Colour and effect pigments from Costenoble
Our colour perception arises from the scattering and reflection of certain parts of the incident light on a surface. This perception can be changed by the use of various pigments. The different character and coating of the pigments produces interference. Not only any number of colours but also specific effects such as rainbow and viewing angle-dependent colouring (so-called colour flops) can be produced. With this wide range of possibilities, we support the progress of innovative industrial sectors such as the cosmetics, plastics and paint industries. In doing so, it is important for us to constantly extend the design freedom of designers, technicians and decision makers by new trends and innovative product characteristics.
Pigments are organic or inorganic, insoluble colourants that are bonded to a carrier medium. They consist of irregular, granular, or also platelet-shaped substrates in the case of pearlescent pigments or glitter, that are coated extremely thinly and evenly in a special manufacturing process. The characteristics of the solid body and its chemical structure thus determine the characteristics of the pigment. The particle size of the pigment also provides the metallic appearance and can produce a brilliant velvety to glittering colour picture.
Pearlescent pigments do not contain any conventional light-absorbing pigments. Instead, the colours are produced by the effect of the interference of the light that is reflected from the differently coated surface of the pigments. In the case of thin coating, a white mother of pearl reflection colour is produced. Golden, red, blue to green reflection colours are produced with increase of the layer thickness.
Another visual characteristic of the pearlescent pigments is its capability to show a multicolour effect depending on the viewing angle. This appearance is called “goniochromaticity”. It arises when a small amount of a conventional light-absorbing pigment is mixed with an interference pigment. This goniochromaticity also includes the so-called “colour flop” or “flip-flop effect”. These show different colours at different viewing angles. Due to the greater goniochromaticity in comparison with aluminium pigments, pearlescent pigments are able to produce a greater flip-flop.
OSIXO® Pearlescent pigments for industrial applications
Costenoble distributes two basic types of pearlescence: OSIXO® PearlGloss and OSIXO® BismutPearl. They have a platelet-like form and have a relatively high refraction index. They have a gloss spectrum from smooth satin to brilliant glitter. Some OSIXO® pigments can also show colours using optical effects of light interference. Other OSIXO® pearlescent pigments – that are based on iron oxide coated glimmer – produce a metal effect without themselves being metal pigments. These special pigments are non-conductive, colour-fast, non-toxic and have high coverage. But mainly, they do not cause the usual application problems of metal pigments such as unwanted reactions or oxidation.
In addition to the glimmer-based pearlescent pigments, a wide range of pigments based on synthetic glimmers (OSIXO® SynPearl types) is also available. These are significantly whiter, more brilliant and more colourful than previous pearlescent types. The range is rounded off by the products with similar colours in the OSIXO® PearlGlass series that use “coarser” glass as a substrate and therefore glitter even more.
The OSIXO® pearlescent pigments optimised for outdoor applications have a patented weathering-resistant surface treatment.
OSIXO® pearlescent pigments are used in plastics as well as printing inks and paints for extrusion or injection moulding, in coatings, packaging or in the paper and textile sector for design of the surface. OSIXO® pigments are also used in the cosmetics industry.
OSIXO® pearlescent pigments are environmentally friendly, physiologically safe and non-toxic. They meet all requirements for a sustainable pigment. They open up possibilities for the user to implement new ideas in the colouring of materials and of the surface design.
The optimal concentration of the OSIXO® pearlescent pigments is 3-6%. Higher concentrations only increase the coverage marginally as a large part of the effect is lost due to light scattering. A pigment concentration of 1-1.5% over a coloured base is the most effective. A lower concentration allows the base paint to shine through better. The application concentration of OSIXO®-BismutPearl pigments is 2-4% bismuth oxychloride. Although all OSIXO®-BismutPearl products are provided with ultraviolet protection, further ultraviolet absorbers can always be added as bismuth oxychloride pigments tend to darken during exposure to ultraviolet light.
Gloss and effect losses can be produced for the combination of pearlescent pigments with other covering pigments and fillers such as titanium dioxide, chalk, kaolin or other metal oxides. In contrast, outstanding optical effects can be achieved with transparent dyes such as phthalocyanine blue or quinacridone red. For example, in practical use, a coloured base paint (white, black, coloured) is painted over with a low concentration top coat containing pearlescent pigments. If a higher coverage is desired, a covering pigment such as titanium dioxide or aluminium (in not too high concentration) can be used. Additional coverage can be achieved by using pearlescent pigments containing iron oxide or carbon black.
Paints with OSIXO® pearlescent pigments can be applied according to all usual techniques such as spraying, immersion, rolling or air brushes. In order to achieve uniform coverage, paints containing pearlescent pigments should be applied in multiple thin layers with approx. 1 to 2 minutes surface drying time.
When spraying lacquers, there must be a reliable air pressure of 2.5 to 2.8 kg/cm2; 3.2 to 3.5 kg/cm2 for most other paints and 3.5 to 4.2 kg/cm2. for synthetic resin paints. Thorough cleaning and degreasing are required for good adhesion. Spraying should be performed multiple times in a criss-cross motion (at least three times for a good film formation). The surface should dry in air between each spraying operation. Very good and uniform painting is usually achieved after the third coat. If a transparent lacquer top coat is to be applied, a longer surface drying time of at least 10 to 15 minutes is required.
Glass or plastic pearls are best coated using immersion. The temperature should be around 25 °C and the relative air humidity should be 50% or less. The immersion process and the dripping off afterwards should be performed at constant-intervals. Constant rotation of the material provides more uniform coating and reduces flow lines.
Special application areas
Due to their excellent temperature stability (up to 600 °C), OSIXO® pearlescent pigments are suitable for coating strip steel containing fluorocarbons. Acrylic, polyester and silicone resins can be used as binders. Depending on the appearance, the pigment concentration lies between 1 and 10% for “wet shiny” to “brilliant satin”. OSIXO® pearlescent pigments are also the pigment of choice for dry or powder coatings. Their thermal stability makes them ideally suitable for the burning-in system on epoxy, acrylic and polyester based resins.
OSIXO® pearlescent pigments can also be used without problem in water-based lacquers or paints. In contrast to metallic pigments that can oxidise or initiate chemical reactions, OSIXO® pearlescent pigments do not change due to their inert nature and do not initiate any reaction.