Water-based Paint Colorants

This Common Product focuses on low VOC water-based paint colorant systems. Water-based paint colorants are designed to tint interior and exterior base paints. Several different colorants may be mixed with a base paint to give a specific tint. Unlike universal colorants that can also be mixed with solvent-based alkyd paints, water-based colorants are designed to be used only with water-based paints. This specificity gives them several advantages over universal colorants, such as lower VOC content. It helps them avoid problems associated with universal colorants like surfactant bleeding, increased tack, and reduced blocking resistance. Addtionally, water-based colorants tend to affect the viscosity of the base paint less. 

Many of the additives in water-based colorants are similar to those found in water-based based paints. The level of pigment used in each colorant depends on its color strength, surface area, and the type of pigment. Pigments used in water-based paint colorants can be based on organic or inorganic chemical structures. Organic pigments tend to be brighter while inorganic pigments tend to be duller. Furthermore, the chemical structure of the pigment affects numerous physical properties of the final paint such as its resistance to weather and chemicals. The type of pigment can also affect both type and amount of additives added to specific colorants. For instance, titanium dioxide can promote the photodegradation of organic pigments. Similarly, some dispersants can be used on both organic and inorganic pigments, but a higher concentration is required for an organic pigment, and even higher concentration may be required for a black pigment. Despite the differences in formulation, additives were identified as common among the different types of pigments surveyed for this Common Product. 

In order to mix pigments with the base paint, a wetting agent is typically required in both the base paint and the colorant. Wetting agents are additives that are designed to lower the surface tension of the liquids that the solid pigment particles mix with. These surfactants can be based on several different types of chemistry. While the paint industry is moving away from the use of alkylphenol ethoxylates (APEs, or APEOs), fluorinated wetting agents are available for use with low-VOC water-based paints that aim to both reduce the amount of wetting agent required and remove the need for a wetting agent at the letdown phase of production in which the colorant is diluted. Little disclosure is available on the chemical composition of these surfactants. An additional concern is that low levels of polychlorinated biphenyls (PCBs), byproducts of pigment production, have been measured in a number of different paint colorants.