CEH Report

Table of Contents

Abstract

This report covers sodium and potassium silicates and silicas and silicates derived from sodium silicate—precipitated and colloidal silica, silica gel, and calcium and magnesium silicates. It also includes two other specialty amorphous silicas—fumed and fused—and ethyl silicate, which is used in markets similar to those of colloidal silica. In addition to being used as sources of buffered alkalinity and corrosion protection, soluble silicates find use as binders, as do colloidal silica and ethyl silicate. A number of the silicas and precipitated silicates—precipitated, gel and fumed silica, and calcium silicate—are used as specialty fillers, carriers and flow-control agents.

Precipitated and colloidal silicas (silica sols) and silica gels are usually produced commercially from sodium silicate. These derivative silicas are amorphous (noncrystalline) and water insoluble, characterized by different physical properties such as surface area, particle size, pore size and shape. These silicas are commercially available in a variety of grades suited for many different industrial applications.

Increasingly, the major producers of these products are participating in global markets. A number of mergers and acquisitions have occurred in recent years. The downturns in worldwide economic activity in the last few years have resulted in less-than-anticipated growth in the silica industry, particularly in Europe and the United States. Reduced demand coupled with rising energy and raw materials costs have negatively impacted the chemical industry. Lower costs of production in China and other Southeast Asian countries have also resulted in a number of plant closures in recent years in developed countries. The silica industry, although experiencing a decline in demand for semiconductor applications, was helped by demand from sectors like toothpaste and rubber for footwear (specific to Asian economies), which are relatively unaffected by recession.

In addition to a variety of direct uses, sodium silicate is consumed in the downstream production of derivative silicates, precipitated silicas and aluminosilicates including zeolites. Precipitated, colloidal and gel silicas are all made from sodium silicates. These derivatives account for a substantial percentage of total silicates production.

Laundry detergents represent the largest single market for sodium silicates in most regions when both direct use (where the silicate serves as a builder and as a source of alkalinity) and indirect use (where the silicate is used as a raw material for detergent zeolites) are considered. Another important direct-use market is in pulp and paper, where sodium silicate is used primarily to stabilize hydrogen peroxide in pulp bleaching and for deinking of recycled paper.

Potassium silicate is used as a binder in welding rods and in several other markets. It is also used as a detergent builder in both consumer and industrial/institutional products, and in various water-based coatings for the construction industry. Calcium silicates are amorphous, water-insoluble powders precipitated from sodium silicate solutions, which function as specialty carriers (especially of oils), flow-control agents and fillers.

In contrast to sodium silicates, which are commodity chemicals, silicas are relatively high-value specialty products. Projected growth rates for consumption of these specialty silicas are typically higher than those for sodium silicates. Several of the specialty silicas have overlapping properties and are used as fillers, binders, carriers and flow-control agents in a wide variety of high-performance applications.

One area where silica is growing rapidly is in use as a substitute for carbon black as tread filler, where it can result in up to a 20% reduction in rolling resistance corresponding to around 5% in fuel savings. The "green tire" industry accounts for about half of the demand for precipitated silica. U.S. growth is expected to be around 5%, although Chinese demand is expected to catch up later.

Precipitated silica is the largest-volume specialty silica. Its largest market is as a filler for rubber, primarily for automotive tires, and also for footwear. Other important end uses include batteries, food and health care products, and agricultural products. China is currently the world's largest automotive market, ahead of Japan and the United States. It is expected to account for almost 40% of the precipitated silica market in Asia in the next five years.

Silica gels are used in some food and health products, in the more demanding carrier/adsorbent/desiccant applications, and as high-quality thixotropic agents in paints and coatings. The major market for fumed silica is as a reinforcing filler in silicone elastomers. Fumed silica is also used in more demanding carrier/adsorbent/desiccant applications and as a high-quality thixotropic agent. Fused silica is used in investment casting, as a specialty filler in refractories, and as a filler for epoxy resins in electronics packaging.