# METHOD FOR PRODUCING THREE-DIMENSIONALLY LAYERED SHAPED BODIES 

[0001] The invention relates to a method for producing three-dimensionally layered shaped bodies by means of layer-by-layer construction using a resin component which contains at least one furane resin, and more than 5% by weight and less than 50% by weight monomer furfuryl alcohol, and an acid. The shaped bodies produced in this manner are suitable inter alia as casting molds and casting cores for metal casting. 

[0002] Various methods are known for the layer-by-layer construction of three-dimensionally shaped bodies. With the assistance of these methods, bodies with even the most complicated geometries can be produced directly layer-by› layer by 3D printing from the CAD data without molding tools. This is not possible with conventional methods requir› ing molds. 

[0003] WO 2001/068336 A2 discloses various binders for layer-by-layer construction. Inter alia, the use of a furane resin (not described further) with at least 50% furfuryl alcohol and at most 4% ethylene glycol is also cited as binder components. The resin component of the binder is sprayed layer-by-layer over the entire working surface of the loose basic mold material and then is also cured layer-by› layer, but with the selective application of a hardener such as an organic acid. 

[0004] EP 1268165 Bl varies this method in that both the liquid binder, inter alia also a furane resin that is not described further as well as a liquid hardener are applied selectively and layer-by-layer sequentially in the sequence of resin component and then hardener to the sections to be cured. 

[0005] According to EP 1509382 Bl, the resin component of the binder is not applied layer-by-layer by means of a printhead, but rather is mixed directly with the basic mold material and applied layer-by-layer together with the basic mold material. This mixture consisting of the resin compo› nent and basic mold material is then cured by the selective application of the hardener. 

[0006] In EP 1638758 Bl, the sequence of addition is reversed. First, the basic mold material is premixed with a hardener, and then the resin component is selectively applied layer-by-layer. Inter alia, acids such as aqueous para-tolu› enesulfonic acid are described as the hardener and once more inter alia furane resins are described as the resin component, although again, if further specified, using a furane resin with at least 50% furfuryl alcohol. 

[0007] A method is described in DE 102014106178 Al in which a basic mold material is hardened in layers by means of an alkaline phenol resin, an ester, and optionally an inorganic additive. 

[0008] In particular, the system of acid/furane resin cor› responding to EP 1638758 Bl and the system of ester/ alkaline phenol resin corresponding to DE 102014106178 Al have been accepted somewhat in practice in the layer› by-layer construction of molded bodies and are used in the development of new cast parts and in the production of individual parts or small series when conventional produc› tion with molding tools would be too complicated and expensive, or respectively only describable with a compli› cated core package. 

[0009] In particular, the acid/furane resin system has the disadvantage that shaped bodies produced according to this 

method must first be freed in an involved manner from an adhering and non-printed mixture consisting of the basic mold material and acid or resin component. Individuals who perform this task are exposed to dusts and solvent and binder vapors. 

[0010] The object of the present invention is to provide a binder for the layer-by-layer construction of three-dimen› sional shaped bodies that permits the layer-by-layer produc› tion of three-dimensional shaped bodies that can be freed easily and with a sharp contour from a non-printed, adhering mixture consisting of the basic mold material and the acid or resin component. Beyond the significant time savings, the reduced exposure to solvent and binder vapors is an addi› tional advantage in this case. 

[0011] It was surprisingly found that a binder comprising at least: 

[0012] (a) a resin component containing at least one furane resin obtainable by reacting at least one alde› hyde compound, in particular formaldehyde, with fur› furyl alcohol, and possibly with additional monomers, as well as more than 5% by weight, preferably more than 10% by weight, and particularly preferably more than 15% by weight, as well as less than 50% by weight, preferably less than 45% by weight and par› ticularly preferably less than 40% by weight monomer furfuryl alcohol relative to the resin component, and 

[0013] (b) an acid 

significantly reduces the problem of adhesions by a non› printed mixture consisting of acid and the basic mold material, or the resin component and basic mold material, to the shaped bodies produced in this manner. 

[0014] These and other objects are achieved by the subject of the independent claims; advantageous developments are the subject of the dependent claims or are described below. 

[0015] The present invention therefore comprises a binder comprising an acid and a resin component comprising at least one furane resin, and containing monomer furfuryl alcohol of, on the one hand, more than 5% by weight, preferably more than 10% by weight, and particularly pref› erably more than 15% by weight furfuryl alcohol, and on the other hand less than 50% by weight, preferably less than 45% by weight, and particularly preferably less than 40% by weight monomer furfuryl alcohol relative in each case to the resin component. 

[0016] The furane resin is characterized in that it is constructed from aldehyde compound(s ), in particular form› aldehyde, with furfuryl alcohol and possibly with additional monomers such as in particular urea, furfuryl alcohol deriva› tives (by definition, the furfuryl alcohol derivatives therefore do not comprise furfuryl alcohol itself) and/or phenol derivatives. In this case, the furane resin is constructed in particular of furfuryl alcohol and formaldehyde as mono› mers by more than 60% by weight, preferably more than 70% by weight, and particularly preferably more than 80% by weight overall relative to all of the monomers used. With this binder, the so-called job box of the 3-D printer can be used spatially with greater efficiency, i.e., shaped bodies can be produced closer to each other in space since a "fusion" of the shaped bodies is prevented given the reduced tendency 

## Object of the Invention 

## SUMMARY OF THE INVENTION 

