Application of hydroxypropyl cyclodextrin in thickeners for aqueous systems

Thickeners are rheology modifiers for paints and coatings. They can improve the flow and application properties of coatings, enhance thixotropy, and overcome defects such as sagging and settling. Thickeners are widely used in water-based coatings, adhesives, textile printing and dyeing pastes, inks, and the thickening of synthetic or natural emulsions. 
        Cyclodextrins and cyclodextrin derivatives (hydroxypropyl cyclodextrin) are used as thickeners in aqueous systems. They can eliminate the need for organic cosolvents and reduce the viscosity of associative thickeners. This not only addresses environmental safety and health concerns but also improves formulation performance. Because cyclodextrins can complex the hydrophobic residues on modified thickeners, they reduce the viscosity of the thickener, making it easier to use and handle. On the other hand, when a thickener containing cyclodextrin is added to a quasi-thickening aqueous system (such as an emulsion), substances with strong affinity for cyclodextrin (such as surfactants) can displace the hydrophobic residues on the thickener from the cyclodextrin, restoring the thickening function of the thickener. Therefore, the viscosity-suppressing function of cyclodextrin can be reversed when needed. Cyclodextrin derivatives have good solubility in water, allowing hydrophobic modified associative thickeners to be easily added to aqueous systems. When the paint and coating formulation contains colorants or surfactants, cyclodextrin can reduce the viscosity reduction and coloring difficulties of associative thickeners in the formulation, improve the efficiency of the associative thickener itself, and reduce the amount of thickener used. Cyclodextrin can also reduce the formation of foam in latex paints. When substances with affinity for cyclodextrin (such as surfactants) are present or added to the formulation, they can competitively form inclusion complexes with cyclodextrin, releasing the cyclodextrin-associated thickener and restoring the viscosity of the thickener.