Abstract:
Process for producing a syntactically foamed polymer composition, comprising a) introducing expandable microspheres into a matrix material and mixing in a mixing machine, b) expanding the microspheres, c) the temperature distribution in the mixing machine being inhomogeneous in a plane perpendicular to the transport direction of the machine, d) maintaining the temperature of a first surface bounding the mixing space of the mixing machine, in a plane perpendicular to the transport direction of the mixing machine, at a temperature sufficient for the polymer composition containing the microspheres coming into contact with such first bounding surface to reach a temperature sufficient for commencement and continuation of expansion, e) maintaining a second surface bonding the mixing space in the same plane at a temperature sufficiently low for the polymer composition containing the microspheres coming into contact with it, not to reach a temperature sufficient for commencement and continuation of expansion.