FORMALDEHYDE-REDUCED PHENOL RESIN BINDER

Description

[0001] The present invention relates to formaldehyde-reduced phenolic resins of the benzyl ether type, containing at least one formaldehyde scavenger in the form of a beta-dicarbonyl compound and furthermore an alpha-carbonyl carboxyl compound, in particular glyoxylic acid, binders based on these phenolic resins, and isocyanate compounds with at least two isocyanate groups for use in phenolic resin-polyurethane cold box (PUCB) processes and / or phenolic resin-polyurethane no-bake (PUNB) processes. The invention further relates to molding compound mixtures containing the binder and a process for producing cores, molds, or risers. In particular, but not necessarily, the polyol component for producing the molding compound mixture already contains the beta-dicarbonyl compound and compounds with an alpha-carbonyl carboxyl structure. Background of the invention and general state of the art

[0002] The production of cores and molds using the PUCB and / or PUNB processes has become highly significant in the foundry industry. Two-component polyurethane systems are used to bind a refractory mold base material. The polyol component consists of a polyol with at least two OH groups per molecule, and the isocyanate component consists of an isocyanate with at least two NCO groups per molecule. Phenol-formaldehyde resins are among the materials used as the polyol component. In the PUCB process, the curing of the mixture of mold base material and binder, also referred to as the molding compound mixture, is achieved using low-boiling tertiary amines, which are passed through the molding compound mixture in gaseous or aerosol form after shaping (see US 3409579). This is typically done using a carrier gas, such as air, nitrogen, or CO₂, into which at least one tertiary amine is introduced.In the PUNB process, liquid tertiary amines and / or metal compounds are added as a catalyst to the molding material mixture.

[0003] There has been no shortage of attempts to reduce the formaldehyde content of such phenol-formaldehyde resins, such as resoles or phenolic resins, in particular phenol-formaldehyde resins of the benzyl ether type, to levels of free formaldehyde of less than 0.1 wt.%, in particular less than 0.01 wt.%.

[0004] US 5358748 proposes the use of formaldehyde scavengers for aqueous acidic resols. Heterocyclic nitrogen compounds treated with acids (preferably sulfamic acid) are used as formaldehyde scavengers.

[0005] US patent 5795933 also discloses the use of formaldehyde scavengers in phenol-formaldehyde resins to reduce the free formaldehyde content. Beta-dicarbonyl compounds such as 1,3-cyclohexanedione, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate, or methyl tert-butyl malonate are used as formaldehyde scavengers. Volatile solvents may be included as additives.

[0006] US patent 2011 / 0015341 A1 discloses the production of phenol-formaldehyde resins in the presence of formaldehyde scavengers. Beta-dicarbonyl compounds are used as formaldehyde scavengers. The phenol-formaldehyde resins are produced by alkali-catalyzed condensation.

[0007] WO 2016 / 165916 A1 describes a phenolic resin composition for use in polyurethane cold-box and / or no-bake processes. The phenolic resin composition comprises an orthocondensed phenolic resol with etherified and / or free methylol groups in a total amount of 40 to 60 wt% and free formaldehyde in an amount of less than 0.1 wt%, each based on the total mass of the phenolic resin composition, and one or more reaction products of formaldehyde with one or more CH-acidic compounds. Beta-dicarbonyl compounds for the reduction of free formaldehyde are disclosed as CH-acidic compounds. Dimethyl malonates and diethyl malonates are preferably used. The reaction products when using a malonic acid ester as a CH-acidic starting compound include in particular 2-methylene malon ester, 2,2-bis(hydroxymethyl) malon ester, 2-(hydroxymethyl) malon ester and 2-(3-hydroxy-2-oxa-propyl) malon ester.The proportion of free formaldehyde is specified as less than 0.1 wt.%, preferably less than 0.08 wt.%, and particularly preferably less than 0.05 wt.%, in each case based on the phenolic resin composition. A lower limit for free formaldehyde is not specified. Preferably, the orthocondensed phenolic resol is a benzyl ether resin of the following formula (where m / n is greater than or equal to 1): .

