FUMED SILICA – A BOON FOR INVESTMENT

Fumed silica, also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Its three-dimensional structure results in viscosity-increasing, thixotropic behaviour when used as a thickener or reinforcing filler.Fumed silica is a collection of very-fine non-porous particles.     

         PHYSICAL DESCRIPTION:

Fumed silica is composed of submicron-sized spheres, which are 40-60% fused into short chains, very highly branched, 0.1-0.2 microns long. The spheres are quite uniform in size for a given product, but the chain lengths are quite variable, 10 to 30 units in length. The surface area, which varies with the particle size, gives a good approximation of the sphere diameter. The smaller the particles, the larger the estimated surface area.²

^{APPLICATIONS OF SILICA}

·         Adhesives

·         Sealants

·         Plastics

·         Inks

·         Paints

·         Coatings

·         Defoamers

·         Toner

·         Silicone Rubber

·         As a thickening agent

·         An anticaking agent (free-flow agent) in powders. Like silica gel, it serves as a desiccant.

·         It is used in cosmetics for its light-diffusing properties.

·         It is used as a light abrasive,

·         in products like toothpaste.

·         Other uses include filler in silicone elastomer and

·         viscosity adjustment in paints, coatings,

·         printing inks,

·         adhesives and unsaturated polyester resins

Typical applications areas

• HTV-Silicone Rubber

• Extruded Parts

• RTV-Silicone Rubber

• Moulding Compounds

• Sealing Compounds

• Casting Compounds

• Liquid Silicone Rubber

• Extruded Parts

• Injection Mouldings

• Synthetic Rubber

• Cable Insulation

• Sealants

Grade

*              Untreated grade (Hydrophilic grade)

*              Treated grade (Hydrophobic grade) Untreated grade

Numerous grades of hydrophobic fumed silica have been developed to solve particular technical problems.  Hydrophobic fumed silica are produced by chemical treatment of hydrophilic grades with silanes or siloxanes.

Applications:

Paints, inks, adhesives, plastics, coatings, toners, defoamers, silicone rubber, silicone sealants, cosmetics, agriculture, fire extinguishers, foods, polyester resins, cable gels, greases, etc.

Positive effects:

·        Optimum rheology during processing

·        Thickening of polar liquids, e.g. epoxy resins

·        Reinforcement of silicone elastomers

·        High levels of loading, e.g. molding compounds

Treated grade

Positive effects:

·         Optimum adjustment of rheology during processing

·         Reinforcement of silicone elastomers

·         Thickening of non-polar liquids

·         Free-flow of foodstuffs and industrial powders

·         High chemical purity

METHOD OF PREPARATION:

Silicon tetrachloride is burned in a flame of hydrogen and oxygen (at approximately 1800EC) to produce molten spheres of silicon dioxide (and hydrogen chloride). Depending on process parameters, the size of these silica spheres can be varied and, within a given batch, show excellent uniformity (by electron micrograph). The molten spheres collide and fuse with one another to form branched, three-dimensional chain-like aggregates.

Many aggregates have chains from 10 to 30 spheres in length, or from 0.1 to 0.2 microns ( in length. As the aggregates cool down below the fusion temperature of silica (approximately 1710EC), further collisions result in some reversible mechanical entanglement or agglomeration. Further agglomeration occurs during the collection process; this can be reversed by proper dispersion in a suitable medium.

During the formation of the product, hydroxyl groups become attached to some of the silicon atoms on the surface of the silica particles, making the surface hydrophilic and capable of hydrogen bonding with suitable molecules. There are (estimated) 3.5-4.5 hydroxyl groups per square millimicron of silica surface, compared to a theoretical maximum of 7.85. The structure of fumed silica is amorphous (as indicated by absence of lines in its X-ray diffraction pattern.)

Indian demand for fumed silica

Fumed silica is used in India in cross section of industries including the following:

·         Paint and coating

·         Printing ink

·         Toners

·         Resin

·         Cosmetics

·         Rubber

·         Pharmaceutical

·         Adhesives/sealants

·         Miscellaneous

Fastestgains for fumed silica will be in the electronics sector due to advances in the use of CMP. CMP demand for fumed silica is expected to grow ro­bustly over the forecast period, es­pecially for high purity grades. Plas­tic and coating applications for fumed silica will also record gains as the economy expands.

