Bio-inspired conformational lipophilization of wood for scCO2-assisted colouring with disperse dyes

Recent advances in supercritical fluid dyeing

“…A comparison with a similar impregnation process conducted in acetone revealed that higher impregnation depth was obtained by using the supercritical solvent. 107 Recent research by Jaxel et al 108 exploited the above-cited results to investigate the feasibility of dyeing wood through supercritical carbon dioxide. The supercritical fluid coloration of wood could be of interest in the furniture industry to achieve a more efficient and environmentally compatible dyeing approach.…”

“…On the other hand, the principal constituents of woods are cellulose and hemicellulose, which are rich in hydroxyl groups that give rise to strong intra-and intermolecular hydrogen bonding that prevent the plasticising action of supercritical carbon dioxide. 108 According to this explanation, a second set of experiments was conducted by pretreating the wood samples with alkyl ketene dimer (AKD). AKD is a paper-sizing agent that is usually employed to impart hydrophobicity to paper; in this context it was selected to mimic the action of suberin in wood.…”

“…The results indicated the good plasticising and swelling action of AKD on wood samples, which were successfully dyed, even though the homogeneity of coloration was not satisfactory. 108 In the most recent publication by this research group, 109 the above-reported imperfect coloration of wood was ascribed to insufficient solubility of the employed dye in the supercritical solvent. For this reason, the authors proposed the synthesis of new anthraquinone dyes with long-chain alkyl substituents should result in increased supercritical carbon dioxide solubility.…”

“…Recent research by Jaxel et al 108 exploited the above‐cited results to investigate the feasibility of dyeing wood through supercritical carbon dioxide. The supercritical fluid coloration of wood could be of interest in the furniture industry to achieve a more efficient and environmentally compatible dyeing approach 109 .…”

“…The good coloration of cork was ascribed to the presence of suberin, an irregular macromolecular polyester present in the cork cell walls that could promote the diffusion of supercritical carbon dioxide in the solid substrate. On the other hand, the principal constituents of woods are cellulose and hemicellulose, which are rich in hydroxyl groups that give rise to strong intra‐ and intermolecular hydrogen bonding that prevent the plasticising action of supercritical carbon dioxide 108 . According to this explanation, a second set of experiments was conducted by pretreating the wood samples with alkyl ketene dimer (AKD).…”