[0008] No details are given regarding the strength of the resulting cured molding materials. An alpha carbonyl carboxyl compound is not used. While the addition of beta-dicarbonyl compounds such as ethyl acetoacetate reduces the free formaldehyde content, unfortunately, as demonstrated here, the strength also decreases. The present invention aims to counteract this. Object of the invention

[0009] The object of the invention is to provide binders based on benzyl ether-type phenolic resins for use in the phenolic resin-polyurethane cold box process (PUCB process) and / or in the phenolic resin-polyurethane no-bake process (PUNB process), wherein the phenolic resin composition containing the benzyl ether-type phenolic resins, used as a component of the binder, has a very low free formaldehyde content and the binder is intended to lead to high strengths. Summary of the invention

[0010] The above and further problems will be solved by the subject matter of the independent patent claims. Advantageous further developments are the subject matter of the dependent claims or described below.

[0011] The invention relates to a binder containing phenolic resins of the benzyl ether type (preferably contained in the polyol component) which, after the use of the formaldehyde scavenger in the form of a beta-dicarbonyl compound and the alpha-carbonyl carboxyl compound, has a free formaldehyde content relative to the phenolic resin composition of preferably less than 0.01 wt.%.

[0012] Surprisingly, it was found that the free formaldehyde content in phenolic resin compositions as a starting component of such binders cannot be reduced arbitrarily without accepting disadvantages in the strengths of the cores and molds produced from them.

[0013] Depending on the phenolic resin composition used, which may contain solvents and / or additives in addition to the benzyl ether resin, such low levels of free formaldehyde in the phenolic resin composition lead to a reduction in the strength of the resulting cured binder or molding compound. This is unacceptable. Surprisingly, it has now been found that the strength can be restored (almost) to the level of a phenolic resin composition with a higher free formaldehyde content by adding a compound with an alpha-carbonyl carboxyl structure.

[0014] The phenolic resin composition according to the invention thus contains: Phenolic resins of the benzyl ether type; at least one or more formaldehyde-reducing compound(s) with a beta-dicarbonyl structure (having at least two carbonyl groups in the 1,3 position, one of which is a carbonyl group (-C=O) and the other a carboxyl group (-C(=O)(-O-)), or their reaction products with formaldehyde; at least one or more compound(s) with an alpha-carbonyl-carboxyl structure (having at least one carbonyl group in the 2 position to the carboxyl group), preferably glyoxylic acid and its derivatives or their reaction products, wherein the free formaldehyde content in the phenolic resin composition is in particular less than 0.05 wt.%, preferably from 0.0490 wt.% to 0.0050 wt.%, particularly preferably from 0.0099 wt.% to 0.0025 wt.% and particularly preferably from 0.0090 wt.% to 0.0010 wt.%.

[0015] The invention further relates to molding material mixtures containing a binder based on benzyl ether-type phenolic resins, refractory molding base material, and isocyanates, and optionally catalysts, as well as cores, molds, and risers produced from the molding material mixtures after hardening. The invention also relates to the use of the cores, molds, and risers for metal casting, in particular iron and aluminum casting. Detailed description of the invention

[0016] All conventionally used phenolic compounds are suitable for the production of benzyl ether-type phenolic resins. In addition to unsubstituted phenols, substituted phenols or mixtures thereof can be used. The phenolic compounds are preferably either unsubstituted at both ortho positions or unsubstituted at one ortho and one para position. The remaining ring carbon atoms may be substituted. The choice of substituent is not particularly restricted, provided the substituent does not adversely affect the reaction of the phenol with the aldehyde. Examples of substituted phenols are alkyl-substituted, alkoxy-substituted, aryl-substituted, and aryloxy-substituted phenols.

[0017] The basic structure of a benzyl ether-type phenolic resin has, in addition to -CH2- linked phenol units, -CH2-O-CH2- linked phenol units and can be represented by example (with reference to a product reacted only with formaldehyde) as follows:

[0018] The different units are typically statistically distributed (i.e., linked in a different order than shown above). The phenol unit may also be para-linked. In this case, R and R' are each independent (especially of m and n) of hydrogen or a C1 to C26 hydrocarbon substituent (saturated or unsaturated, straight-chain or branched) in the ortho, meta, or para position to the phenolic hydroxy group; the sum of m and n is at least 2 and the m / n ratio is at least 1; R is independent of hydrogen, -CH₂OH, or -CH₂OR" with R" being a C1 to C9 hydrocarbon. The residue R" can be straight-chain or branched, saturated or unsaturated.

