By Koenig, Gerd
Only high performance pigments are used to colour automotive and industrial finishes and architectural paints. Users expect not only excellent colouristic properties but also pigments which are, depending on the application, lightfast, thermally stable and resistant to weathering and chemicals.
Pigments should also be safe to use and easy to handle and these requirements are increasing continuously. What developments are in sight? What are the trends?
Trend to water-based systems Generally, there is a reduction in the use of solvents in all application areas.
In OEM automotive finishes, for example, waterborne and high solids coatings are now dominant. In contrast to Europe where environmentally friendly water-based paints are preferred, solvent-based high solid (HS) coatings predominate in the USA and Japan.
Even there, however, the trend is to water-based systems(fig. 2). The quinoxalindione-derivative Hostaperm Yellow HSG (Pigment Yellow 213) developed specially for water-based coatings reflects this trend. First class fastness properties are combined with excellent compatibility and application performance in water-based coatings.
Many problems with organic yellow pigments in high performance multi-layer coatings, e.g. weather fastness, paint shelf life, low colour strength, bleeding into the clear coat, etc, have now been solved.
Stylists and formulators throughout the world appreciate its colouristic potential which allows the use in both metallic and solid shades.
The coexistence of water-based and HS coatings requires the formulator to develop shades which match in both systems with very close tolerances.
New developments in this sector include so-called twin-pigments: Based on an identical basic pigment they have been subjected to different surface modification. An example is the twin- pigment Hostaperm Red Violet ERX and ERX-WD (Pigment Violet 19).
These pigment twins are distinguished by the fact that the colouristic properties of ERX in solvent-based coatings correspond to those of ERXWD in water-based systems. Specialised multi-purpose pigments. as described above, are not a paradox contradiction. Clariant has made a formulator's dreams come true.
Powder coatings
In the light of the aim to reduce solvent levels, powder coatings are also a growing market. Although numerous pigments from the liquid coatings sector are suitable for use in powder coatings, exceptional heat resistance is nevertheless a prerequisite, The pigments must withstand processing temperatures of over 200[degrees]C.
Innovations include the new Colour Index Novoperm THI Red 4G 70 VP 2543. This yellowish red pigment exhibits a brilliant pure colour and is suitable for use in powder coatings as a result of its good hiding power and high heat resistance.
Also new on the market are the "PCA" pigments specially developed by Clariant for Powder Coating Application: Novoperm Red F3RK 70PCA shows considerably less tendency to bake on and stick in the premixer than other commercial P. Red 170 types.
The second pigment, Hostaperm Red Violet ER-PCA, is a pure beta modification of quinacridone. The finish process for this product is optimised to facilitate incorporation in powder coatings and to achieve high colour strength.
VOC-free pigment pastes
The architectural paints industry traditionally uses pigment preparations for colouring emulsion paints, but tinting systems are increasingly important.
Increasing environmental awareness is reflected in this sector by the demand for VOC-free pigment pastes. This demand conflicts with the need for resistance to drying out and long term dispensability of water-based pigment pastes since these properties are usually determined by the content of solvents such as propylene glycol.
The new Colanyl 500 range is a response to this market demand. The water-based, binder-free pigment preparations are VOC-free and are characterised by excellent technical properties. Specialist dispersing agents in combination with high molecular polyglycols ensure the necessary resistance to drying out for this range of products. Other key properties, such as shelf life, processability and colouristic tolerances, are equivalent to traditional preparations like the "Colanyl 100" range.
Narrower tolerances
Some paint manufacturers prefer to make their pigment pastes in-house. To minimise adjustment work in the production of such pastes, closer pigment tolerances would certainly help.
Clariant's "TS range" consists of selected, high quality pigment powders for precise, reproducible manufacture of pigment pastes. The range is distinguished by very narrow quality tolerances (colour strength [+ or -] 4 %, _H [+ or -] 0,4, _C [+ or -] 0,6, _E [less than or equal to] 0,7).
The development of the new Hansa Brilliant Yellow 2GX 70-S (P. Y. 74) aimed at the same target but took a different approach: Quality variations of pastes containing opaque P.Y 74 stem from its tendency to recrystallisation: The crystallite size distribution changes during extended storage leading to poor constancy of colour and colour strength.
The new pigment has been stabilised to this effect, and as a consequence, the production of pastes with Hansa Brilliant Yellow 2GX 704 is much more stable and predictable in its results, while at the same time, these pastes have a better long-term constancy of colouristic properties.
Future challenges
The dispersion step in the manufacture of pigmented coatings is complex and therefore expensive. Developments are thus aimed at ever easier to disperse pigments.
Pigment manufacturers are meeting this long-term challenge using various approaches whereby conventional pigment preparations will continue to play an important role.
To meet this challenge, Clariant's Pigments & Additives Division is also working on the development of new, very easily dispersible powder pigments.
A characteristic for mature markets, such as Paints, is the pressure on prices throughout the manufacturing chain. The challenge is to supply pigments with constant, superior quality, produce them at lower cost and furnish them with special properties that help paint manufacturers to reduce their production cost too!
One of Clariant's approaches to meet market expectations is the use of innovative technologies such as the micro reaction technique, which are opening up totally new perspectives. Research on a miniature scale is able to meet customer demand for innovation at shorter and shorter intervals. In this technique, several dozen capillary ducts form the chamber into which the reactants are fed, mixed and then react with each other. The desired product is formed within seconds. A three stage pilot plant at Clariant with several parallel microreactors has recently started production of a yellow azo pigment by a continuous process (fig. 3)
Conclusion
Close co-operation with processors is a key component in this success. Other essential factors include experience, know-how, quality management and a global network. Colour is fashion and as such is subjected to fashion trends within the society.
Figure 2. Waterbourne base coats for the automotive industry--market
share and growth trends.
Germany 90%
Europe 45%
USA 30%
Japan/Asia <10%
Dr Gerd Konig
Manager of Market Segment--Automotive & Industrial Coatings, Clariant
Email: koenig@olariant.com
Web: www.clariant.com
