Paint Ink Additives

Pigment stabilization by steric hindrance

When dispersing pigments, in particular organic pigments, one often encounters problems such as flocculation, insufficient colour or transparency, poor rheological behaviour or bad stability. These issues arise along every step of the coatings life cycle from production and storage through to the end-use performance of the film. The dispersing of solid pigments or fillers into the liquid phase of binder solutions is an important step in paint and coatings production influencing optical properties like gloss and colour strength. Dispersion control additives are used to improve and accelerate the dispersion process and to stabilize the dispersion during storage.

High molecular weight wetting and dispersing agents

They are built of linear or branched polyacrylate or polyurethane structures with a molecular weight between 5,000 g/mol - 30,000 g/mol and have special groups which have high affinity towards specific sites on the pigment surface. These are called anchoring groups, and are built in at strategic points on the polymer backbone.

Mode of action

Anchoring groups enable strong interaction between the dispersion control additive and the pigment surface. This interaction is much stronger compared to the anchoring mechanism of the conventional low molecular weight types. Because these dispersion control additives have multiple adsorptions points, they are therefore connected to numerous sites on the surface of the pigment particles. The remaining parts of the dispersion control additive act as a steric barrier to the surroundings by stretching into the liquid phase and assuring an effective steric hindrance preventing flocculation.

Pigment stabilization by controlled flocculation

The dispersing of solid pigments or fillers into the liquid phase of binder solutions is an important step in paint and coatings production influencing optical properties like gloss and colour strength. Dispersion control additives are used to improve and accelerate the dispersion process and to stabilize the dispersion during storage

They are built of linear or branched polyacrylate or polyurethane structures with a molecular weight between 5,000 g/mol - 30,000 g/mol and have special groups which have high affinity towards specific sites on the pigment surface. These are called anchoring groups, and are built in at strategic points on the polymer backbone.

Low molecular weight wetting and dispersing agents

They are categorized according to their chemical structure and the nature of their hydrophilic groups (amphoteric, cationic, … etc). The molecular weight is between 800 and approximately 2000 g/mol which is too low to give enough steric hindrance for stabilization of organic and carbon black pigments.

The interaction of their polar groups with the pigment surface and the behaviour of the nonpolar chains in the medium determine their effectiveness.

Mode of action

The polar heads will form hydrogen bonding interactions between different pigment units resulting in a network that enhances the separation of the particles (controlled flocculation). Inorganic pigments are usually metal oxides which contain positive metal ions and negative oxide ions. These ions are good anchoring points on which the anchoring groups of the dispersion control additive can attach to (polar interactions).

Pigment stabilization by hybrid dispersants

Hybrid dispersant are modern low molecular weight dispersants. They contain anchoring mechanisms similar as in high molecular weight dispersants but have significant lower molecular weights varying between 1000 – 5000 g/mol. Due to the anchoring groups, multi adsorption is possible and therefore anchoring on organic- & carbon black pigments can be achieved. Compared to conventional low molecular weight dispersants the molecular weight of these hybrid dispersants are usually much higher which ensures more improved steric hindrance.

The active substance of hybrid dispersant is typically 100%. Because high molecular weight dispersants are usually having 30 – 60% activity, hybrid dispersants are very cost effective to use.

Unlike conventional low molecular weight dispersants, hybrid dispersants can be used for inorganic-, organic- and carbon black pigments.

Example of a hybrid dispersant polymer with ‘triple tail’ technology.