Development of a solvent selection guide for CO2 spray coating

•Acrylic resin-solvent paint formulations studied for CO2 spray coating.•Precipitation pressures for solutions with supercritical CO2.•Resin precipitation begins at about δmixture of 17 MPa0.5.•Paint formulations with acrylic resin should have δmixture >17 MPa0.5.

The use of CO2 for spray coating is a promising technique for volatile organic compound reduction in the paint industry. However, the polymer precipitation might be induced by the addition of CO2 into solvent, since CO2 is a poor solvent for most polymer solutions. In this work, a solvent selection guide for CO2 spray coating is proposed based on the solubility parameter from the viewpoint of avoiding the polymer precipitation. The precipitation tests were carried out for polymer (acrylic resin) + solvent (eight kinds) + CO2 systems. The solubilities of CO2 in the polymer + solvent (diethyl ketone, butanol, and methanol) varied from 7 to 33 wt.% CO2 at 40 °C for pressures from 0.9 to 6.4 MPa. It was found that the solubility parameter of the mixture at the precipitation point had similar values that are due to dissolution of the CO2 in the solution.

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