This article addresses the strong market demand for pigment-stabilizing oligomers to obtain 100%-solids, VOC-free formulations. A new family of dendritic acrylate oligomers with different functionalities that address various stabilization mechanisms (pigment wetting, electrostatic and steric stabilization) will be discussed. Inks and coatings based on these oligomers are very fast curing and prone to substantially less oxygen inhibition. They demonstrate good adhesion to different substrates and possess excellent chemical and scratch resistance.
There are three main stages for dispersing pigments in paint, ink or coating solutions -wetting, grinding and stabilization of the pigment suspension. During the initial pigment wetting stage, the moisture on the surface of the pigment and air trapped within the pigment agglomerates. The extent of wetting depends on the viscosity of the solution and the surface tension of the pigments and dispersing media. In the grinding stage, pigment agglomerates are divided into smaller pieces and distributed uniformly. Dispersing agents that can adsorb onto the pigment surface are often used to avoid formation of flocculates and hence stabilize pigment dispersions. Electrostatic and steric stabilization are the two principal mechanisms for pigment stabilization. Polyphosphate and polycarboxylic acid derivatives are usually used as polyelectrolytes to provide electrostatic stabilization. In a solution with low dielectric constant, steric stabilization is the main type of stabilization. Additive or binder chains should be adsorped onto the surface of the pigments, so as not to allow flocculation of particles for effective steric stabilization.1