structures of emulsions: role of emulsifiersĭifferent parameters are involved in the preparation of an emulsion the energy input, the temperature, the way of introduction of different ingredients and the rheology are important to obtain a long term stable emulsion. Stabilizing agent or buffer can be added when necessary. Small amount of solvent can be added to obtain a solution of the active ingredient. Active ingredients need to have a good chemical stability in water. Higher flash point, safer in transport and storageĬompatibility with water-based suspension concentratesĬoncentrated base in water for suspoemulsions (SE) formulationsĮmulsions in water are suitable for liquid active ingredients and also for low melting point actives which cannot be formulated under a suspension concentrate (SC) form. Reduction of the phytotoxicity, ecotoxicity and dermal toxicity The size of the dispersed droplets generally range from 0.5 to 2 µm.Įmulsions can be obtained by a low shear or high shear process and are usually stabilized by a thickening agent and/or hydro-colloids in order to ensure long term stability.ĮW formulations, when compared to EC formulations, offer: Emulsion in water (EW) results from the dispersion of a liquid or a low melting point active ingredient in a water continuous phase.
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