The invention relates to
thermoplastic cross-linked
polymer compound with thermally reversible urethane crosslinkages comprising the following essential components a) to d): a) a
thermoplastic polymer component with saturated molecular main chain: b) a component containing
isocyanate group(s), either attached to the
polymer chain or being present in mobile form in the polymer matrix; c) a component containing hydroxyl group(s) either attached to the polymer chain or being present in mobile form in the polymer matrix; d) a catalyst
package promoting the reversible formation and
thermal dissociation of urethane bonds, characterized in that at least one of the components b) and c) is attached to the polymer chain and at least one of the additives present in the compound is multi-functional, playing a role in more than one,
functionally independent processes. The invention further relates to a process for preparing such compounds by: a) preparing a first additive
package containing the
monomer(s) of one of the components b) and c) to be grafted and the radical source and a
processing aid, by mixing the
processing aid first with the radical source, then with other component(s), b) preparing a second additive
package containing the other urethane forming component not present in the first additive package, the
processing aid, the urethane catalysts and, if both the hydroxyl and the
isocyanate components are to be grafted, the radical source, such as
peroxide, by mixing first the
processing aid with the
solid components, then with other component(s), c) melting the
thermoplastic polymer, d) mixing the first additive package with the molten polymer at a temperature where the
grafting reaction is complete within a few minutes, e) mixing the second additive package with the molten polymer obtained in step, d) at a temperature where the urethane formation reaction is complete within a few minutes, f) followed by proper shaping (e.g.
extrusion /
granulation, injection, etc.) the compound and
cooling down.