Paints and Coatings

Specialty Silica

As the world’s largest producer of performance silica, Evonik Degussa GmbH has in SIPERNAT® and ACEMATT® two excellent product ranges for the printing industry. A variety of specialized products can be tailored to virtually any specific requirement for the most varied printing inks, including water or solvent based inks, offset or rotogravure printing colors or even silkscreen printing. Depending on the field of application and specific end-user requirements, SIPERNAT® types can be used as extenders to improve flow or drying characteristics of printing colors, while ACEMATT® products will deliver excellent matting results.

Pigment Blacks

Its outstanding properties make pigment black the most commonly used black pigment in the paints, coating and lacquer industry. It is used in pure tone coloring (e.g. in automotive basecoats), as a darkening agent (e.g. in decoration) and for tinting transparency effects (e.g. for metallic effects and wood glazing).

The particular lacquer-specific behavior of pigment blacks results from the differences between the various manufacturing processes and the ensuing respective morphological and chemical properties. The positive effect in particular of oxidative post processing of pigment blacks plays a crucial role in almost any binding agent system.

Processing pigment black requires purpose-adapted formulations and processes that may vary significantly from those of other formulations.

Selection criteria for pigment blacks used in lacquers
The application parameters required for quality evaluation and assurance, such as dispersion behavior, pouring characteristics and weather stability as well as coloristics are to a large degree dictated by the following criteria:

• Medium primary particle size
• Surface chemistry
• Manufacturing process/Structure

Structure only plays a role in exceptional cases, e.g. when it comes to electrically conductive coatings. Here, pigment blacks with the highest possible structure will be most effective in achieving desired conductivity results.

Product-specific selection criteria

Medium primary particle size
The selection of pigment blacks is mostly done by coloristic criteria, with media primary particle size playing a significant role. The following rules apply to full-tone applications:

• The finer a pigment black’s particles, the deeper the color of the lacquer
• The better the stabilization of the pigment/binding agent mixture, the more bluish the lacquer will appear to be

This kind of pure tone would require 3-5% pigment black – based on binding agent – in order to produce a lacquer with good coverage properties.

Pigment black/titanium dioxide mixtures show different coloristic ratios:
Fine pigment blacks used with titanium dioxide will produce a more brownish gray (e.g. RAL 7038, 7045 etc.) and have a high coloring capacity. Coarse pigment blacks, on the other hand, show a rather bluish gray (RAL 7001, 7046)h and lower color strength.

Further trials with gray lacquers have shown that, besides the median primary particle size of the carbon black, the particle size of the titanium dioxide and its PVC (pigment volume concentration) also has a major effect on the end color result. Experience shows that fine titanium dioxide will yield bluer gray tones than the coarser-grained type. Raising the PVC index of titanium dioxide will increase the blue tint.

Please refer to technical Bulletin 37 “On the color of deep black and gray paints and lacquers” for additional information.

Pigment blacks, albeit in small concentrations, are also used in metallic paints as are common in the auto industry. The same rules apply to color specifics as with pigment black/titanium dioxide mixtures.

High brilliance and a brownish tint characterize fine-particulate pigment blacks. In addition to a bluish tint, pigment blacks with larger particles also produce a certain degree of opacity.

The particle size also affects other application – specific aspects, as for instance dispersion behavior, rheology and resistance to weather exposure.

Surface chemistry
Oxidative post-treatment enhances carbon blacks versus non-oxidized carbon blacks in a number of process and application – related areas to better serve end-product objectives. Specifically:

• Dispersion
• Rheology
• Color depth
• Tone
• Pouring characteristics
• Gloss and haze
• Weather resistance

are markedly improved.

System specific influencing factors
Besides the criteria that are specific to carbon black and which have an impact on pigment behavior in the paint or lacquer compound, special care must be given to the influence of paint/lacquer – specific parameters to ensure an optimum result.

Binding agents with a good pigment coverage factor should be used for the rubbing compound, with the optimum binding agent concentration being a matter of testing.
Good dissolvers are important for grinding compounds and their viscosity should be adapted to the system used.
With bead grinder dispersion, we recommend grinding compounds with a high specific weight and a low diameter (<2mm)

Matting Agents

INXEL Pigment Preparations