Calcium carbonate, ground

It is also made by precipitation from dissolved calcium hydroxide and carbon dioxide. The natural ground calcium carbonate and the precipitated material compete industrially based primarily on particle size and the characteristics imparted to a product. 

Natural ground calcium carbonate has been used for years as the primary constituent of putty. Since 1945, the processing of natural calcium carbonate has seen the introduction of beneficiation by flotation (qv) to remove impurities and the development of grinding processes to manufacture finer products. Precipitated calcium carbonate was first introduced in England in 1850 commercial production started in the United States in about 1913. 

The primary U.S. producers of ground calcium carbonate are Columbia River Carbonates, ECC International, Franklin Limestone Co., Genstar Stone Products, Georgia Marble Company, J.M. Huber Corp., Calcium Carbonates Division, James River Limestone Co., Inc., OMYA Inc. 

M. D. Stmtz and C. T. Sweeney, Natural Ground Calcium Carbonate, Proceedings Tappi Neutral jMlkaline Short Course October 1990, Tappi Press, Adanta, Ga., 1990. 

Non-reinforcing fillers (passive) Ground calcium carbonate (CaCO ) Reduce formulation cost adjust rheology, and mechanical properties. 

In the titanium dioxide production plant where the chlorine process is employed, the wastewater from the kiln, the distillation column, bottom residue, and those from other parts of the plant first settle in a pond. The overflow from this pond is neutralized with ground calcium carbonate in a particular reactor, while the scrubber wastewater is neutralized with lime in another reactor. The two streams are sent to a settling pond before being discharged. 

There are two sources of calcium carbonate, ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC). 

Ground calcium carbonate, extracted from the earth, is present in practically every country in the world in varying quantities in the form of limestone, marble, dolomite or chalk. Following the extraction, GCC needs to be ground. Dry grinding, the cheaper alternative, is often limited to a minimum particle size of 2- 3 microns. Wet grinding, more expensive, is used for fine and ultra fine material or when the final product must be a slurry (paper or paint application). Precipitated calcium carbonate is produced by chemical reaction between... 

A series of slurries of high solids, dispersed ground calcium carbonate were prepared. Firstly, a sample of Carrara marble was ground without dispersant to a mean size of 0.5 fim. This was then filtered to a solids level of 76% (volume fraction 46%), before being thoroughly mixed with the required dose of sodium polyacrylate dispersant and adjusted to a constant solids level of 70%. Doses ranged from zero to 25mgg (2.5%) of calcium carbonate. Samples were then left for two days to reach a steady-state adsorption level. After this they were sheared and their viscosity (Brookfield RV, 100 rpm, spindle 3) was measured. 

The hrst production step involves recovery of the metal from spodumene. The naturahy occurring ore, alpha-spodumene is heated in a brick-lined rotary kiln at a temperature between 1,075 to 1,100°C. This converts the alpha form to a more reactive form, beta-spodumene. The beta form is heated in a rotary kiln at 250°C with an excess of 93% sulfuric acid. The metal reacts with acid forming hthium sulfate. The kiln discharge is leached with water to separate water-soluble hthium sulfate from several impurity metals. Aqueous solution containing excess sulfuric acid is then neutrahzed by treatment with an excess of ground calcium carbonate (limestone). The solution is fdtered to... 

Fig. 1. Scanning electron micrograph of a typical ground calcium carbonate filler (courtesy of ECC International)...

CALCIUM CARBONATE. [CAS I3I7-65-3I- Calcium carbonate, [CAS. 471-34-11- CaCOi, mol wi 100.09. occurs naturally as the principal constituent of limestone, marble, and chalk. Powdered calcium carbonate is produced by two methods on the industrial scale. It is quarried and ground from naturally occurring deposits and in some cases beneftciated. It is also made by precipitation from dissolved calcium hydroxide and carbon dioxide. The natural ground calcium carbonate and the precipitated material compete industrially based primarily on particle size and the characteristics imparted to a product. 

The droplets crystallize and condense into hard, spherical prills that are dried, cooled, and sized for shipment. If calcium ammonium nitrate (CAN or nitro chalk) is made, ground calcium carbonate (limestone or dolomite) is added to the melt prior to the formation of the droplets when CAN is being made103 10S. 

DGEBA epoxy resin (EPON 828, Resolution Performance Products) Ground calcium carbonate (ExCal W3, Excalibar Minerals Inc.) Fumed silica (Cab-O-Sil TS-720, Cabot Corp.) BF3 amine catalyst (Leecure 8-239B, Leepoxy Plastics, Inc.) 50 48 2 1.5... 

Hydrocarb is also the trade name for a range of ground calcium carbonates made by Omya. 

Tensile strength properties of PVC-U, filled with precipitated and ground calcium carbonate, have been investigated (381, 404). 

Fillers. Fillers mentioned for epoxy systems (subsection 2.2.6.4) are used in polyurethanes too. Ground calcium carbonate (coated as well as uncoated) is commonly used. Barium sulphate, silica fumes, wood flour and milled glass fibres are also used. 

The concept of lower water vapor permeability has been tested in comparison to a silicone based RTV-2 system (Elastosil SG 500 from Wacker Silicones) according to DIN 53122-1 (samples were 2 mm thick). The Poly bd RT 45 HTLO-based sample also contained ground calcium carbonate as a filler. It can be clearly seen that the overall permeability is significantly lower for the novel RTV-2 system. 

Unsaturated polyester resin Glass fibers Ground calcium carbonate ... 

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