[0019] The aforementioned substituents have, for example, 1 to 26, preferably 1 to 15 carbon atoms. Examples of suitable phenols are o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 3,4,5-trimethylphenol, 3-ethylphenol, 3,5-diethylphenol, p-butylphenol, 3,5-dibutylphenol, p-amylphenol, cyclohexylphenol, p-octylphenol, p-nonylphenol, cardanol, 3,5-dicyclohexylphenol, p-crotylphenol, p-phenylphenol, 3,5-dimethoxyphenol, and p-phenoxyphenol.

[0020] Phenol itself is particularly preferred; higher condensed phenols, such as bisphenol A, are also suitable. Furthermore, polyhydric phenols, which possess more than one phenolic hydroxyl group, are also suitable.

[0021] Preferred polyhydric phenols possess 2 to 4 phenolic hydroxyl groups. Specific examples of suitable polyhydric phenols are catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, 2,5-dimethylresorcinol, 4,5-dimethylresorcinol, 5-methylresorcinol, cardol, or 5-ethylresorcinol. Mixtures of various mono- and polyhydric and / or substituted and / or condensed phenolic components can also be used for the preparation of the polyol component.

[0022] In one embodiment, phenols of general formula I: used for the preparation of the phenolic resin component, wherein A, B and C are independently selected from: a hydrogen atom, a branched or unbranched alkyl or alkenyl group with up to 3 double bonds, which may, for example, have 1 to 26, preferably 1 to 15 carbon atoms, a branched or unbranched alkoxy group, which may, for example, have 1 to 26, preferably 1 to 15 carbon atoms, a branched or unbranched alkenoxy group, which may, for example, have 1 to 26, preferably 1 to 15 carbon atoms, an aryl or alkylaryl group, such as bisphenyls.

[0023] In addition to formaldehyde, aldehydes of the formula R-CHO are also suitable for the production of benzyl ether-type phenolic resins, where R is a carbon residue with 1 to 3 carbon atoms, preferably one carbon atom. Acetaldehyde and propionaldehyde are specific examples. Formaldehyde is particularly preferred, either in its aqueous form, as para-formaldehyde, or as trioxane.

[0024] To obtain benzyl ether-type phenolic resins, at least an equivalent number of moles of aldehyde compound is preferably used, based on the number of moles of phenol compounds. Preferably, the molar ratio of aldehyde compound to phenol compound is 1.05 : 1.0 to 2.5 : 1, particularly preferably 1.1 : 1 to 2.2 : 1, and especially preferably 1.2 : 1 to 2.0 : 1.

[0025] According to EP 0177871 A2, aliphatic monoalcohols with one to eight carbon atoms, particularly those with one or two carbon atoms, can be added as further reaction components. The alkoxylation is intended to give the phenol-formaldehyde resins increased thermal stability and a longer sand lifespan.

[0026] The benzyl ether-type phenol resin is produced according to methods known to those skilled in the art. The phenol and the aldehyde are reacted in the presence of a divalent metal ion at temperatures preferably below 130°C. The resulting water is distilled off. A suitable energizing agent, such as toluene or xylene, can be added to the reaction mixture, or the distillation can be carried out at reduced pressure.

[0027] Suitable catalysts for the production of benzyl ether-type phenolic resins are salts of divalent ions of metals such as Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca, and Ba, particularly Zn salts. Zinc acetate is preferred. The amount used is not critical. Typical amounts of metal catalyst are 0.02 to 0.3 wt.%, preferably 0.02 to 0.18 wt.%, based on the total amount of phenol compound and aldehyde compound.

[0028] Such resins are described, for example, in US 3485797 and in EP 1137500 B1, to whose disclosures reference is hereby expressly made both with regard to the benzyl ether-type phenolic resins themselves and with regard to their manufacture.

[0029] The free phenol content, based on the weight of the benzyl ether-type phenol resin, is preferably less than 12 wt.%, particularly preferably less than 10 wt.% or even less than 2 wt.%.

