A process for producing an environmentally-friendly plasticizer, which is particularly suitable for use in vehicle tires or technical rubber articles. A vulcanized and/or unvulcanized polymer material of a high molecular weight is converted into a low-molecular phase by direct thermal liquefaction. The vulcanized and/or unvulcanized high-molecular-weight polymer material is provided as a polymer powder and/or a granulated polymer and can be obtained from used tires.
