DSM was at that time very active in developing new synthetic products and particularly saw growth opportunities with EPDM. DSM developed this EPDM and gave it the brand name Keltan. In the search for manufacturers who could develop this semi-finished product to a complete construction product, DSM earmarked several producers, (mainly in tires and profiles), to possibly partner with.
The experience Hertel had with the production of a homogeneous film, made of rubber (Butyl), eventually proved decisive in DSM choosing them to partner with. Cooperation between the two R & D departments in 1968 led to the first EPDM membrane being produced. The EPDM roofing material was put into the market under the name Hertalan, which is a combination of the words Keltan and Hertel.