[0030] According to a further embodiment, the phenolic resin composition can contain free saligenin; preferably, the weight ratio of free phenol to free saligenin is from 1:1.1 to 1:12, particularly preferably from 1:1.5 to 1:10, and especially from 1:1.8 to 1:8. "Free" in this sense means "unbound" in the composition.

[0031] The formaldehyde scavengers used according to the invention are CH-acidic compounds in the form of beta-dicarbonyl compounds (1,3-dicarbonyl compounds) (I) comprising one or more of the following group(s): R 1< C(=O)-CH 2 -C(=O)-O- (I) wherein R1 is H, a C1 to C12 hydrocarbon, preferably a C1 to C7 hydrocarbon, or -CH2-X, where X is a residue containing, besides hydrogen atoms, 1 to 11 carbon atoms, preferably 1 to 6 carbon atoms, and 1 to 3 oxygen atoms; for example, oxygen may be present in the form of ether groups. R1 should not be bonded to the carbonyl carbon atom by an oxygen atom. Examples of R1 are H, alkyl, alkenyl, aryl, alkylaryl, or alkenylaryl.

[0032] In particular, the beta-dicarbonyl compounds have the following structure: up, in which R1< has the meaning described above, and R2< is H, a C1 to C14 hydrocarbon, preferably a C1 to C7 hydrocarbon, optionally containing 1 to 3 oxygen atoms, for example in the form of ether groups. Examples of R2< are alkyl, alkenyl, aryl, alkoxy, alkenyloxy, or aryloxy.

[0033] When the CH-acidic CH₂ group reacts with formaldehyde, the CH₂ group is transformed, for example, into a C(-H)(-CH₂-OH) or -C(-CH₂-OH)₂ group. Further reaction products are listed in WO 2016 / 165916 A1 on pages 15 and 16.

[0034] It is also possible that the beta-dicarbonyl compound is a compound that has several beta dicarbonyl groups (I), e.g. 2 to 4, especially those according to formula (II), which are linked via R 2< and thus have several CH acidic groups in the molecule (compare e.g. CAS: 22208-25-9).

[0035] CH acidity is the tendency of a compound to donate the hydrogen atoms bonded to a carbon atom as protons, thus formally acting as an acid. Unsubstituted alkanes exhibit high pKa values ​​(e.g., approximately 50 for ethane). However, if the carbon atom is bonded α-in the position to strongly electron-withdrawing groups such as carbonyls (in an ester, ketone, or aldehyde), the pronounced negative inductive effect causes the CH bond at the α-carbon atom to become more polarized, making the proton more readily available. According to the present invention, the pKa value of the CH-acidic CH₂ group is preferably less than 15, and particularly between 5 and 12.

[0036] Malonic acid esters, such as diethyl malonate or dimethyl malonate, are less suitable. Beta-keto esters are preferred. Examples of beta-keto esters include: Methylacetoacetat (Acetessigsäuremethylester, Butan-3-onsäuremethylester CAS: 105-45-2), Ethylacetoacetat (Ethyl-3-oxobutyrat, 3-Oxobutansäureethylester, CAS: 141-97-9) Isopropylacetoacetat (Isopropyl-3-oxobutanoat, CAS: 542-08-5) Isobutylacetoacetat (CAS: 7779-75-1) t-Butylacetoacetat (CAS: 1694-31-1), Benzylacetoacetat (CAS: 5396-89-4), Dodecylacetoacetat (CAS: 52406-22-1), Ethylbenzoylacetat (CAS: 94-02-0), 2-Methoxyethylacetoacetat (CAS: 22502-03-0), 2-Acetoacetoxyethylmethacrylat (CAS: 21282-97-3), Methyl-4-methyl-3-oxopentanoat (CAS: 42558-54-3) und Trimethylolpropantrisacetoacetat (CAS: 22208-25-9):

[0037] Particularly preferred are methylacetoacetate, ethylacetoacetate, benzylacetoacetate, dodecylacetoacetate, ethylbenzoyl acetate, 2-methoxyethylacetoacetate, 2-(acetoacetoxy)ethyl methacrylate, and trimethylolpropanitrisacetoacetate. Methylacetoacetate, ethylacetoacetate, and trimethylolpropanitrisacetoacetate are especially preferred.

