Modern toners contain magnetite with tailored physical and chemical properties. The high-performance Bayoxide® E 8700 grades have a particularly narrow particle size distribution, defined particle shape and made-to-measure magnetic properties.

Most laser printers work with low coercive toners (ca.60 Oe) which have a low remanent magnetization. Only spherical oxides fulfill this requirement. Special reactors and the use of sophisticated recipes are necessary to produce these oxides. Many copier formulations contain cubic and octahedral magnetites. Versions with a small particle size are also used in some of the newer laser printers and multifunctional machines.

The consumer requires toners with a high image density (blackness) at a reasonable yield. While the balance between yield and image density can be influenced by changing the magnetite content of the toner, both yield and image density can be optimized at the same time if oxides with high tinting strength are used. In recognition thereof, most of the LANXESS grades have an outstanding tinting strength and a bluish black color which is preferred by most consumers.

Because of their low fusing temperature, the use of polyester-based formulations allows the construction of fast printers. However, the dispersion of the pigment requires more energy and time than the dispersion of styrene co-polymers, resulting in a reduced capacity and higher production cost. Untreated magnetites also adsorb a mono layer of water molecules if the unpacked product is in contact with humid air, as is often found in Asian countries. This can be a problem in water sensitive polyester formulations. It can be solved if surface-treated oxides such as the “H-grades” from LANXESS are used. The hydrophobic and lipophilic nature of these products has a positive impact on wetting and dispersibility and allows the production of toners with improved fogging characteristics and low humidity sensitivity.

The Global Competence Center Specialties will gladly answer individual customer inquiries with respect to this field of application or provide further information about LANXESS pigments.