[0049] Generally, aldehydes of formula R-CHO are used as the aldehydes, wherein R is a hydrogen atom or a carbon atom residue with preferably 1 to 8, particularly preferably 1 to 3 carbon atoms. 

[0050] Examples are formaldehyde, for example in the form of aqueous solutions, or polymers in the form of trioxane or para-formaldehyde, acetaldehyde, propionalde› hyde, furfurylaldehyde (furfural), butyraldehyde, glyoxal and mixtures thereof. Formaldehyde or mixtures containing primarily formaldehyde (relative to the molar amount of the aldehydes) are particularly preferable. 

[0051] Suitable compounds containing nitrogen are for example urea derivatives such as urea itself, melamine or ethylene urea, or amines such as ammonia and triethylam› ine, amino alcohols such as monoethanolamine or 2-amino- 2-methyl-1-propanol. Urea, triethyl amine or monoetha› nolamine, in particular urea, are used in a particularly preferred embodiment. 

[0052] These compounds containing nitrogen can be made to react directly with the furfuryl alcohol or the furfuryl alcohol derivative and the aldehyde compound or with their pre-condensate, or in a preferred variation, added as an independent pre-condensate, in particular in the form of urea derivatives such as preferably urea itself, condensed with an aldehyde, preferably formaldehyde, and optionally con› densed with preferably furfuryl alcohol or a furfuryl alcohol derivative. 

[0053] The amount of nitrogen-containing compounds is selected so that the overall nitrogen content (N) of the resin component determined according to Kjeldahl (according to DIN 16916-02-B2 orVDG memorandum P70), is less than 5% by weight, preferably less than 3.5% by weight and particularly preferably less than 2% by weight so that surface flaws in the cast part resulting from the presence of nitrogen are reduced or avoided. 

[0054] Suitable phenol compounds are characterized by one or more aromatic rings and at least one hydroxy sub› stitution on these rings. In addition to phenol itself, examples are substituted phenols such as cresols or nonyl› phenol, 1,2-dihydroxybenzene (catechol), 1,3-dihydroxy› benzene (resorcinol), cashew nut shell oil, i.e., a mixture consisting of cardanol and cardol, or 1,4-dihydroxybenzene (hydroquinone) or phenolic compounds such as bisphenol A or mixtures thereof. Phenol as a phenolic component is particularly preferable. 

[0055] These phenols can be made to react directly with the furfuryl alcohol and the aldehyde compound or with their pre-condensate. Moreover, reaction products of phe› nols and formaldehyde in the form of resol resins that are produced under alkaline conditions can be added to the resin component. 

[0056] The overall content of free phenol in the resin component is preferably less than 1 % by weight ( determined by gas chromatography). 

[0057] To additionally dilute the above-described resin component to a viscosity range needed for the printing process of 2 mPas to 70 mPas, preferably from 5 mPas to 60 mPas and particularly preferably from 5 mPas to 50 mPas (Brookfield, at 25° C.), the resin component can contain additional solvents such as water or organic solvents that are not furfuryl alcohol comprising 1 to 25 carbon atoms such as alcohols like ethanol, propanol, 5-hydroxy-1,3-dioxane, 4-hydroxymethyl-1,3-dioxolane or tetrahydrofurfuryl alco› hol, oxetanes such as trimethylolpropane oxetane, ketones 

such as acetone or esters such as triacetine and propylene carbonate. Water and ethanol as well as mixtures thereof are particularly preferred. 

[0058] The amount of the solvent(s) added to the resin component is chosen so that the overall water content of the resin component (determined by Karl-Fischer titration according to DIN 51777) is between 5% by weight and less than 40% by weight, preferably 5% by weight and less than 35% by weight, and in particular 7% by weight and less than 30% by weight, and the amount of additional solvents that are not furfuryl alcohol or water is between 0% by weight to 30% by weight, preferably 0.5% by weight to 25% by weight, and in particular 1 % by weight to 20% by weight, relative to the resin component in each case. 

[0059] Moreover, the resin component can contain addi› tional additives such as curing moderators or plastifiers. This includes for example dials or polyols with 2 to 12 carbon atoms, fatty acids, silicones or phthalates that are used in amounts of 0% by weight to 25% by weight, preferably 0% by weight to 20% by weight and particularly preferably in amounts of 0.2 to 15% by weight relative to the resin component. Glycols such as ethylene glycol as well as fatty acids such as oleic acid are particularly preferable. 

[0060] In addition to the components already mentioned, the resin component can contain suitable additives such as surface modifiers which include for example silanes (for example according to EP 1137500 Bl). Suitable silanes are for example amino silanes, epoxy silanes, mercapto silanes, hydroxy silanes and ureido silanes such as gamma-hydroxy› propyl trimethoxysilane, gamma-aminopropyl trimethoxysi› lane, 3-ureidopropyl triethoxysilane, gamma-mercaptopro› pyl trimethoxysilane, gamma-glycidoxypropyl trimethoxysilane, beta-(3,4-epoxy-cyclohexyl)-trimethox› ysilane and N-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane or other polysiloxanes. The added amounts of silanes are in particular between 0% by weight to 5% by weight, preferably between 0.01 % by weight to 2% by weight, and particularly preferably between 0.05% by weight to 1 % by weight, relative to the resin component in each case. 

[0061] As a print medium, the resin component, as described above, has a viscosity (Brookfield, 25° C., spindle 21, DIN EN ISO 2555) of 2 mPas to 70 mPas, preferably 5 mPas to 60 mPas, and particularly preferably from 5 mPas to 50 mPas at 25° C. in each case. Also independent thereof, the surface tension is from 10 mN/m to 70 mN/m, preferably of 15 mN/m to 60 mN/m, particularly preferably from 15 mN/m to 55 mN/m and especially preferably from 20 mN/m to 50 mN/m, determined using the Wilhelmy plate method with a Kriiss Kl00 force tensiometer measured at 20° C. To lower the surface tension, the resin component can be additionally modified with surface-active substances such as cationic, anionic or non-ionic surfactants, such as with carboxylates, sulfonates or sulfates like sodium-2-ethyl› hexyl sulfate as the anionic surfactant, quaternary ammo› nium compounds like esterquats as the cationic surfactants, or alcohols, ethers or ethoxylates likepolyalkylene glycol ether as the nonionic surfactants. 

[0062] It is mentioned in this context that the printing temperature, i.e., the temperature of the printhead, is not restricted to room temperature but can instead lie between 20° C. to 80° C., in particular 20 to 40° C., and even higher viscosity binders can thereby be easily printed. 

