Chlorine’s role in industrial processes

Chlorine is essential to Europe's chemical industry, with 55% of all chemical processing depending on this element. It allows the efficient use of raw materials and energy in the production of numerous compounds which would be difficult or impossible to synthesise using other pathways.

Chlorine and some chlorinated derivatives are excellent synthesis intermediates because of the high reactivity of the carbon-chlorine bond.

Two of the most widely-used groups of engineering materials, polyurethanes and polycarbonates, are produced with the help of chlorine. Chlorine is used as a reactant for the synthesis of intermediates and is normally not present in the final products. Often, the chlorine is recycled.

Polyurethane

Polyurethanes are extremely versatile plastics. They can be as soft as a sponge or as hard as stone. They come in the form of moulded parts or films, fibres or colourful coatings.

Polyurethane rigid foam is the most widely used insulation material for refrigeration units in Europe, the US and the Far East. This is because rigid foam insulates better than any other material. in refrigeration and construction, polyurethanes are THE big energy savers, thus also limiting CO2 emissions from power generation.

The furniture and mattress industries are the main users of polyurethanes. They are also in the soles of trainers and the insides of skis. They are also in surfboards, skateboards and tennis rackets.

Polycarbonates

Chlorine is used to make polycarbonates, the plastics vital to producing crystal-clear sound in CDs and huge information storage and transmission facilities on DVDs. Polycarbonates are also used to make shatter-resistant streetlight covers, traffic lights, car headlights and computers.

Silicones

Chlorine chemistry is also used in the synthesis of silicones, made from chloromethane and silicon which react to give chlorosilanes. These are then hydrolysed and polycondensated in polysiloxanes, better known as silicones. Used in the form of fluids or technical components they have valuable properties such as lubrication, electrical insulation, chemical inertness and thermal stability. They are used in all industrial sectors, especially those demanding high-quality materials such as surgical materials such as implants, catheters and drains.

Silicone fluids are used as refrigerants in freeze-drying facilities that operate in a vacuum at temperatures of -50°C. This allows water to be extracted from biological substances such as units of blood, serum, bacteria and viruses without damaging them. They are also used for therapeutic purposes such as in ointments to protect the skin. Life-saving artificial cardiac valves are made from silicone rubber.

Various alternative processes have been studied, particularly for isocyanates, silicones and polycarbonates. However, they have been found to be less reliable and of lower performance than processes using chlorine.