The Particles form Gas Saturated Solutions process produces particles by spraying gas saturated solutions. A substance is melted, mixed with the dense gas and then expanded via a nozzle into a spray tower. The dense gas dissolves partly in the melt and reduces the viscosity. After the expansion the solubility is immediately reduced and the volume increase of the disappearing gas causes the liquid to disintegrate into tiny droplets. Due to the Joule- Thomson effect the gas cools down and consequently the droplets solidify almost immediately. The powder product is collected on the bottom of the spray tower. Finer particles are removed from the gas in a cyclone or filter. The process was patented under patent number WO9521688.

Morphologies of the particles depend on processing parameters like pressure, temperature, mass flow and gas to product ratio. Spheres, porous spheres, porous particles, micro-foams or fibers can be generated.

Apart from powders from pure substances also composites can be produced. In this case two vessels are used for the raw materials. In the first vessel the shell material (e.g. a polymer, fat or wax) is melted. The second vessel contains the liquid substance. Both materials are pressurized and mixed with supercritical CO₂.

Both materials are pressurized and mixed with supercritical CO₂ in the static mixer. Micro droplets of the liquid substance are formed in the molten encapsulating material. The emulsion is expanded through a nozzle into a spraying tower and forms fine droplets. Due to the Joule-Thomson effect the gas is cooling down rapidly and withdraws heat from the sprayed substances, so that the shell material solidifies. Depending on processing parameters open or closed composites are formed together with the liquid.

Powders can also be generated from two substances, which are solid at ambient temperature. In this case both have to be melted, pressurized, mixed with supercritical CO₂ and sprayed. In this way e.g. immiscible melts or reactive blends can be pulverized.

Process are low gas consumption (normally 0,1 - 2 kg gas/kg powder), inert atmosphere and low thermal stress. Spray towers are relatively small and scale-up can easily be realized based on our experience. Particles form Gas Saturated Solutions is applicable for a multitude of substances including low melting, high viscous and reactive compounds. The powders have tailor-made properties with adjustable morphology (bulk density 90 kg/m³ - 600 kg/m³) and particle size (500 nm to 1000 µm). 

Applications

Particles form Gas Saturated Solutions is a high pressure spraying process used to generate

• powders from pure substances, which are melted before spraying
• open and closed composites (e.g. encapsulation of liquids in shell materials like waxes or fats)
• powders from blends of immiscible melts
• reactive blends in powder formpowder coatings

Examples are powders produced from

• emulsifiers
• vitamins, antioxidants and fragrances
• fats and fat derivatives
• pharmaceuticals
• polymers

Controlled release properties can be achieved by using appropriate core and shell materials