Mixed phase oxide pigment
Mixed phase oxide pigments are a group of extremely stable, inorganic pigments . Mixed-phase pigments are not, as the name might suggest, mixtures of pigments, but rather solid solutions of metals in metal oxide compounds .
Classification and structure
Mixed-phase oxide pigments are divided into groups according to their chemical structure. Here, have spinel and rutile , the most important as the basis crystals.
Titanate pigments
The most important subgroup of mixed phase oxide pigments are titanates , which are derived from titanium dioxide . The crystal structure is the rutile structure with substitutions on the titanium site. The two most important representatives are nickel antimony titanate , CI Pigment Yellow 53 (colloquially: nickel titanium yellow) and chromium antimony titanate, CI Pigment Brown 24 (colloquially chrome titanium yellow). While nickel antimony titanate is a greenish yellow pigment, chrome antimony titanate has a reddish hue. Nickel antimony titanate is mainly used when the more opaque and stronger color bismuth vanadate is not stable enough. B. is the case in a strongly basic environment. Chromium antimony titanate, on the other hand, has a color that is difficult to achieve with other high-quality pigments, so it is used relatively frequently.
Nickel antimony titanate
C.I. Pigment yellow 53
Chromium antimony titanate
C.I. Pigment brown 24
Chrome antimony titanate, yellowish
C.I. Pigment brown 24
Spinel pigments
Cobalt aluminate (CoAl 2 O 4 ), commonly known as cobalt blue , is listed in the Color Index under CI Pigment Blue 28 (red-tinged) and CI Pigment Blue 36 (green-tinged, aluminum is partially replaced by chromium ). These are relatively pure pigments that are always used where the level of fastness of copper phthalocyanine is insufficient. There are also several pigments that are known under the name spinel black , but are listed in the Color Index under different names depending on the secondary component. Examples include CI Pigment Black 28 (chrome, copper ), CI Pigment Black 30 ( nickel , chrome) and CI Pigment Black 33 ( manganese ). All are based on iron oxide black (Fe 3 O 4 ), whereby iron (Fe) is partially replaced by the elements mentioned. They are used when carbon black is a problem.
The only significant representative with an inverse spinel structure is cobalt titanate (Co 2 TiO 4 ), listed in the Color Index under CI Pigment Green 50. It is known colloquially as "cobalt green" and is a pure green pigment. This is used when phthalocyanine green does not meet the requirements, but chromium oxide green produces a color that is too cloudy.
Cobalt chrome spinel, bluish
C.I. Pigment blue 36
Cobalt chrome spinel, greenish
C.I. Pigment blue 36
Cobalt aluminate
C.I. Pigment blue 28
Copper
Chromite Black C.I. Pigment black 28
Iron Chrome Spinel
C.I. Pigment brown 35
properties
Characteristic for this group of pigments is the similar property profile. Most of the pigments have an excellent level of fastness, both in terms of weather resistance as well as temperature and chemical resistance. At the same time, the pigments show only a low color strength . Since these are mostly very fine particles with low porosity , this disadvantage can be partially offset by a higher pigmentation. Mixed-phase oxide pigments have a pure hue compared to other inorganic pigments such as iron oxide pigments or chromium oxide green . The often high price is a disadvantage. Some mixed-phase oxide pigments, such as CI Pigment Brown 35 (chrome, iron) or spinel black, show a higher reflectance in the NIR than carbon black. This causes the color to heat up less in sunlight.
use
This group of pigments is used almost exclusively in areas of application where the use of organic pigments is not possible and the setting of the desired color shade is not possible with the exclusive use of other inorganic pigments. Applications therefore include high-quality facade paints , varnishes for exterior use and enamel . Since the primarily used pigments mentioned above all also belong to the weather-resistant pigments, the range of application of mixed-phase oxide pigments is limited. A relatively new application are pigments for paint systems ( low absorption ), which have a maximum degree of reflection in the infrared and are thus intended to reduce the cooling requirements of buildings.
Individual evidence
- ↑ a b c d e G. Buxbaum, G. Pfaff: Industrial Inorganic Pigments. 3. Edition. Wiley-VCH, Weinheim 2005, ISBN 3527303634 .
- ↑ a b c The Society of Dyers and Chemists; Color Index. Third edition; Second Revision, Charlesworth & Co., Huddersfield 1982.
- ↑ " http://www.farbundlack.de/content/download/68163/843439/version/1/file/154801.pdf " Paints and varnishes, "Black and still cold"
- ↑ Brief information about Arctic pigments from Shepherd Color ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
