Pigment preparation
Pigment preparation , colloquially pigment paste , describes a commercial form of pigments . It is a liquid mixture in which the pigment is already dispersed . You will e.g. B. used for coloring paints , emulsion paints and printing inks . Pigment preparations in a liquid binder are called liquid colors .
composition
In principle, pigment preparations contain the same starting materials as their target system, e.g. B. a paint. However, pigment preparations do not aim at the final properties of a lacquer, but rather serve the sole purpose of pigmentation.
Input materials are:
- pigment
- Water or solvent , depending on the target system
- Wetting and dispersing agents
- Binder (optional)
- Retention aid (optional)
Since the aim of pigment preparation is to simplify incorporation, the pigments must be dispersed . Wetting and dispersing additives are required for dispersion (wetting by the surrounding medium, dividing the pigment and stabilization). The choice of wetting and dispersing agents depends on the pigment itself, but also on the target system to be pigmented. If this contains additives that can interact with the additives of the pigment preparation, the stabilization can break down. The result is flocculation in the colored (finished) product. This is known as intolerance.
The other ingredients are determined by the type of application. Solvent-based pigment preparations are used for solvent-based paints, aqueous pigment preparations for water-based paints and emulsion paints. There are also so-called aqueous universal pastes that can be used in both aqueous and solvent-based systems. However, since water is always dragged into solvent-based paints in this way, drying and mechanical properties can be significantly negatively affected. Usually these systems can only be used in paints and emulsion paints and are therefore not really universal.
Retention agents must be used especially in tinting systems on an aqueous basis . These are substances that prevent the water contained in the formulation from evaporating . But since this z. B. are still contained in a freshly painted, just drying emulsion paint, overdosing can lead to poorer drying properties.
Advantages and disadvantages compared to powdered pigments
The greatest advantage is that the pigment is already dispersed, which means that the most costly production step is no longer necessary. In addition, pigment preparations can now be set very precisely with regard to color strength and coloristic behavior . Well-tolerated pigment preparations can be used in various, ideally in all, paint systems of a paint manufacturer. Not every pigment has to be dispersed in every system, which significantly reduces the complexity of production.
It is disadvantageous that the dispersing step takes place at the preparation manufacturer's and thus leads to a restriction in the choice of pigments and, on the other hand, to an increase in the price of the product. The latter, however, is usually compensated because the pigment preparation manufacturer can produce larger quantities, which is more economical. An interim solution is often used in which the large-volume pigments are purchased as a powder and the preparations are made by the paint manufacturer himself, but the small-volume tinting pigments are purchased as a preparation.
Tinting systems
A tinting system is the combination of several (mostly 12 to 20) pigment preparations, which are connected to one another via a dosing system and a software solution for color management. The complex formulation maintenance is also part of the tinting system .
Types of tinting systems are so-called point-of-sale tinting systems or in-plant tinting systems . Point-of-sale systems are tinting machines that are set up directly at the point of sale, e.g. B. in a hardware store. These essentially produce small quantities. In-plant tinting refers to the production of large quantities of a color in the paint manufacturer's production. The production of larger quantities is more economical here.
When choosing a pigment for a tinting system, it must be ensured that as few pigments as possible are used to cover as many shades as possible. This means that tinting systems for industrial or automotive refinish paints have to contain more pigments, since ruby and metallic tones (transparent pigmentation) usually also have to be covered. For emulsion paints , these areas usually do not have to be covered. However, pigmentation variants for cheap interior wall paints and high-quality facade paints are usually provided here.
Current developments
In connection with the Decopaint guideline , pigment preparations were developed which, like the paint systems themselves, no longer contain any VOCs . VOC-containing pigment preparations would not themselves be affected by the regulation. However, they would increase the VOC content in the finished paint and are therefore still undesirable.
Solid preparations for aqueous applications can now also be found on the market. Like liquid pigment preparations, these are easy to stir in and are also made from them using a special drying process. Despite good processability, this increases the costs so much that these products have not yet become widely accepted. With point-of-sale tinting systems, in particular, there are also difficulties in precisely metering the tinting pigments to be added in small quantities.