Estimating Hansen solubility parameters of organic pigments by group contribution methods

The Hansen solubility parameters (HSP) are frequently used for solvent selection and characterization of polymers, and are directly related to the suspension behavior of pigments in solvent mixtures. The performance of currently available group contribution (GC) methods for HSP were evaluated and found to be insufficient for computer-aided product design (CAPD) of paints and coatings. A revised and, for this purpose, improved GC method is presented for estimating HSP of organic compounds, intended for organic pigments. Due to the significant limitations of GC methods, an uncertainty analysis and parameter confidence intervals are provided in order to better quantify the estimation accuracy of the proposed approach. Compared to other applicable GC methods, the prediction error is reduced significantly with average absolute errors of 0.45 MPa^1/2, 1.35 MPa^1/2, and 1.09 MPa^1/2 for the partial dispersion (δ_D), polar (δ_P) and hydrogen-bonding (δ_H) solubility parameters respectively for a database of 1106 compounds. The performance for organic pigments is comparable to the overall method performance, with higher average errors for δ_D and lower average errors for δ_P and δ_H.