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MICRONISED MICA It is produced in a special type of dry grinding machine that has no moving parts but depends on jets of high-pressure superheated steam which is capable of reducing the mica to ultrafine particles size ranging between 5 to 45 microns. This machine consists of a shallow circular grinding chamber into which minus 6mesh mica is fed continuously. High-pressure steam issued from orifices around the periphery of the chamber and set at an angle of the wall, keeps the mica rotating at a high speed. Grinding is accomplished by the innumerable collisions of the mica particles whirling at high speed. The steam is withdrawn at the center of the grinding chamber. As the mica particles become finer, centrifugal force no longer keeps them near the walls of the grinding chamber. The fine mica gravitates towards the center and drops into the chamber below through a conical bottom and discharged for bagging for marketing. Undoubtedly, it is the finest grade of ground mica, as well as, competitively cheaper as compared to wet ground mica. It is suitably used as a filler in paints and plastics. a)
MICRONISED MICA FOR PAINTS & COATINGS Micronised Muscovite Mica is extensively used as a pigment extender in various paints and coatings. It is a tough, flexible and transparent mineral that can be ground to less than a micron sieve mesh. b)
MICRONISED MICA FOR RUBBER APPLICATION It is used as an inert filler in rubber products. The use of mica helps to increase the hardness, tensile strength and tear resistance of rubber products. It improves the resilence and appearance of rubber articles. When used as a lubricant, mica particles form a continuous uniform film which effectively prevents undesirable adhesion of the rubber compounds to itself or the moulding surface. As a rubber compounding agent mica prevents massing and reduces gas penetration. It is used as a base in the moulding and tumbling of latex, synthetic foam and hose-pipes. The use of mica in the said applications is to eliminate the tendency to shrink. At the same time it helps to improve resistance in the sponge rubber goods. The use of mica permits expansion of the rubber in the mould during blowing without sticking. It is further used as a high temperature lubricant and flame-proof insulation for the manufacture and coating of PVC flexible insulating wires and cables. It is suitably used for both natural and specially coloured rubber articles, such as, bathing caps, costumes, toys, balloons, etc. The mica particles provide an attractive glossy-finish, as well as, a bright and sparkling appearance to rubber articles. c)
MICA FOR COMPOSITE PLASTIC SYSTEMS High-aspect-ratio muscovite mica is widely used as a reinforcing filler and extender in composite plastic systems because of its functional, morphological and surface characteristics. The addition of mica in plastic polymer compounds improves its material properties significantly, such as, higher heat deflaction temperature, increase tensile and flexural strengths, reduce isotropic shrinkage and permeability, enhance the dielectric, heat resisting and insulating properties, better surface properties, etc. In fact, mica is an unique mineral which offers the multiple advantage of high-respect ratio, high thermal stability and multi-directional lateral reinforcement to composite plastic systems. Besides, mica also offers plastic compounders a potential substitute for more expensive fiberglass reinforcements. No other products provide such functional enhancement to a wide range of plastic polymer compounds as superior quality and excellent dimentional stability than mica. WET GROUND MICA It is produced in mills of the chaser types. It consists of a cylinderical steel tank with a diameter of 6 to 10 feet and height of 3 to 5 feet. The bottom is lined with wooden blocks laid with the end grain up. Four wooden rollers of 2 to 3 feet in diameter and 1 to 3 feet across the faces revolve round a central shaft, at 13 to 30 r.p.m. These rollers are so fitted that they can be raised or lowered according to the height of the charge in the wall. Cleaned and washed mica scrap is fed into the mills, water is added and the rollers revolve at low speed and churn tha mass until the grinding is complete. After about 36 hours the water is siphoned from the settling tanks, the sludge is dewatered and dried either in steam-jacketed kettles or in a steam-heated drier. The dried product is sieved on multiple-deck vibrating screens, usually in 160 and 325 mesh, and finally bagged for marketing. Wet ground mica have a high metallic lustre or silvery sheen and is free from grit. However, it is a slow and costly process, and therefore, the product is relatively expensive. It is especially used as a pigment extender in paints, particularly in zinc-oxide paint and as a mould lubricant and dusting agent in pneumatic tyres as well as wall paper. COLOURED MICA They
are special-effects high-aspect ratio non-dispersing pigmentand fillers
derived from natural mica in carefully controlled process and designed
to impart granite-like appearances in most decorative coatings and thermoplastic
and thermoset resins. They are not a coated material. They can be easily
incorporated into plastic compounds, colour concentrates, liquid color
dispensions and dry color blends. They are resistant to chemicals, high-heat
and natural elements and endures consistency even when the most aggressive
production processes whose needs are not being met by current glitter,
metallic and coloured-filler compounds. MICA MANUFACTURING CO. PVT.LTD. 3C,
Camac Street, P.O.Box
9052, E-mail :mica@micamaf.co.in / mmc@micamafco.co.in
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