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The epithet , "White Carbon" is earned by Precipitated Silicas (White
Powder) manufactured by wet process, as these materials give a whole new spectrum
of opportunities to Rubber Compound with respect to the coloring of products
and that too, without serious loss of physical or chemical properties.
Although the first attempts to use white fillers were made as early as 1930,
it was after another 20 years that silica produced by precipitation (In Europe)
could yield rubber products with performance that could be comparable with standard
Carbon Black reinforced compounds.
In India, attempts to manufacture Precipitated
Silicas, matching the quality
of leading German companies like Degussa, Buyer etc. were made in early 80's
but not with much success. In the year 1983, Kadvani Chemicals, after a research
of about 18 months could get a quality product matching the then Imported
Silicas.
They started the commercial production of precipitated Silicas immediately and
very soon they were able to get a proud place in the Indian market for their
products, which they branded as Kad-Sil.
General Process :
Precipitated Silica is manufactured by Wet Process, using Alkali Silicate Solutions,
preferably Sodium Silicate (Water Glass), as a starting material. Silica is
precipitated from this solution by the addition of a mineral acid, viz.
Sulphuric
Acid. The precipitated Silica is filtered and washed free of salt, which is
obtained during the precipitation by the reaction between Sodium Silicate and
the acid.
Process I : Pre-Synthesis :
It is a process in which sodium silicate solution is made from sodium
silicate (Water
Glass).
Process II : Synthesis :
Synthesis of Kad-Sil
is the first major stage of the process which is carried
out in Acid Resistant Reactors, during which, Silica is obtained in the precipitated
form, by the reaction of Sodium Silicate Solution and a mineral acid viz. Sulphuric
Acid. Temperature and Ph of the solutions are but a couple of major parameters
out of several others, which are critically controlled by automization in
instruments to obtain various grades of consistent quality precipitates.
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Process III -
Filteration and Washing :
The suspension of Precipitated Silica derived during the synthesis, contains
salt impurities - a result of the reaction between sodium silicate and sulphuric
acid - and which has to be removed to get the pure final product.
The suspension is passed through a Filter Press, where the
precipitated Silica
form a cake. This is washed free of salt during this process, and the pure wet
cake is then ready for drying.
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Process IV : Drying :
 The wet cake of precipitated silica, has a solid contents of about 20 percent
by weight, the rest being the water, which has to be removed by evaporation,
a process, which accounts for a large proportion of total production costs.
At Kadvani Chemicals Private Limited, this is done in a Spin Flash Dryer, a
fully automatic drying system, assuring a good consistent quality Final Product.
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Process V : Milling and Packing :
 The dried Kad-Sil, is then milled, where it is reduced to its required particle
size and packed in air tight bags.
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Other Requirements :
We also manufacture Tailor made Precipitated Silicas, as per your specifications,
provided your requirements is substantial and regular.
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