ES447602A3 - Manufacturing method of machos de fundición. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Method of manufacture of casting cores, characterized in that it comprises: the introduction, in a closed mixing chamber, of sand, liquid binder including a phenol-formaldehyde resin having a benzyl ether bond, at least, per molecule, and a sufficient amount of polyisocyanate as a curing agent for the resin, in addition to a basic catalyst having a pkb within the range of seven to eleven, wherein the resulting mixture has a relatively low reactivity, or even a zero reactivity, for a predetermined range of initial time, during which the said mixture remains in the creep state, followed by a transition to a substantially faster reactivity, during a subsequent time interval, during which said mixture rapidly develops its cohesiveness and hardens; the uniform mixing of said sand, the binder and the catalyst, mixing which is carried out by subjecting said mixture to a vigorous stirring by means of mechanical stirring organs acting on said mixture during a mixing period, previously determined, in response to automatic control organs, connected to said mechanical agitator bodies; the evacuation of said mixture, from said mixing chamber towards a mold or box of cores in response to said automatic control organs; and the control of the amount of said catalyst introduced in said mixture, so that the length of said mixing period, previously determined, and the instant of the evacuation of said mixture inside said mold or box of cores, they are such that the aforementioned evacuation or injection occurs a little before, or at approximately the same time, the aforementioned transition from one reactivity to another occurs. (Machine-translation by Google Translate, not legally binding)