Whether it’s a hose, profile, conveyor belt or handrail – the quality and durability of elastomer products are based on the right rubber compound. At Semperit, mixing is done in-house at several locations in Europe and Asia and comprises around 100,000 tonnes per year. This corresponds to an 80-centimeter-wide carpet runner extending from Vienna to Beijing.
“At the beginning, every Semperit product looks the same. We have the cradle of Semperit here, so to speak,” says Norbert Wlaka, pointing to the rubber package emerging from the mixer. This package has a temperature of up to 180 degrees Celsius and is now quickly processed into a rubber sheet using an extruder or rollers and prepared for further use in the various elastomer products.
Semperit products are given important properties that determine their quality and durability because the recipe of the rubber mixture has a significant influence on the physical, mechanical, thermal and chemical properties of the end product. By adjusting the mixture, specific attributes such as hardness, elasticity, strength and durability can be optimized. In the case of conveyor belts, this can lead to significantly reduced rolling resistance and thus to energy savings for the customer. For window profiles, on the other hand, it can result in optimized sliding properties or weldable seals.
Strong basis for two divisions
The recipe for the mixture is designed by Semperit’s R&D department, which works closely with the Mixing division. Research and development and the company’s own mixing activities at Semperit’s four locations in Europe and three in Asia thus form the common strong basis for Semperit’s two divisions.
The customized compounds for individual products and customers and the know-how built on 200 years of experience are important reasons for the decision to mix the materials in-house. The high flexibility and speed for new products and price changes for raw materials, independence and a more attractive cost structure are further factors.
“In total, we have around 500 different compounds for our current product range,” says Norbert Wlaka, who has been responsible for Semperit’s Mixing since 2010. Depending on the ingredients, there are different variants of each mixture, known as “compositions”. The entire recipe book for rubber mixtures from the last 200 years can probably be described as an encyclopedia.
“We have around 500 different compounds for our current product range.”
Norbert Wlaka, Head of Mixing
There are four groups of ingredients for rubber compounds: the starting point is the polymer, which can be a synthetic rubber or natural rubber. The added filler, for example carbon black, chalk or silicates, ensures the specific mechanical properties or reduces the mixing costs; plasticizers, such as oils, determine the elasticity and flexibility of the rubber. They are supplemented by additives that are used to improve the properties of the respective product. They can be flame retardants, for example, which increase the safety of the material, antioxidants, which extend the service life, or adhesives, for example in the production of hydraulic hoses, which are supposed to achieve an optimal bond between rubber and steel wire.
The largest mixing plant is located at the Polish site in Bełchatów, where Semperit also operates Europe’s largest production facility for conveyor belts. In Odry, Czech Republic, the site of the largest hose production, Semperit has specialized in hose mixtures. Further mixing plants are located in Wimpassing, Austria, Hückelhoven, Germany, Shanghai, China, Hatyai, Thailand, and Roha, India. “In terms of technology, we are always at the cutting edge. For example, we were among the pioneers in the technical rubber industry in the application of twin screw extruder technology. A plant like this saves the energy of 100 households a year and increases the occupational safety of our employees,” says Norbert Wlaka.
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