| Résumé : |
The impact of rheology modifiers on paint and coatings formulations has been, and continues to be immeasurable. This is especial ly true in architectural coatings as the choice of rheology modifier in most cases, determines the paint and film properties. Rheology modifiers used in the architectural paints include cellulose-based (water soluble polymers - HEC), poly-acryl ic-based (ASE and HASE) and ether-urethane polymer/polyether-based (H EU R/PEPO). Cellulose-based additives have been used to thicken paints and coatings for well over five decades. This class of rheology modifiers is relatively easy to formulate with without creating stability issues observed in the other classes of rheology modifiers. The thickening mechanism is by volume exclusion, resulting in the occurrence of flocculation — both pigment and latex - of the paint system. This may result in poor wet and dry hide film properties, as well as affect other paint film characteristics. However, the paint does not exhibit viscosity loss on tinting and colour stabilityy issues as is observed with the other type of thickeners. The poly-acrylic thickener was an attempt to provide the paint manufacturer with a liquid alternative to the cellulose-based rheology modifiers. The initial iteration was the alkali soluble emulsion, ASE, which was supplied as a low pH liquid to be incorporated as a dilute solution (1:1 with water) into the let-down phase of the paint batch making process. The thickening mechanism was similar to that of HEC. Their main advantages were ease of handl ing as well as the el imination of dust. Application properties such as spatter resistance, levelling, etc. were observed to be similar to, if not better than, paints thickened with HEC. |
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Waterborne rheology modifiers : Improving thickening efficiency in PAINTINDIA, Vol. LXXII, N° 9 (09/2022)
