Air-floated clays

Clay can be generally divided into soft and hard clays on the basis of their producing softer and harder rubber compounds at a given loading level. There are several processes for producing clay for rubber reinforcement from the mined form (1) Air-floated clay, in which the ore is milled to break up lumps and air... 

Air-floated clays are less expensive than those produced from the water sedimentation process. However, those clay fillers obtained from water sedimentation, sometimes called water-washed clays, can be brighter in color, possess less iron impurities, have better particle size control, and have a lower level of impurities such as alpha quartz (which can be a hazard to workers if inhaled). 

Air floated elays are beneficiated by dry grinding and air classification. The quality of the raw material, specifically in the areas of brightness and the presenee of eolored impurities, is very important to an air floated clay. Dry processing ean only make minor improvements in brightness. Impurities such as quartz, titanium dioxide, mica or iron oxide carmot be removed by air flotation exeept as oversized particles. In general, air floated cl s are lower quality than water washed cl s and find only limited use in paper making. 

Cement. Portland cement, a mixture of calcium siUcate and calcium aluminate minerals, is produduced by the calcination of argillaceous limestone or mixtures of limestone and clay (see Cement). Although other clays can be used, ka olin is preferred because of its alumina and siUca content and low level of impurities. It is especially desirable in the manufacture of white cement and other types requiring careful control of chemical composition. Air-floated ka olin, because of its low cost, is usually used. 

Imerys leads the European market for polymer end use. The aforementioned four companies supply the majority of the world s water-washed kaolin and are major exporters of the mineral. Other key producers are Thiele with 1.25 mtpa and Quarzwerke owned by Amberger Kaolinwerke (AKW) with 0.9 mtpa. Other US producers of air-floated grades are KT Clay (owned by Imerys) with >500 000tpa and Unimin with >500 000 tpa. It should be noted that European kaolin comes mostly from primary deposits and does not lend itself to the air-flotation process [10]. 

Secondary clays are usually very much finer than primary clays and products that are approximately 100% finer than 5 pm can be obtained by a fairly simple air-float or degritting procedure. 

Clay is used in almost all filler applications because of its high cpiality and reasonable priee. Filler clays usually fall into the category of "soft clay", having a particle size of 60% minus 2 microns, and a GE brightness of 80 to 90 depending on grade. They may be air floated or water processed and are delivered to the papermill either as powders with dispersant added, or 70% solids aqueous slurries. This greatly facilitates preparation of the clay for the paper maehine. 

Kaolins are used primarily in wire and cable insulation where the calcined clay gives good electrical characteristics, a smooth surface and good resistance to humidity. Air-floated kaolin clay is used in polypropylene in automotive applieations to increase viscosity and thereby improve proeessability. 

Bucar 5214 - butyl rubber (Occidental Chemical Corp.) Snobrite - 0.8pm air-float kaolin (Evans Clay Co.)... 

There are many versions of clays (hydrated aluminum silicate) available including soft clay, hard clay, air floated, water washed, calcined, and surface-treated versions. Surface treatments include stearates, mercapto-silane, vinyl silane, and amino silane. Select the silane treatment that is compatible with the cure system to be used. Clay may be used in large quantities, is inexpensive, easy to incorporate, calender or extrude and provides some reinforcement to NBR compounds. 

Figure 4.2 Strange universes, (a) Tapping yourself on the back in a small, closed universe. (Drawing by Clay Fried.) (b) Like bubbles floating in the air, many separate n-dimensional worlds could exist if the universe were +/-dimensional. Could our universe be one of many separated in 4-D space If these spaces were to touch at some point, would we be able to communicate with an adjacent world (c) Your inside-out friend in a small, hyperspherical universe. (Drawing by Clay Fried.)... 

Statements 2 to 5. These were modified appreciably in the 1949 revision. In the earlier version, Clark believed that the properties of the water phase were very important in oil—sand separation, and he emphasized the role of air in floating the bitumen particles. In the later version, both these variables were given less emphasis. The critical factor was believed to be the association of clay with oil to form the somewhat mysterious flecks, which formed froth by submission to conditions to bring the flecks in contact with the water-air interface. In the body of the 1949 paper Clark left no doubt that convection currents were the mechanism not flotation in the normal sense of air-oil attachment. Clark backed up his new theory with some very revealing tests on simple clay-oil dispersions. Before discussing the merits of the two sets of statements, it would be of value to examine new data not available to Clark at that time. 

In carrier flotation, small-sized (several pm diameter) particles become attached to the surfaces of larger particles (perhaps 50 pm diameter, the carrier particles) [630]. The carrier particles attach to the air bubbles and the combined aggregates of small desired particles, carrier particles, and air bubbles float to form the froth. An example is the use of limestone particles as carriers in the flotation removal of fine iron and titanium oxide mineral impurities from kaolinite clays [630]. The use of a fatty acid collector makes the impurity oxide particles hydrophobic these then aggregate on the carrier particles. In a sense, the opposite of carrier flotation is slime coating, in which the flotation of coarse particles is decreased or prevented by coating their surfaces with fine hydrophilic particles (slimes). An example is the slime coating of fine fluorite particles onto galena particles [630],... 

In the flotation process, the powdered ore is mixed with water and a frothing agent such as pine oil. A stream of air is blown through the mixture to produce froth. The gangue in the ore, which is composed of sand, rock, and clay, is easily wetted by the water and sinks to the bottom of the container. In contrast, a copper sulfide particle is hydrophobic— it is not wetted by the water. The copper sulfide particle becomes coated with oil and is carried to the top of the container in the froth. The froth is removed continuously, and the floating copper sulfide minerals are recovered from it. 

The main application for this technique is in a system where the liquid feed contains fine solids that would block a fixed bed or tend to float resin out of a fluidized bed owing to the high density or viscosity of the feed. The process is used for the recovery of uranium from ore deposits containii a high proportion of clay minerals. Such ores produce a slimy pulp that is expensive to filter and thus there is an incemive to extract dissolved metal directly from the leach pulp. A number of plants were constructed in the 1950 in the United States on this principle—known as resin-in-pulp (RIP) operations. The simplest possible method of agitation, namely, to inject air into the base of the mixing tanks, was used in the early plants. ... 

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