The present invention relates to a process for the preparation of a dynamically vulcanized thermoplastic elastomer comprising simultaneously mixing a thermoplastic polyolefin, a vulcanizable rubber and a curing agent in a co-rotating twin-screw extruder whereby the vulcanizable rubber is cured during mixing. The residence time in the extruder is less than 40 sec, the ratio of specific Energy (Espec)/residence time is at least 24 kW/kg and the ratio of the residence time/(Length/Diameter) is less than 0.60 sec. The invention further relates to the dynamically vulcanized thermoplastic elastomer obtainable by the process and to the use of the dynamically vulcanized thermoplastic elastomer in sealing systems, building profiles and extrusion applications.