Growth rate in demand:

Global demand to rise 6.3% annually through 2014

World demand for specialty silica -- which include precipitated silica, fumed silica, and silica geland silica sol -- will rise 6.3 percent per year to 2.7 million metric tons in 2014. This pace of growth represents acceleration from the 2004- 2009 period, in which silica demand was hampered by a global economic recession. Gains will be driven by a rise in world manufacturing activity, particularly in key silica markets such as tires, rubber, chemicals and agricultural products.

Global scenario

Global production/ demand

World demand for specialty silica -- which includes precipitated silica, fumed silica, silica gel, and silica sol -- will increase at a healthy pace to 2.7 million metric tons in 2016. Robust growth in rubber applications -- the largest market for specialty silica -- will drive gains, particularly in the expanding industrial sectors of developing countries such as China and India.

Strong turnaround in rubber industry to benefit specialty silica consumption

Through 2016, the fastest gains in volume terms will be seen for fumed silica, fuelled by a rebound in the production of silicone rubber for industrial rubber applications as the economy recovers. Precipitated silica demand will also be bolstered by strong gains in nontire rubber products.

Important producers and their production share

Evonik

Evonik, the creative industrial group from Germany, is one of the world leaders in specialty chemicals. Its activities focus on the key megatrends health, nutrition, resource efficiency and globalization. Evonik benefits specifically from its innovative prowess and integrated technology platforms. Evonik is active in over 100 countries around the world. In fiscal 2011 more than 33,000 employees generated sales of around €14.5 billion and an operating profit (adjusted EBITDA) of about €2.8 billion.

Apart from precipitated silica, Evonik produces AEROSIL®fumed silica and silica-based matting agents.

Overall, Evonik has a global capacity of around 500,000 metric tonnes per annum for precipitated and fumed silica as well as matting agents.

Wacker

Wacker Chemie has announced plans to consolidate its fumed silica production in Germany at its Wacker Silicones division.

The company has transferred its Kempten, Germany fumed silica manufacture to Burghausen and Nuenchritz, Germany. The Kempten site was closed in 2011.

Joint venture in China

Wacker has set up a joint venture at Zhangjiagang, China, in which Wacker has share of 51% and Dow Corning 49%.

Cabot

Cabot currently has six fumed silica manufacturing facilities globally, including two in the United States (Tuscola, and Midland), two in Europe (Barry, Wales and Rheinfelden, Germany), and two in Asia (Jiangxi Province, China and Mettur, India).

CAB-O-SIL ULTRABOND 4740 fumed silica reduces fumed silica processing time by up to 50 percent during the manufacturing stage, compared to competitive products in the market. This feature substantially reduces the total cycle time and creates the added benefit of improved asset productivity

Scenario in China

In China, demand for these materials is still growing strongly due to string growth in the end-uses, including rub­ber products such as sports shoes, tires, automotive and industrial parts. The de­velopment of niche end-use markets in the electronics, rubber and other indus­tries served by specialty silica produc­ers has otherwise helped to sustain over­all growth levels in China and overseas. In order to sustain the growth and prof­itability of their specialty silica business units, some producers of these materials have broadened their product offerings through acquisitions and new product development efforts.

Shenyang Chemical Co Ltd plans to expand fumed silica capacity to 5 000 metric tonnes per annum.

5 000 metric tonnes per annum fumed silica unit constructed by Chongqing Wanzhou Industrial Zone was put into operation in 2011.

Other producers include the following:

*              Xinjiang TBEA Silicon Industry Co Ltd,

*              Jilin Shuangji Chemical New Material Co Ltd,

*              Zhejiang Wynca Chemical Industry Group Co Ltd

*              Shandong Ruiyang Silicon Industry Technology Co Ltd

By 2015, China's fumed silica capacity is expected to reach nearly 100 000 metric tonnes per annum.

Prognosis:

Demand for fumed silica is expected to be healthy, benefiting from gains in small volume markets such as plastics, adhesives and sealants, cosmetics and toiletries and food and drinks. Growth would take place in large electronics market, where it finds use in chemical mechanical planarization slurries.