Rheology Modifiers
CAVASOL® cyclodextrins to produce VOC-free Rheology Modifiers
Rheology modifiers control the viscosity and flow characteristics of the product in coatings and emulsion formulations. They prevent the paint from being as runny as water, from splashing everywhere during application by brush or roller, and from flowing unevenly before it has dried. Rheology modifiers can reduce dripping and splattering of the drying paint during application and can prevent pigment sedimentation in the can during transport and storage.
There are two main classes of rheology modifiers:
- Inorganics (clays, silica)
- Organics (natural carbohydrate polymers and synthetic polymers)
Associative thickeners are a class of synthetic polymers. They contain hydrophobically-modified ethylene oxide-based urethanes or HEURs and thicken by building networks through hydrophobic interactions of the end-groups with themselves and the latex particles in paint.
CAVASOL® cyclodextrins are a group of highly water-soluble, chemically modified cyclodextrins. Cyclodextrins are a well-known group of natural carbohydrates that, due to their novel cyclic structure, can act as the host in a host-guest complex. This encapsulation product, frequently also called an ‘inclusion complex’ or a ‘molecular encapsulation’, undergoes a reversible, equilibrium-controlled process in water, releasing the hydrophobic guest.
Low-Viscosity, VOC-Free, Aqueous HEUR Formulations
It is known that HEUR rheology modifiers can be dissolved in water containing CAVAMAX® and CAVASOL® cyclodextrins to give a low-viscosity, pumpable, VOC-free, aqueous solution of HEUR. When the solution is incorporated into the finished paint, the reduction in viscosity is fully reversed, due to the presence of surfactants already in the paint.
The aqueous CAVASOL® HEUR solutions can be incorporated into the formulated paint to provide the required rheological control, without any detrimental effect on performance, as confirmed by industry standard tests and practices in respect of efficiency, flow, gloss, colorant, and heat stability. *
*According to patent US 5376709A Lau et al.