White pigments

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Titanium white pigment, ( white pigment )

White pigments are achromatic inorganic pigments with a high refractive index (greater than 1.8), which are usually produced synthetically and are primarily used to produce optical whiteness in paints or as fillers in e.g. B. plastics are used. Titanium dioxide is the most important white pigment with the highest refractive index . In comparison, some other white pigments:

White pigment Refractive index n D
Titanium dioxide (anatase, rutile) 2.6-2.7
Lithopone 1.8-2.1
Barium sulfate 1.64
Zinc oxide (zinc white) 2.0-2.1
Zinc sulfide 2.4
Lead carbonate (white lead) 1.8

In connection with the application as a paint, the refractive index is primarily a measure of the wet opacity or the hiding power . With regard to dry opacity (for example for paper coating) and for assessing the degree of whiteness , it is less meaningful. Thus, white minerals such as with a lower refractive index. B. chalk (n = 1.55) or satin white can achieve an opacity comparable to that of white pigments, because the particle size and shape are also decisive. Normally, the finer the particles, the better the hiding power. Depending on the manufacturing conditions and the fineness of the grinding, particle sizes below 0.1 µm can now be produced.

The main areas of application for white pigments are in the paper, paint, plastics and coatings industries.

In the paper industry, the white minerals such. B. calcium carbonate and ettringite (satin white / casul) counted among the white pigments. They are used here for coating (coated) papers, which are used as art paper and for high-quality food packaging. White minerals are also used in emulsion paints and liquid plasters.

literature

  • Wolfgang Tegethoff (Ed.): Calcium carbonate. From the Cretaceous into the 21st century. Birkhäuser, Berlin a. a. 2000, ISBN 3-7643-6424-6 .
  • Entry to white pigments. In: Römpp Online . Georg Thieme Verlag, accessed on January 2, 2015.
  • Olaf Lückert: pigment and filler. 5th edition. Laatzen 1994, ISBN 3-927342-04-1 .
  • DIN 55943 colorants
  • DIN 55945 coating materials
  • Thomas Brock et al. a .: Textbook of paint technology. Hanover 1998, ISBN 3-87870-547-6 .