POWDER WITH IMPROVED RECYCLING PROPERTIES, PROCESS FOR ITS PRODUCTION AND USE OF THE POWDER IN A PROCESS FOR PRODUCING THREE-DIMENSIONALOBJECTS

摘要

The present invention relates to a powder, to a layer-by-layer process in which regions of the respective pulverulent layer are selectively melted and, after cooling, are fixed, and also to moldings produced from this powder. The RP or RM process produces a body in the shape of a block which is composed firstly of the desired components and secondly, usually predominantly, of unmelted powder, which remains with the components in this block until the molding is revealed, or its covering is removed. The unmelted powder can be used in a further construction process (recycling) after sieving and addition of virgin powder. Unmelted powder of the prior art has a tendency toward post-condensation under the conditions (temperature, and, where appropriate, residual oxygen content) prevailing in the construction chamber of an RP/RM apparatus - and also in particular instances toward uncontrolled cleavage of amino end groups - and the reclaimed powder has markedly increased solution viscosity, and cannot be used, or has only very limited capability for use, in the next construction process. The inventive mixture of oppositely difunctionally regulated polyamide or copolyamide permits preparation of a polyamide powder or copolyamide power with almost constant solution viscosity, capable of use repeatedly in the RP/RM process without addition of virgin powder.