Novel Pigment Stabilizing Dendritic Oligomers

There are three main stages for dispersion of pigments in paint, ink or coating solutions; pigment wetting, grinding, and stabilization of pigments suspension. During the initial pigment wetting stage, the moisture on the surface of pigments and air trapped within pigment agglomerates.

Extent of wetting depends on viscosity of the solution and surface tension of pigments and dispersing media. In grinding stage, pigment agglomerates are divided into smaller pieces and distributed uniformly. Dispersing agents that can adsorb on to 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 on to the surface of pigments and do not allow flocculation of particles for effective steric stabilization.

Dendritic oligomers are highly branched sterically hindered oligomers. Various chemistries including polyurethane (meth)acrylates,2 aminoacrylates,3 and thioacrylates4 are reported in literature. Of these, thioacrylate dendritic oligomers are special interest to us due to their exceptional mechanical and physical properties in hard, protective coatings. They exhibit very good chemical and high temperature resistance as well as excellent adhesion properties to metal, glass and variety of plastics. This study focuses on the pigment stabilization properties of the new dendritic thioacrylate oligomers.