[0038] Nitrogen-containing beta-dicarbonyl compounds (II) are also suitable as formaldehyde scavengers. Beta-dicarbonyl compounds (I) can also be used. Examples include: N-Methylacetoacetamide (CAS: 20306-75-6) N,N-Dimethylacetoacetamide (CAS: 2044-64-6) and N,N-diethylacetoacetamide (CAS:2235-46-3).

[0039] Further formaldehyde scavengers (III) that can be used according to the invention contain nitrogen in the molecule. Urea, and in particular ethylene urea and / or propylene urea, are preferably used. These can be used in addition to the beta-dicarbonyl compounds (I).

[0040] Combinations of the aforementioned formaldehyde scavenger classes (I to III) within a class and / or among themselves are possible, as long as at least one beta-dicarbonyl compound (I) is used.

[0041] Preferably, the benzyl ether-type phenolic resin already has a low free formaldehyde content before the addition of the formaldehyde scavenger. This can be controlled, among other things, by the process parameters, which means that less formaldehyde scavenger needs to be used to reliably achieve the limit of <0.01 wt.% in the phenolic resin composition.

[0042] The limit of 0.01% by weight is significant because below this limit, the phenolic resin formulation is no longer considered to have sensitizing properties (caused by free formaldehyde). Therefore, from an occupational safety perspective, it is desirable to reduce the free formaldehyde content as much as technically possible.

[0043] The preferred content of free formaldehyde in the phenolic resin composition, or even just the benzyl ether-type phenolic resin, before the addition of the formaldehyde scavenger, is less than 0.25 wt.%, preferably 0.18 to less than 0.25 wt.%, and particularly preferably 0.10 to 0.20 wt.%, in each case based (only) on the benzyl ether-type phenolic resin.

[0044] The water content of the benzyl ether resin can be controlled through process control. A content of 0.2 to 0.9 wt.% is preferred, more preferably 0.3 to 0.9 wt.%, and most preferably 0.4 to 0.9 wt.%.

[0045] The benzyl ether-type phenol resin is produced according to a process known to those skilled in the art. In this process, phenol and aldehyde are reacted in the presence of a divalent metal ion at temperatures preferably below 130°C. The resulting water is distilled off. A suitable energizing agent, such as toluene or xylene, can be added to the reaction mixture, or the distillation can be carried out at reduced pressure. The concentration of phenol can be altered (in particular minimized) by means of the energizing agent or steam distillation, and thus the ratio of phenol to saligenin can also be changed.

[0046] Titrimetric methods cannot be used to determine free formaldehyde at the low concentrations required by the invention. Here, an HPLC method is performed: derivatization of the formaldehyde with acetylacetonate and ammonium acetate buffer. Detector: UV-VIS 413 nm Column temperature: 50°C Flow rate: 1.5 µl / min Sample volume: 15 µl Column: RP column MZ-Analytical Spherisorb ODS-2, C 18 3 µm, Macherey-Nagel Low-pressure gradient: Water / acetonitrile in different weight parts

[0047] The amount of formaldehyde scavenger in relation to the beta-dicarbonyl compounds (I) is not critical and can be, for example, up to 1.5 wt.%, preferably 0.1 to 1.0 wt.% and particularly preferably 0.15 to 0.9 wt.% based on this phenolic resin composition.

[0048] Furthermore, an alpha-carbonyl-carboxyl compound is used. This contains at least one carbonyl group (C=O) in the alpha position (i.e., the 2 position relative to the carboxyl group) to at least one carboxyl group (-C(=O)-O-) and thus has the following structure: R 3< -(C=O)-C(=O)-OR 4< (III) where R 3< and R 4< each independently represent H or a C1- to C6-, in particular C1- to C4- hydrocarbon, e.g. alkyl or alkenyl, preferably H, CH 3 or C 2 H 5. It is particularly preferred that at least one R of R 3< and R 4< is equal to H, preferably both.

[0049] The alkyl group can be linear or branched. Particularly suitable are: Glyoxylic acid (CAS: 298-12-4), Glyoxyacid ethyl ester (CAS: 924-44-7) 2-Ketobutanoic acid (CAS: 600-18-0) 2-Ketobutanoic acid methyl ester (CAS: 3952-66-7)

[0050] Glyoxylic acid or ketobutanoic acid, particularly glyoxylic acid, is preferably used. Several alpha-carbonyl carboxyl compounds can also be mixed together.

