Calcium carbonate product selection

Synthetic Marble. Synthetic marble-like resin products are prepared by casting or molding a highly filled monomer mixture or monomer—polymer symp. When only one smooth surface is required, a continuous casting process using only one endless stainless steel belt can be used (52,53). Typically on the order of 60 wt % inorganic filler is used. The inorganic fillers, such as aluminum hydroxide, calcium carbonate, etc, are selected on the basis of cost, and such properties as the translucence, chemical and water resistance, and ease of subsequent fabrication (54,55). 

Calcium carbonate is one of the most common filler/extenders used in the paint and coatings industry. Consumer and contractor paint formulas can include products from submicrometer size to coarse mesh sizes. The main function of calcium carbonate in paint is as a low cost extender. It is also used to improve brightness, appHcation properties, stabiHty, and exposure resistance. Coarse products help to lower gloss and sheen or even provide textured finishes. The selection of product type and particle size is deterrnined by the desired performance and cost of the coating. 

Changing catalyst support from carbon to calcium carbonate leads to dramatic improvement of the cis/tran ratio from 6 1 to 18 1, that is the cis selectivity increases from 85.7% to 94.7%. The reason for better selectivity on CaC03 supported catalyst is attributed to its lower surface area leading to lower hydrogenation activity, but more selective to the desired product. The successful commercialization of the new route for sertraline synthesis demonstrates that for a stereoselective hydrogenation reaction, improve product selectivity can be achieved by proper selection of catalyst support. 

Elemental composition Ca 50.03%, C 14.99%, N 34.98. A measured amount of the compound is hydrolyzed with water. The product CaCOs is filtered, dried and determined by gravimetry. Calcium carbonate or the parent calcium cyanamide may be digested with nitric acid, diluted appropriately, and analyzed for Ca by AA or ICP spectroscopy. The hydrolysis product in solution, ammonia, may be measured by ammonium ion selective electrode, or by colorimetry followed by Nesslerization. 

With most hydrogenation catalysts of the platinum and nickel groups (Sections 4.2.61, p. 459 and 4.2.50, p. 450), a mixture of products is obtained even if an attempt is made to stop the reaction at the half-way stage. An alkene may only be obtained in good yield if particular attention is paid to the selection of a deactivated hydrogenation catalyst. An early, highly effective formulation of a deactivated palladium catalyst is Lindlar s catalyst (Section 4.2.54, p. 453), but palladium-on-barium sulphate in the presence of quinoline, or palladium-on-calcium carbonate, is also recommended. In these cases it is advisable to... 

Several chemical reactions, including calcium carbonate and hydroxyapatite precipitation, have been studied to determine their relationship to observed water column and sediment phosphorus contents in hard water regions of New York State. Three separate techniques have been used to Identify reactions important in the distribution of phosphorus between the water column and sediments 1) sediment sample analysis employing a variety of selective extraction procedures 2) chemical equilibrium calculations to determine ion activity products for mineral phases involved in phosphorus transport and 3) seeded calcium carbonate crystallization measurements in the presence and absence of phosphate ion. 

Gorecki DKJ, Richardson CJ, Pavlakidis P, Wallace SM. Dissolution rates in calcium carbonate tablets a consideration in product selection. Can ] Pharm 1989 122 484 87, 508. 

Calcium carbonate does not have functional groups (its surface is inert), therefore interaction can only be improved by chemical modification. Some hydroxyl groups can be found from admixtures such as Ca(OH)2 but these admixtures may limit the ways in which calcium carbonate can be used because these admixtures increase the amount of absorbed moisture. Functional groups are frequently hydrophilic thus they attract water molecules. In many applications, moisture can either cause product instability, reduce cure rate, or reduce reinforcement. Caution is needed in selecting surface treatment to generate functional groups. 

Fillers are used in these products to improve mechanical properties or impart flammability resistance. Fillers are frequently silane-treated to further improve mechanical properties. Fillers must have a low moisture (below 0.1%), a low absorption of resin, and are expected to impart thixotropic properties. There are special cases. For example, if peroxyketals are used as initiators, basic fillers have to be used because acidic fillers interfere with cure times and the shelf-life of the composition. Shape and particle size distribution must be considered in filler selection to impart the desired rheological properties. Calcium carbonate is the most popular filler but aluminum trihydrate, anhydrous calcium sulfate, and silica are also frequently used. Barite is well suited to this application, especially if acid... 

