Rheological Additives for Crop Protection - Elementis Specialties

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ELEMENTIS SPECIALTIES Rheological Additives Aqueous-Phase Aqueous-Phase Thickeners Thickeners 6 ELEMENTIS Specialties rheological additives can be broardly divided into thickeners for aqueous and non-aqueous systems. Clay and polymer based additives provide the desired flow control to water, oils or solvents to stabilise formulations. BENTONE BENTONE ® Hydrophilic Hydrophilic Hydrophilic Clays Clays BENTONE ® MA, EW and LT additives are produces from hectorite clay. Hectorite is a natural material and is the preferred clay for aqueous systems. It offers high swelling and suspension efficiency. Hectorite has a low iron content - important in the presence of iron-sensitive actives. Its inorganic nature provides thermostable flow control. BENTONE ® MA and EW additives form gels by producing an open, 3-dimensional network of the individual clay platelets as shown in Figure 5. BENTONE ® LT forms a similar network, but it is strengthened by the presence of a special cellulose, greatly enhancing stability and thickening characteristics. BENTONE ® LT is specially modified to be stable over a broader range, pH 3-11, and is the least sensitive to electrolytes. The range of ELEMENTIS Specialties products meeting EPA requirements can be requested from our regulatory department. Non-ionic surfactants, if they are highly ethoxylated, can adsorb onto the clay surface. This rarely causes problems either in flow control or activity of the formulation. Anionic surfactants can act as dispersing agents and weaken the gel structure. Alternatives that eliminate or minimise any problems can normally be found. However, cationic surfactants interact strongly and should be avoided. BENTONE® hydrophilic clays are used alone or in combination with other thickeners. Their use with xanthan gum and other polysaccharides is particularly effective in controlling suspension.
Fig 4 ELEMENTIS SPECIALTIES Rheology Additives Open Open flocculated flocculated gel gel network Incorporation Incorporation Hydrophilic Hydrophilic Hydrophilic Clays Clays Wetting Wetting - - Medium- to to high-shear mixing mixing - - Add clay clay to to water before before before addition addition of of other ingredients ingredients ingredients - - Disperse at at moderate pH Shear Shear - - Low shear shear shear (15 (>15 ms ms -1 ) .. ..= .. = = Shorter mixing mixing mixing time time time (10 (10 - - - 15 15 mins mins) mins Time Time - - 10 Minutes hydration hydration before before adding adding other other ingredients ingredients ingredients Heat Heat - - - Water at at up to to 60°C (140°F) reduces the the hydration hydration time, but is is not not a necessity necessity It It is important important to to have only only clean clean water water present present at at the dispersion dispersion stage. stage. stage. Surfactants Surfactants or electrolytes electrolytes should should should not not be added added added until until dispersion dispersion is is complete complete 7
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