Titanium pigments replacement

Although white lead was the oldest white hiding pigment ia paints, it has been totally replaced by titanium dioxide, which has better covering power and is nontoxic (see Pigments). Nevertheless, basic lead carbonate has many other uses, including as a catalyst for the preparation of polyesters from... 

Production. Zinc sulfide production started in the United States and in Europe in the 1920s. Starting in the early 1950s, 2inc sulfide, like most white pigments, was slowly replaced by the more superior titanium white. Zinc sulfide can be prepared by a process similar to the one used to manufacture Hthopone. In the first step, barium sulfide reacts with sodium sulfate to produce sodium sulfide solution ... 

Many inert pigments (often known as fillers) are incorporated into paper in addition to the cellulosic fibres. They may be added to improve certain optical properties—in particular opacity and brightness—or simply as a cheap replacement for costly fibre. The two most common pigments are kaolin (china clay) and chalk (limestone), but talc and speciality pigments such as titanium dioxide are also used. The particle size for general purpose fillers is normally expressed as an equivalent spherical diameter (esd) and this is determined from sedimentation data. Values for the common paper-... 

The most important industrial use of titanium is in the form of the dioxide (rutile or anatase) as a white pigment in the paint industry. Its outstanding property is its capacity or covering power this, with its relative chemical inertness, has resulted in its almost complete replacement of all other white pigments. Related uses arise in the paper, plastics, rubber, textile and vitreous enamel industries. 

Zinc Iron Brown. Variation of the zinc to iron ratio in red-brown iron spinel (ZnFe204), or replacement of some of the iron ions by aluminum and titanium ions, gives light to medium brown pigments. Inclusion of a small proportion of lithium ions considerably improves stability towards reducing agents, e.g., when the pigments are used to color plastics [3.87]. The partial replacement of iron ions by chromium(III) ions yields dark brown products [3.88]. 

For artists - and house painters - nothing came dose to matching the brilliance and depth of lead white and while there were alternatives, made from chalk, calcined bones, oyster shells, or even groundup pearls, they did not compare to lead white. Today this pigment is rarely used and that which is available is restricted to conservators and restorers. We are now aware how toxic this metal is - see page 204 -and lead white has been replaced by titanium dioxide, which delivers the same brilliant whiteness with no risk to health. 

In the 5 years that followed (1965-70), three additional producers—American Potash, National Lead, and Pittsburgh Plate Glass—opened chloride-process plants. Sales of composite titanium calcium-base pigments continued to drop, as they had done over the previous 5 years in which Du Pont had ceased to produce them. This was due primarily to their adverse effect upon the stability of latex systems and the rapid replacement of alkyd and oleoresinous flat wall paints by flat latex paints. Two so-called "maximum-durability" pigments were introduced during this period—one by Du Pont and the other by National Lead. These pigments, although produced by different methods, both essentially eliminated the photochemical reactivity of the base titanium dioxide. 

Highly structured, agglomerated amorphous silicates are a class of synthetically prepared pigments that are used in a variety of paper grades, where brightness, opacity, bulk, coefficient of friction and ink receptivity are considered critical properties. In many cases, precipitated silicas serve as partial or complete replacements for titanium dioxide. 

Figure 3.20 shows that PVC pigmented with high doses of titanium dioxide is still transparent to UV radiation up to 60 jxm from the material surface. This means that the surface of the pigmented article is never protected and has to be protected by the surface replacement mechanism explained in detail elsewhere or other means available (e g., surface coating orUV stabilizers). ... 

Because of price restrictions, there are attempts to replace titanium dioxide with less expensive pigment. Figure 3.24 shows results of such an attempt in which magnesium oxide was used as a replacement pigment. It is clear that the attempt was not successful because material elongation was drastically decreased even by small additions of magnesium oxide. 

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