Wacker Chemie and Dow Corning Siloxane and Pyrogenic Silica Production Facility, China

Wacker Chemie and Dow Corning's integrated silicone manufacturing facility is the largest and most advanced facility in China. It was built at a cost of $1.2bn and is located in Jiangsu Yangtze River Chemical Industrial Park in Zhangjiagang City, China. The city is one of the fastest-growing regions in China and is situated 170km outside Shanghai in Jiangsu Province.

Construction of phase one of the facility began in 2006 after receiving approval from the Chinese government. The facility started its operations in November 2008. The silicone manufacturing facility consists of a pyrogenic silica plant and a siloxane plant and covers an area of 1km². The production capacity of the facility is estimated at about 100,000t/y.

The manufacturing facility utilises two primary raw materials – silicon and methanol. These raw materials are mostly sourced locally, resulting in cost savings. Wacker and Dow jointly own and operate the facility. Marketing and sales of the finished products is carried out independently by the two companies. Other companies situated in the industrial park form part of the facility's complex production chain.

"The expansion is expected to increase the production capacity of the siloxane and pyrogenic silica plants to approximately 210,000t/y."

Silicone facility expansion

On 21 October 2009 Wacker and Dow started construction of the second phase of the pyrogenic silica plant. The expansion is expected to increase the production capacity of the siloxane and pyrogenic silica plants to approximately 210,000t/y. The exact amount of investment was not revealed but is estimated to be in the double-digit million euro range.

With the demand for siloxane and pyrogenic silica increasing rapidly, the expansion is expected to help the two companies widen their customer base and aid in the growth of the silicone industry in China.

Process technology

The pyrogenic silica plant heats the raw material chlorosilane through hydrolysis at temperatures above 1,000°C. After being heated, chlorosilane produces pyrogenic silica and hydrogen chloride (HCL). The HCL produced is supplied to the siloxane plant. Pyrogenic silica produced through the process mechanically fuses on cooling to produce agglomerates or tertiary structures. These structures are 1–250mm in size.

The basic raw materials used to manufacture silicones are silicon and methyl chloride. A direct reaction between silicon and methyl chloride produces methyl chlorosilanes. Chlorosilane is distilled to produce dimethyldichlorosilane, which is further hydrolysed to produce polydimethylsiloxane (PDMS).

One of the unique features of the facility is its integrated production system. The siloxane plant provides chlorosilane as feed to the pyrogenic silica plant for producing pyrogenic silica. The pyrogenic silica plant returns the by-product HCL back to the siloxane plant for the production of siloxane. The system uses statistical process control and highly effective reactor dynamics.

The integrated nature of the production system ensures that high-quality pyrogenic silica is produced, and generates less waste and reduces emissions. The integrated system also reduces logistics costs, thereby improving the facility's efficiency.

Silicone and silica products

"The facility manufactures more than 3,000 silicone products and pyrogenic silicas."

The facility manufactures more than 3,000 silicone products and pyrogenic silicas. Pyrogenic silica is used in printing inks, insulating gels, adhesives, paper coating and grouting compounds. It is also used in natural and synthetic rubber for reinforcement, for stabilisation in textile impregnation and in accumulators.

Silicones have distinct surface characteristics such as low surface tension. The characteristics make them ideal for use in paper release agents, construction, water repellents, cosmetics and textiles.

Site location

Wacker and Dow chose to locate the facility in China due to its rapid pace of development. In addition, the chemical park provides unique advantages such as excellent port facilities, government cooperation and support and access to quality local talent.

The Asian region is also being considered as a potential market for future growth. China has the second-highest demand for silica in Asia.