[0051] The amount of alpha-carbonyl carboxyl compound is not critical and can be, for example, 0.01 to 1.0 wt.%, preferably 0.02 to 0.5 wt.% and particularly preferably 0.04 to 0.0999 wt.%, based on the phenolic resin composition.

[0052] What is particularly surprising is that the addition of another acidic component, such as glyoxylic acid, to the phenolic resin composition does not reduce the stability of the polyol component, and in particular the free formaldehyde level remains stably low over time.

[0053] The isocyanate component of the binder system comprises an aliphatic, cycloaliphatic, or aromatic monomeric or polymeric isocyanate, preferably with an average of 2 to 5 isocyanate groups per molecule. Depending on the desired properties, mixtures of isocyanates can also be used.

[0054] Suitable isocyanates include aliphatic isocyanates, such as hexamethylene diisocyanate, alicyclic isocyanates such as 4,4'-dicyclohexylmethane diisocyanate, and dimethyl derivatives thereof. Examples of suitable aromatic isocyanates are toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate, and methyl derivatives thereof, as well as polymethylene polyphenyl isocyanates. Preferred isocyanates are aromatic isocyanates; polymethylene polyphenyl polyisocyanates, such as technical-grade 4,4'-diphenylmethane diisocyanate (i.e., 4,4'-diphenylmethane diisocyanate with a proportion of isomers and higher homologs), are particularly preferred.

[0055] Polyisocyanates can also be derivatized by reacting divalent isocyanates with each other in such a way that some of their isocyanate groups are derivatized to isocyanurate, biuret, allophanate, uretdione, or carbodiimide groups. Dimerization products containing uretdione groups, such as those of MDI or TDI, are of particular interest. However, such derivatized polyisocyanates are preferably used only as a component alongside the non-derivatized polyisocyanates mentioned above.

[0056] Preferably, the isocyanate is used in an amount such that the number of isocyanate groups is 80 to 120%, based on the number of free hydroxyl groups of the resin.

[0057] The phenolic resin component or the isocyanate component of the binder system is preferably used as a solution in an organic solvent or a combination of organic solvents. Solvents may be necessary, for example, to maintain the binder components in a sufficiently low viscosity state. This is required, among other things, to ensure uniform cross-linking of the refractory molding material and its free-flowing properties.

[0058] In addition to aromatic solvents known, for example, as solvent naphtha, other solvents can be used for the phenolic resin composition. Starting with benzene, alkyl and / or alkenyl groups are independently substituted on the aromatic ring, having a chain length of C1 to C30, preferably C1 to C20, and particularly preferably C1 to C16. One to six ring hydrogens of the benzene can be independently substituted for an alkyl and / or alkenyl group; preferably 1 to 4, and particularly preferably 1 to 3 ring hydrogens are substituted. The alkyl or alkenyl chain can be straight or branched.

[0059] Oxygen-rich polar organic solvents can also be used. Particularly suitable are dicarboxylic acid esters, glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters (lactones), cyclic carbonates, or silicic acid esters, or mixtures thereof. Dicarboxylic acid esters, cyclic ketones, and cyclic carbonates are preferred.

[0060] Typical dicarboxylic acid esters have the formula RI< OOC-R II< -COOR III<, where R II< and R III< each independently represent an alkyl group with 1 to 12, preferably 1 to 6, carbon atoms, and R II< is a hydrocarbon group, straight-chain or branched, with 1 to 7 carbon atoms. Examples include dimethyl esters of carboxylic acids with 4 to 6 carbon atoms, which are available, for example, under the name Dibasic Ester from DuPont.

[0061] Typical glycol ether esters are compounds of the formula R IV< -OR V< -OOCR VI< , where R IV< represents an alkyl group with 1 to 4 carbon atoms, RV< is a hydrocarbon group with 2 to 4 carbon atoms and R VI< is an alkyl group with 1 to 3 carbon atoms, e.g. butyl glycol acetate, glycol ether acetates are preferred.