Commercial products can be recommended by homoeopaths or self-selected by patients for well-recognised conditions even though this might not be approved of by classical homoeopaths. Popular remedies would include Arnica for bruises. Thuja for verrucas and warts. Calcium Carbonate for rheumatism. Sulphur for indigestion. Belladonna for headache, Pulsatilla for cystitis and Bryonia for constipation. 

Among the simple catalysts that have been proposed oxides of zinc,09 cadmium, lead, bismuth, silicon, aluminum, titanium may be mentioned.5,0 Alkaline materials as sodium or calcium carbonates have also been claimed. The zinc oxide catalyst is prepared by spraying a solution of zinc nitrate, alone or with nitrates of other metals, on pumice and then heating the product in air. In practice the phthalic anhydride is simply steam dis-stilled into the reaction chamber and the products separated by fractional condensation or selective solution. 

The design of highly selective catalysts for the hydrogenation of dienes and alkynes is an important problem. Among the transition metals palladium is well known as being the most selective of all for the production of mono-olefins. This selectivity can even be improved when doped, as in the so-called commercial Lindlar catalyst which is composed of palladium and lead supported on calcium carbonate. There is still a need for stable and highly selective catalysts, especially at high conversion. 

A representative selection of commercial color concentrates (Colortech Inc, Brampton, ON) were used for this study. Each pelletized sample consisted of a blend of organic and inorganic pigments dispersed in Linear Low Density Polyethylene (LLDPE) carrier resin. Pigment loading varied between 3,6 and 50.0 wt,% and some formulations contained up to 33.1 wt.% calcium carbonate filler. All were prepared on a production-scale 40 Liter Gelimat-style... 

Reinforcing fillers used are carbon black and non-black fillers such as silica, clay, and calcium carbonate although the latter two are used more in lower cost industrial applications and not in tires. Protectant systems consist of antioxidants, antiozo-nants, and waxes. The vulcanization system essentially ensures that the optimum mechanical properties of the polymer system are achieved. Finally, the tire compound can contain various miscellaneous materials such as processing aids and resins. The materials scientist when designing a tire compound formulation has a range of objectives and restrictions within which to operate. Product performance objectives define the initial selection of materials. These materials must not raise environmental concerns, be processable in tire production plants, and be cost effective for the end user [4]. 

Unsaturated monomers have been adsorbed on to fillers and then polymerised to give encapsulated products. The modulus of the polymer could be modified by selecting the monomer [40]. Acrylic acid-vinyl chloride (1 99) has been polymerised on to calcium carbonate [41] reports of the use of 3,5-triacryloxyhexahydro-S-triazine [42], bis-phenol A and epichlorohydrin [43], methyl methacrylate [44], and acrylic acid [45] have also been published. 

It is very well documented that the carbon-carbon triple bonds (e.g., alkynes) on catalytic hydrogenation gives the completely reduced product, viz. alkanes. Alkynes can also be reduced partially to give z-alkenes by palladium-calcium carbonate catalyst which has been deactivated (partially poisoned) by the addition of lead acetate (Lindlar catalyst) or Pd-BaSO deactivated by quinoline. The lead treatment poisoned the palladium catalyst, rendering it less active and the reaction is more selective. Some examples are given (Scheme 98). 

In mutagenesis the main condition of success is the development of a sensitive and rapid method of mutant selection. Vitamin B12 production by propionic acid bacteria correlates with acid production. But the method of selection based on picking colonies with the maximal diameter of dissolution zones of calcium carbonate (added to solid medium) did not give positive results, since the size of colonies is not identical while acid production is dependent on the quantity of biomass. Selection based on the intensity of pink color that correlates with vitamin B12 production has a disadvantage in that selection of small mutations is made step by step, when differences in color can hardly be noticed by eye. Another method used was based on direct determination of vitamin B12 in single colonies. This method is labor-intensive and severely limits the testing of large numbers of colonies. 

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