Method for producing thermally crosslinkable polymers in a planetary roller extruder, wherein a) the planetary roller extruder possesses a feed section and a compounding section, the latter being formed by a roller cylinder area that consists of at least two coupled roller cylinders (2,3), whose planetary spindles are driven by a single common central spindle, wherein b) the polymers are supplied in a plastified state to the planetary roller extruder, wherein c)the plastified polymers are fed into the first roller cylinder, namely within the first half of the first roller cylinder, wherein d) the feed section of the planetary roller extruder is subjected to a vacuum, characterised in that e) in the case where the roller cylinder area is formed by two roller cylinders (2,3), the casing of the second roller cylinder possesses an opening, through which air and possibly other volatile components are removed from the plastified polymers by means of a vacuum, or in another case, where the roller cylinder area is formed by more than two roller cylinders, the casing of the second roller cylinder of the at least three roller cylinders (2,3,4), or the casing of a subsequent downstream roller cylinder possesses an opening, through which air and other volatile components are removed from the plastified polymers by means of a vacuum, f) wherein the temperatures of the central spindle and of the two roller cylinders (2,3) under vacuum are preset, such that the polymers to be degassed remain in a plastic state, g) wherein downstream of the vacuum degassing point, one or more liquids such as thermal crosslinkers, crosslinking accelerators, colourant solutions or colourant dispersions are dosed into the plastified polymers, thus to the second roller cylinder or to one or more of the additional roller cylinders or to an intermediate ring between the second and third roller cylinders or between the third and fourth roller cylinder, h) wherein the blends of plastified polymers and liquids in the roller cylinder area, in which the liquids are incorporated into the plastified polymers, are cooled down such that, after exiting the planetary roller extruder, no evaporation takes place of the liquids that have been preferably homogeneously blended into the plastified polymers, i) wherein the length of the roller cylinder area, in which the plastified polymers are degassed under vacuum, is between 50 % and 80 % of the length of the entire roller cylinder area, j) wherein the blend of plastified polymers and modifying liquids is fed into a coating unit. a) the planetary roller extruder possesses a feed section and a compounding section, the latter being formed by a roller cylinder area that consists of at least two coupled roller cylinders (2,3), whose planetary spindles are driven by a single common central spindle, wherein b) the polymers are supplied in a plastified state to the planetary roller extruder, wherein c)the plastified polymers are fed into the first roller cylinder, namely within the first half of the first roller cylinder, wherein d) the feed section of the planetary roller extruder is subjected to a vacuum, characterised in that e) in the case where the roller cylinder area is formed by two roller cylinders (2,3), the casing of the second roller cylinder possesses an opening, through which air and possibly other volatile components are removed from the plastified polymers by means of a vacuum, or in another case, where the roller cylinder area is formed by more than two roller cylinders, the casing of the second roller cylinder of the at least three roller cylinders (2,3,4), or the casing of a subsequent downstream roller cylinder possesses an opening, through which air and other volatile components are removed from the plastified polymers by means of a vacuum, f) wherein the temperatures of the central spindle and of the two roller cylinders (2,3) under vacuum are preset, such that the polymers to be degassed remain in a plastic state, g) wherein downstream of the vacuum degassing point, one or more liquids such as thermal crosslinkers, crosslinking accelerators, colourant solutions or colourant dispersions are dosed into the plastified polymers, thus to the second roller cylinder or to one or more of the additional roller cylinders or to an intermediate ring between the second and third roller cylinders or between the third and fourth roller cylinder, h) wherein the blends of plastified polymers and liquids in the roller cylinder area, in which the liquids are incorporated into the plastified polymers, are cooled down such that, after exiting the planetary roller extruder, no evaporation takes place of the liquids that have been preferably homogeneously blended into the plastified polymers, i) wherein the length of the roller cylinder area, in which the plastified polymers are degassed under vacuum, is between 50 % and 80 % of the length of the entire roller cylinder area, j) wherein the blend of plastified polymers and modifying liquids is fed into a coating unit.