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by Dmitry TARASOV, Cand. Sc. (Chem.), Baikal Minerals Group, Deputy Director General; Irina KULESHOVA, laboratory head, ОАО R.&D Firm Spektr Lakokraska (Paintwork Spectrum)
Broadening the raw materials base is still in the mainstream here in this country. The proportion of imported ingredients in our paintwork products keeps high, and that makes us very sensitive to the market situation and currency fluctuations. The consumer qualities of our domestic raws, too, still leave much to be desired.
Mineral fillers are an essential part of paintwork products. Such filling agents can make up as much as 50 - 70 percent of the finished items. Conversely, the amount of pigments and coloring agents goes down. As industrialized countries shifted to the wide-scale production of finely dispersed substances, something that wrought dramatic changes in formulation standards, we in Russia still stuck to the low-cost filler, chalk.
Elsewhere in the world the industry is using a wide mix of finely dispersed cost-effective minerals en-suring the required physico-chemical, protective, decorative and other standards of paint coating. In a way, the very word filler, or filling agent, has become obsolete, defunct there-instead, one opts for the pigment extender. Well, the implication is clear enough. In fact, our country is rich in minerals that could be utilized as pigment extenders. But only a few have been selected thus far.
East Siberia (Irkutsk oblast and Buryatia) holds out the best promise. True, it lies far from potential consumers; however, deposits are situated near the Trans-Siberian trunk railroad, and they are quite competitive, since the quality of local ores allows to do without flotation (dressing and separation) and further beneficiation.
Deposits of white pigment extenders in Russia.
Relatively low-cost electric power is an added advantage.
Located in the Northwest (Karelia and Kola peninsula) are Kovdor (phlogopite, amber mica) and Chupa (muscovite) deposits, along with talcum magnesite with the variable presence of iron and other impurities. Hence flotation is needed to make such raws satisfy commodity standards. Although these deposits do not lie far from prospective consumers in this and other countries, the nearest railroad line is but 100 - 150 km away.
The Ural belt (Chelyabinsk and Sverdlovsk oblast, Komi Republic)* can also cater to our industry. These regions have a far-flung transportation network as well as many processing enterprises. Unfortunately local ores are much depleted and need flotation.
Our experts do not rule out wide-scale exploration of minerals in South Siberia (namely at Kemerovo, Altai, Krasnoyarsk, Khakasia), too. However, these lie far from potential markets and have poor transportation facilities, not to speak of the absence of adequate industrial facilities (for drying, baking and clearing talcum-tremolite ores) from quartz admixtures.
Up-to-date equipment and its proper maintenance is an essential part of our industry. All kinds of mills (roller, ball, rotor ones) that we have inherited from the Soviet times do not ensure the required granulometric standards despite their high productivity. What we need is jet-type (air-stream) rotor mills used abroad: these crush minerals with compressed air fed at high pressure, which accounts for the high homogeneity and stable quality of the end product.
The world output and consumption of paintwork materials totals 25 mn tons, with as much as 900,000 tons in Russia. In our humble opinion, the paintwork industry could boost output by zeroing in on the production of proper fillers (pigment extenders), for these agents have a significant effect on the quality of paints and are far less expensive than other components. That's how we can upgrade the quality of our products.
Talcum is one of the most used fillers capable of impacting the decorative, physicomechanical, technological and service properties of paint coats. The talcum crystal lattice is formed by a magnesium oxide layer fringed by two layers of nonpolar quartz tetrahedrons and oxygen atoms. The outer surface of this material's particles in the scaly, lamellar form contains no hydroxyl groups and active ions, which imparts high chemical inertness and hydrophoby (water-repellency) to talcum. The three-layer
* See: V. Chereshnev, "Science-Key Development Factor of Ural", Science in Russia, No. 5, 2003. - Ed.
Deposits ranked in order of talcum efficiency in alkyd enamels.
talcum crystals, though solid in structure, are not tightly bonded, which ensures such physicome-chanical characteristics of fillers as softness, "slip", rigidity and ready crushability.
Talcum is indispensable in the production of the two heaviest paintwork materials, the alkyd and water-disperse ones. This pigment extender controls the viscosity of materials, diminishes paint runs, delamination and sagging; it enhances the atmospheric and corrosive resistance of paint coatings, and offers diverse decorative properties, from glamor to opaque.
Talcum seldom occurs as a monomineral deposit. It is found in the scaly dense mineral steatite remarkable for lamellar particles, chemical inertness and hydrophoby. We have only one deposit of this mineral-at Onot in the foothills of the Eastern Sayany (Irkutsk oblast).
Talcum is often associated with chlorites, serpentinites, and tremolites. We in Russia have two deposits of talcum/tremolite*, known also as "stringy" or "spicular" ("needle-shaped") - at Algui and Kirghitei. Combined with tremolite, talcum improves the mechanical characteristics of polymer coatings at the expense of their protective and decorative properties.
But the commonest impurities in talcum ores are the carbonates-magnesites, dolomites, cal-cites (Middle and South Urals). The efficiency of these filling agents depends not so much on the mineral characteristics of the raw material as on appropriate flotation.
To assess the effect of the basic raw material on the quality of paintwork products we have tested pigment extenders produced from ores of different deposits. We have studied rheological** characteristics, dispersal (grinding) kinetics, paint runs, coating luster and brightness, resistance to ultraviolet and water. Paints filled with talcum-steatite from the Onot deposit have proved superior.
Our investigations invite this conclusion: all filler grades produced by BAIKAL MINERALS Co., especially the ultradisperse Talcon MM-10, perform well in alkyd enamels and in materials developed on the basis of other filmforming agents, water-diluted too. Quite on a par with import analogs, they are much superior in certain technical characteristics as well.
Journal "Paintwork Materials, Their Application", No. 9, 2004
* Mineral from the amphibole group with hardness index 6 on the Mohs' scale. - Ed.
** Rheology is concerned with the fluidity and deformation of real solid media possessing viscosity, elasticity ad plasticity - Ed.
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