Spray-polymerization

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The vision of the SPP Process Spray is the evaluation of the interdependency of the fluid properties, spraying parameters and the properties of the synthesized powder. The process of spray-polymerization synthesizes a polymeric solid. The synthesis of the polymer form the monomer starts already within the spraying nozzle and is continued within the drop after atomization. The solid is formed due the reaction progress as well as due to the drying of the carrier solvent. In a one-step-process the process strategy combines the synthesis of the polymer with the design of the particle properties, which typically needs at least two independent steps. The spray polymerization is supposed to allow the synthesis of polymeric particles in the size range of 5-100 µm with specified particle properties. A special technical challenge here is the integrated crosslinking of the polymer. The state of technology has only limited options to produce defined polymeric particles in the size range from 1-50 µm. Emulsion- and suspension polymerization lead to compact dense spherical particles. The top-down approach by dry fine milling has severe problems in reaching a particle size below about 50 µm due to the elastic properties of the polymer material. A patent review shows a prove of principle for spray polymerization, but no quantitative data related to process design. The kinetic of the combined polymerization reaction and drying process is the main focus of experimental work in lab and pilot scale, it goes along with a theoretical description of the reaction. The technical realization also needs the development of a specialized technical components to control the start phase of the reaction. The layout of these components is strongly supported by lab scale characterization of the polymerization within an analytical rheometer, providing the relation of reaction progress and viscosity. The latter is the key property to ensure the application of the atomization process. The materials used are (neutralized) acrylic acid as monomer, which leads to particles of poly- -acrylic-acid sodium salt. This salt is synthezied either as linear polymer or as crosslinked gel. Furthermore it is also evaluated whether it is possible to crosslink existing polymer chains during spray polymerization.