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Handling of powders, such as dosing, conveying or packing, is everyday’s business in the chemical industry. However, badly flowing or caking powders can cause various problems in production and — even worse — undesirable variations in quality. Other processes require accurate dosing of liquids into a powdery formulation. However, dispersing a liquid homogeneously into a powder is often a challenge. In these cases it is advantageous to convert the liquid into a powder, allowing a much more precise dosing and homogeneous distribution.
SIPERNAT® and AEROSIL® products facilitate all these processing steps significantly, as they help to ensure flowability of powders, minimize caking, or offer the possibility of converting viscous liquids into free flowing powders.
SIPERNAT® and AEROSIL® products improve the flowability of powders and reduce their caking tendency by enveloping the powder particles, spacing them apart, and thus reducing the cohesive forces. Furthermore, due to their high absorption capacity, they can absorb traces of liquid which are present on the surface of powder particles. Hydrophobic silica grades act very efficient because they tend to float on water-based moisture films keeping particles apart. This improves the flowability further, because any liquid present tends to glue the powder particles together. Several factors, such as the nature of the powder, dosage, order of addition of the ingredients, and applied shear forces, have a crucial influence on the final result and need to be considered when choosing the most suitable grade of SIPERNAT® precipitated silica or AEROSIL® fumed silica.
Converting highly viscous liquids or pasty substances into free flowing powders with SIPERNAT® precipitated silica greatly improves the handling and dosing characteristics. In the industry these absorbates often are referred to as “dry liquids”. Free flowing and non-dusting absorbates can be produced with the right silica grade to be chosen. The flow and dust characteristics of the final product are defined by the flow properties of the carrier silica. Here the particle size distribution of the carrier is important. A coarser particle size generally corresponds to better flowability and lower dust of the resulting product. However, there are some applications that require fine carrier particles, e.g. if an excellent dispersibility of absorbates in further processing steps is needed. Special SIPERNAT® and AEROSIL® grades are designed to fulfill that requirement. The amount of liquid that can be absorbed is given by the absorption capacity of the corresponding silica grade. Evonik offers a wide range of SIPERNAT® types to achieve the optimum result for any dry liquid.
Detailed information can be found in the brochures TI 1360 “SIPERNAT® and AEROSIL® as an Essential in Industrial Powder Technology” and TI 1213 “Specialty Silica as Flow Aid, Anticaking Agent and Carrier Substance Recommended Mixing Procedures for Powders and Granulates”
The following tables give some examples for the versatile applications of SIPERNAT® and AEROSIL® as flow aid and carrier substance.
Recommended type of SIPERNAT® or AEROSIL®
SIPERNAT® D17, SIPERNAT® 50S, SIPERNAT® 22S, AEROSIL® R 972
SIPERNAT® 22S, SIPERNAT® 360, SIPERNAT® D17 AEROSIL® 200, AEROSIL® R 972
Fire extinguishing powder
SIPERNAT® D17, SIPERNAT® D10, AEROSIL® R 974, AEROSIL® R 812
SIPERNAT® 22S, SIPERNAT® 50S, SIPERNAT® D17, AEROSIL® 200
SIPERNAT® 22S, SIPERNAT® D17, AEROSIL® R 972, SIPERNAT® 50S
SIPERNAT® D17, SIPERNAT® 22S, AEROSIL® 200, AEROSIL® R 974
SIPERNAT® 22S, SIPERNAT® 50, SIPERNAT® 50S
Recommended type of SIPERNAT®
SIPERNAT® 22, SIPERNAT® 33, SIPERNAT® 2200, SIPERNAT® 50
SIPERNAT® 22, SIPERNAT® 33, SIPERNAT® 2200
SIPERNAT® 22, SIPERNAT® 33, SIPERNAT® 2200, SIPERNAT® 50, SIPERNAT® 50 S
SIPERNAT® 22, SIPERNAT® 33, SIPERNAT® 50, SIPERNAT® 22LS, SIPERNAT® 500 LS
SIPERNAT® and AEROSIL® in Technical Powders
Technical Information 1213: Specialty silica as flow aid, anticaking agent and carrier substance
Technical Information 1360: SIPERNAT® and AEROSIL® - an Essential in Industrial Powder Technology
Technical Information 1413: SIPERNAT® specialty silica and AEROSIL® fumed silica for fire extinguishing powders