condensed form under pressure or melted if the plastic materials are not soluble fine grinding and suspension in a solvent or reactive agent is helpful average particle sizes of lt 500 u03bcm and especially lt 100 u03bcm have proven useful grinding can also be useful for soluble materials that contain non soluble additives the method in the invention can be used at temperatures from 20 u00b0 c to 200 u00b0 c but especially up to the boiling point of the solvent or agent used if the reaction is carried out under pressure with gaseous agents like nh 3 or lower amines the temperature can also be raised over the boiling point of the amine used the reaction speed depends on the temperature the state of distribution of the material containing polycyanurate and the solvent used wherein with finely distributed materials solution at high temperatures directly in the reactive agent an extremely fast reaction can be achieved within a few hours or less than 1 hour by using appropriate diamines or amino alcohols the method in the invention can be used to obtain di and or polyfunctional amines and or alcohols which can be used as primary materials for the production of polyurethanes melamine resins epoxy resins polyesters polycarbonates etc di and polyfunctional phenols produced can be reconverted into corresponding di and polyfunctional cyanates which can be used as primary materials for new materials containing polycyanurate so that one can speak of real recycling the invention will be described in greater detail using the following examples of embodiment equimolar quantities of a dcba based prepolymer with 50 conversion of cyanate groups and ethyl amine were dissolved in tetrahydrofurane thf into.