Pigmentary

A process has been developed by J. M. Huber Co. to treat kaolin clay pigments using a hydrothermal process (see Clays) (25). The products, called synthetic alkah metal aluminosihcates (SAMS), have superior pigmentary quahties for paper (qv) coating. 

Whereas the worldwide production of 2inc oxide [1314-13-2] is estimated to be around 500,000 t aimuaHy, only about 75,000—100,000 t are used for pigmentary appHcations by the paint industry. About 250,000 t are consumed by the mbber industry, and the rest is used in the production of plastics, paper, cosmetics, pharmaceutical products, ceramics, and glass (see Zinc compounds). 

The concentrated mother Hquor contains a large amount of sulfuric acid in a free form, as titanium oxy-sulfate, and as some metal impurity sulfates. To yield the purest form of hydrated TiOg, the hydrolysis is carried out by a dding crystallizing seeds to the filtrate and heating the mixture close to its boiling temperature, - 109° C. The crystal stmcture of the seeds (anatase or mtile) and their physical properties affect the pigmentary characteristics of the final product. 

Whereas the hydrolysate, TiOg does not have any pigmentary properties, its physical characteristics such as particle size eventually affect its value as... 

To produce the titanium white mtile pigment, the hydrated Ti02 gel prepared in the presence of mtile seeds is calcined at temperatures of 900—930°C. This temperature is quite important because pigments having a particle size of 200—400 nm are produced at these temperatures. When the calcination is carried out at temperatures above 950°C, the particles of Ti02 become considerably larger and do not have optimum pigmentary properties. 

Llthopone. Lithopone is a mixture of ZnS and BaSO. The pigmentary properties of the mixture are deterrnined by 2inc sulfide and therefore Hthopone pigments are characteri2ed by the amount of ZnS present in the mixture. The amount of ZnS in commercial Hthopones varies from 15 to 60%. The most common is a 30% Hthopone pigment, containing 28—30% of ZnS and 70—72% of BaSO. ... 

In the calciaation process, a mixture of corresponding oxides and an optional modifier, eg, molybdic acid, are milled together to achieve a homogenous mixture. The mixture is calciaed at 750—950°C and milled to a desired particle size. Wet milling ia an alkaline medium is recommended to remove any unreacted vanadium salts that ate beheved to degrade the pigmentary properties of bismuth vanadate (39). 

The coarse, nonpigmentary cmdes are particle si2e reduced by a variety of processes to obtain pigmentary CPC. Since CPCs are utili2ed in a variety of industries and a host of appHcations, the specific property requirements vary widely. A large number of special-purpose types are commercially available designed to provide optimal properties for specific appHcations. 

Due to the excellent pigmentary properties, quinacridones are used in many industries but particularly in automotive finishes, emulsion paints, plastics, and fibers. 

Precipitation of a hydrated titanium oxide by mixing aqueous solutions of titanium chloride with alkaU forms the precipitation seeds, which are used to initiate precipitation in the Mecklenburg (50) variant of the sulfate process for the production of pigmentary titanium dioxide. Hydrolysis of aqueous solutions of titanium chloride is also used for the preparation of high purity (>99.999%) titanium dioxide for electroceramic appHcations (see Ceramics). In addition, hydrated titanium dioxide is used as a pure starting material for the manufacture of other titanium compounds. 

Pigmentary dyschromias including melasma and post-inflammatory hyperpigmentation... 

Clinically, photodamaged skin is characterized by coarse and fine wrinkling, mottled pigmentary changes, sallowness, textural rough-... 

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