Gas antisolvent fractionation of semicrystalline and amorphous poly(lactic acid) using compressed CO2

Preparation of phthalocyanine green nano pigment using supercritical CO2 gas antisolvent (GAS): experimental and modeling

Phthalocyanine green nano pigment was prepared using supercritical gas antisolvent (GAS) process based on the SC-CO₂ method. Thermodynamic models were developed to study the volume expansion and operating conditions of the GAS process. Peng-Robinson EoS were applied for binary (CO₂ and DMSO) and ternary (CO₂, DMSO, and pigment) systems. A Box-Behnken experimental design was used to optimize the process. Influences of temperature (308, 318 and 328 K), pressure (10, 15 and 20 MPa) and solute concentration (10, 40 and 70 mg/mL) were studied on the particles size and their morphology. The fine particles produced were characterized by SEM, DLS, XRD, FTIR and DSC. Experimental results showed a great reduction in size of pigment particles in comparison to the original particles. The mean particle sizes of nanoparticles were obtained to 27.1 nm after GAS based on SC-CO₂ method.

Separation processes for organic molecules using SCF Technologies

Supercritical fluids have been applied for many years for the separation of solutes from solids or solute mixtures in both exploratory and industrial applications. In the pharmaceutical industry the generation of pure solid states without impurities is important as the presence of impurities can result in a change in chemical properties or lead to physical instability. The literature on the separation and purification of solutes from solid matrices and solute mixtures using supercritical fluids, with the main emphasis on pharmaceutically important molecules, is reviewed in this article. Also discussed is the application of supercritical fluids in the control of process impurities such as chemical intermediates and residual solvent and in polymorphic control and chiral resolution. As the generation of organic molecules of pharmaceutical interest with high purity is important in pharmaceuticals this review additionally provides a brief overview of highly selective chemical reactions in supercritical fluids.

Plasticization and spraying of poly (DL-lactic acid) using supercritical carbon dioxide: control of particle size

Exposure of poly(DL-lactic acid) (PDLLA), and related polymers, to supercritical CO2 (scCO2) at or below, physiological temperatures leads to very effective plasticization and liquefying of the polymers. The phenomenon arises from the high solubility and interaction of the scCO2 in the polymer. Under these unique conditions, temperature and solvent labile molecules can be mixed efficiently into the liquefied polymer. This liquefied polymer/drug/CO2 mixture can then be sprayed into a collecting chamber, and during this process particles of drug-loaded polymer are formed. This process is very different from rapid expansion and antisolvent based techniques that have been previously reported. In this article, we describe a method of controlling particle size during the spray process by introducing a backpressure of N2 in the collecting chamber. This backpressure dynamically regulates the loss of CO2 from the issuing polymer/CO2 mixture, leading to control over sprayed particle size. In situ observation of the viscosity of the plasticized polymer indicates that a backpressure of 68 bar or greater is necessary to ensure the production of fine particles. The influences of backpressure and saturation temperature on particle size for the sprayed products are discussed in terms of observed PDLLA/CO2 mixture viscosities.