Cerium sulfide pigment

Cerium sulfide pigments are produced from hydrated cerium oxide or oxalate and calcined in an oxygen-free, sulfide environment. They are silica-encapsulated to minimize water-reactivity and to improve heat stability and chemical resistance properties. Because of their low relative value-in-use, they are used primarily in engineering plastics and in particular the polyamides where high-performance organic colorant alternatives and other inorganic pigment alternatives are few. 

Cerium sulfide pigments are prepared in three steps (Figure 4—7) ... 

Cerium Sulfide Pigment Manufacture 33 Figure4—8 Coated cerium sulfide. 

Figure 4-9 Absorption (K) and refraction (n) indices of cerium sulfide pigment.

Table 4-3 indicates, for the range of existing cerium sulfide pigments, the typical quantity of pigment necessary to achieve a standard depth of shade of 1/25, when combined with i % rutile TiO pigment. 

Table 4-3 Ti nting strength of cerium sulfide pigments in plastics.

Cerium sulfide pigment Light orange Orange Red Burgundy... 

Cerium sulfide pigments provide relatively high opacity and hiding power, similar to cadmium and lead-based pigments. 

Cerium sulfide pigments can be used either alone or in combination with other pigments and colorants to obtain orange and red shades. They are also successfully employed as shading pigments in pastels and beige tints. 

Cerium sulfide pigments can be readily dispersed in a variety of polymeric resin systems using conventional plastics processing equipment. They are both non-dusting as well as dispersible (Figure 4—10). 

Besides the fact that they are compatible with most thermoplastics, cerium sulfide pigments can also be used in a wide range of other polymers including engineering plastics, thanks to their very good heat stability. 

Thanks to their strong UV absorption characteristics, cerium sulfide pigments are not only light-fast (Table 4—5), but can protect the medium in which they are incorporated from deterioration by UV light (Figure 4—11). 

Hence, cerium sulfide pigments can be used advantageously in very demanding, high light-fastness applications such as automotive interiors. 

Paint grade cerium sulfide pigments exhibit very good durability in both the xenon test and outdoor exposure. In QUV-A testing, however, the humidity conditions of the experiment are too severe to be representative of outdoor exposure. 

Cerium sulfide pigments are also good candidates for automotive paints, due to the IR reflectance properties of Cerium compounds (Figure 4—15). 

Cerium sulfide pigments are also used for some applications in printing inks and... 

Cerium sulfide pigments (NEOLOR ) are almost completely insoluble in water, and the cerium ion shows effectively no toxicity (acute or chronic). As predicted, cerium sulfide pigments have shown no risk to humans or the environment. Acute oral toxicity LD50 rat, oral >5000 mg/kg l Tests for irritation to the skin, eyes, or mucous membranes have also shown no adverse effects, as have tests for potential skin sensitivity l... 

Cerium sulfide pigments also show no genotoxic or carcinogenicity effects. Bacterial and in vitro gene mutation assays (OECD 471 476) fail to show mutagenic activity. In vitro chromosomal aberration tests (OECD 473) show no clastogenic activity. Additionally, sub-chronic toxicity (28 day, OECD 407) studies show no significant adverse effects (dose of 150 mg/kg/day), unlike cadmium and some other pig-ments . ... 

Cerium sulfide pigments show no harmful effects on the environment. The pigments are virtually completely insoluble. They show no mobility and readily form deposits in the soil. Further studies show they are not harmful to the aquatic environment EC 50 Daphnia magna, 48 h) >100 mg/L)l. ... 

In the production process, inadvertent reaction with moisture, acids, and heat may result in the release of small amounts of hydrogen sulfide. Therefore, an exhaust air system is recommended for handling cerium sulfide pigments. The exhaust air might also require scrubbing for hydrogen sulfide removal, and state, local and national regulations should be carefully consulted. 

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