In another chemical reaction, vulcanization, the loose chain molecules of the rubber are combined with one another. It is only at this stage that the sticky raw material turns into rubber as we know it. However, vulcanization of butyl rubber can be a lengthy process because the material only contains a few “anchor points” for linking the molecules. In a subsequent step, chemists therefore add chlorine and bromine atoms to the chain molecules, as these produce outstanding anchor points for vulcanization. These also ensure that the new “quick” butyl rubbers can be easily combined with other grades of rubber – making them ideal for airtight inner liners in car tires, which have to interact with other rubbers.

However, LANXESS is one of the few companies which can master this process of “halogenation”, which constitutes an extremely complex reaction. Nevertheless, “halobutyl rubbers” have now become so important that they have replaced their predecessor in many cases. More than 80 percent of butyl rubbers from LANXESS now have “halo” in their name. Taken together, they generated sales of more than EUR 500 million in 2007.