Clays calcined

Organofunctional silanes are used to promote polymer-to-filler bonding with clay or siHca fillers. Vinyl silanes are used in peroxide-cured wire insulation to promote stronger bonding with calcined clay fillers. Mercapto silanes are used to treat kaolin clay in sulfur-cured compounds. 

Fig. 2. (a) Brightness improvement obtained by the use of kaolin as a filler in paper and (b), opacity improvement obtained as pulp fibers are replaced with various kaolins. In both cases, A represents fine-particle calcined clay B, high brightness No. 1 kaolin C, coarse-particle water-washed kaolin and D,... 

Mineral fillers are used for light-colored compounds. Talc has a small particle size and is a semireinforcing filler. It reduces air permeabihty and has htde effect on cure systems. Calcined clay is used for halobutyl stoppers in pharmaceutical appHcations. Nonreinforcing fillers, such as calcium carbonate and titanium dioxide, have large particle sizes and are added to reduce cost and viscosity. Hydrated siUcas give dry, stiff compounds, and their acidity reduces cure rate hence, their content should be minimized. 

Carbon blacks are usually used as fillers. The semi-reinforcing types, such as PEP (Past Extmsion Pumace) and SRE (Semi-Reinforcing Pumace) give the best performance (see Carbon, carbonblack). To lower the cost and improve the processibiUty of light compounds, or to lower the cost of black compounds, calcined clay or fine-particle calcium carbonate are used. 

Fireclays can be dividea into plastic clays and hard flint clays they may also be classified as to alumina content. Firebricks are usually made of a blended mixture of flint clays and plastic clays which is formed, after mixing with water, to the requirea shape. Some or all of the flint clay may be replaced by highly burned or calcined clay, called... 

Calcined clays are hard clays which have been heat treated to remove the combined water. The removal of any surface bound entity from the clay particles improves the capacity to improve the electrical resistance of rubber compounds. Calcinated clays also reduce compound water... 

Aloton Also called Buchner. A process proposed for extracting aluminum from clay. Calcined clay is leached with ammonium hydrogen sulfate solution under pressure, and ammonium alum is crystallized from the liquor. Invented by M. Buchner in Hanover-Kleefeld in 1921 piloted in Germany in the 1920s and in Oregon in 1944. It was never commercialized, but provided the basis for the Nuvalon process which was. 

While organo-silane treatments are extensively used in both thermoset and elastomer applications, their use in thermoplastics has so far been somewhat restricted. This is because they do not react with the surface of calcium carbonate, one of the principal fillers used in this type of polymer and because of the lack of a suitable reactive functionality for most of the thermoplastic polymers. Today they are principally used in conjunction with glass fibres, calcined clays, aluminium and magnesium hydroxides, micas and wollastonite. The main thermo-... 

Clay minerals are widely used in the filler industry and the production of the various types has been described by Hancock and Rothon [85]. The products available range from unaltered kaolin to products produced by calcination. Kaolin deposits are widespread throughout the world. While simple clay minerals are extensively used as fillers in elastomers, their use in thermoplastics is more restricted and the principal products used are those obtained by calcination of ka-olinite. Thus metakaolinite finds application in PVC and silane treated calcined clay in polyamides. The production of these forms only is discussed below. 

The second material is simply known as calcined clay and is formed when kaolin is heated above 1000 °C. This is an amorphous material with a defect spinel structure. A few isolated hydroxyls are retained on the particle surface and this enables the material to react with materials such as organo-silanes. 

The principal use of calcined clay in thermoplastics is in polyamide moulding compounds, for which purpose it is normally coated with an amino functional organo-silane. 

Fillers. Fillers are used to improve strength and stiffness, to lower cost, and to control gloss. The most common filler is calcium carbonate, which ranges in size from 0.07 to well over 50 m. Some forms are treated with a stearic acid coating. Clay fillers, such as calcined clay, improve electrical properties. Glass fibers, talc, and mica improve tensile strength and stiffness, but at a loss in ductility. 

Calcinated clay Vinyl Burgess KE Burgess Pigment... 

Aloton Also called Buchner. A process proposed for extracting aluminum from clay. Calcined clay is leached with ammonium hydrogen sulfate solution under pressure, and ammonium alum is... 

Temperature programmed reduction of calcined clay samples revealed that their reducibility was sensitive both to the thermal pretreatment conditions as well as to Al/Al+Si ratio (Figure 3). Table III summarizes the degree of reduction to Co, as measured from the H2 uptake to 450 C. On samples previously calcined to 600 C, reduction to form metallic Co was confirmed by both XPS and SAD. 

Under certain conditions, there are definite advantages in using hydrochloric, nitric, or other acids to carry out a dissolution step. In their evaluation of proposed processes for the recovery of alumina, Peters ei al. (P8) cited earlier experimental work which showed that both hydrochloric and sulfuric acid are equally good in extracting alumina from calcined clay (TIO). In the separation of the leach liquor from the silica residue by filtration, the chloride solution rapidly separated, while the sulfate solution did not separate easily. In addition to ease of filtration, the hydrochloric acid leach also made the later removal of iron easier. The insolubility of titanium dioxide in hydrochloric acid also eliminated another separation problem. Under this particular situation, hydrochloric acid was the natural choice. As in most large leaching operations, the acid would be recovered and recycled. 

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