[0062] Typical glycol diesters have the general formula R<IV>COO-R<V<-OOCR<VI<, where R<IV< to R<VI< are defined as above and the residues are selected independently of each other (e.g., propylene glycol diacetate). Glycol diacetates are preferred. Glycol diethers can be characterized by the formula R<IV<-O-RV<-OR<VI<, where R3 to R5 are defined as above and the residues are selected independently of each other (e.g., dipropylene glycol dimethyl ether).

[0063] Typical cyclic ketones, cyclic esters, and cyclic carbonates with 4 to 5 carbon atoms are also suitable (e.g., propylene carbonate). The carbon atoms can be branched or unbranched and can be saturated or unsaturated.

[0064] Also suitable are fatty acid esters R VII< -OOCR VIII< with R VIII< a hydrocarbon from C8 to 32, and R VII< a hydrocarbon from C1 to C9, especially C1 to C4, such as rapeseed oil fatty acid methyl ester, oleic acid butyl ester and isopropyl esters of various fatty acids.

[0065] Silica esters, in their monomeric form or as oligomers, as known from WO 2009 / 130335 A2, are also suitable. Suitable alkyl / alkoxy silanes or alkyl / alkoxy siloxanes are, for example, esters of orthosilicic acid in which 1, 2, or 3 alcohol groups are replaced by substituted or unsubstituted hydrocarbon groups, compounds of the formula RIX<nSi(ORX4)n, where n = 1, 2, or 3, each group RXn, regardless of any further groups RXnnn, denotes an organic group, preferably branched or unbranched C1- to C30-alkyl or aryl, as defined accordingly in connection with the first aspect. R IX< is a substituted or unsubstituted, branched or unbranched hydrocarbon residue, and the residues R IX< are the same or different in the case of n = 2 or 3.Preferred are substituted or unsubstituted, branched or unbranched C1 to C30 alkyl or substituted or unsubstituted aryl, and particularly preferred are substituted or unsubstituted, branched or unbranched C1 to C6 alkyl or substituted or unsubstituted C6 to C10 aryl. Most preferred is unsubstituted, branched or unbranched C1 to C6 alkyl or unsubstituted phenyl. Methyl and ethyl are particularly preferred in this respect.

[0066] Preferably modified esters are selected from the group consisting of monoalkyltrialkoxysilanes, dialkyldialkoxysilanes, trialkylmonoalkoxysilanes, monoaryltrialkoxysilanes, diaryldialkoxysilanes and triarylmonoalkoxysilanes, wherein the alkyl groups are preferably C1 to C6 alkyl groups. Preferably modified esters are selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propy-itriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3,4-epoxycyclohexyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, diethyldimethoxysilane and diethyldiethoxysilane.Particularly preferred are tetraethyl orthosilicate, tetrapropyl orthosilicate, mixtures thereof, and their oligomers or mixtures thereof. Tetraethyl orthosilicate and tetrapropyl orthosilicate, or mixtures thereof, are particularly preferred.

[0067] Aromatic solvents, the polar solvents mentioned above, or mixtures thereof are used as solvents for the isocyanate. Fatty acid esters and silicic acid esters are also suitable.

[0068] The proportion of solvent in the binder (phenolic resin plus isocyanate component) can be up to 50 wt.%.

[0069] In addition to the components already mentioned, the binder systems may contain further additives, e.g. silanes (e.g. according to EP 1137500 B1), internal release agents, e.g. fatty alcohols (e.g. according to US 4602069), drying oils (e.g. according to US 4268425), complexing agents (e.g. according to US 5447968) and additives to extend processing time (e.g. according to US 4540724) or mixtures thereof.

[0070] Common and well-known materials and mixtures thereof can be used as refractory molding material (hereinafter also referred to as molding material) for the production of casting molds. Suitable materials include, for example, quartz sand, zirconium sand, chrome ore sand, olivine, vermiculite, bauxite, chamotte, and so-called artificial molding materials, i.e., molding materials that have been shaped into spherical or near-spherical (e.g., ellipsoidal) shapes by industrial forming processes.

[0071] Examples include glass beads, glass granules, or artificial, spherical ceramic sands – so-called Cerabeads® – but also Spherichrome®, SpherOX®, or "Carboaccucast," as well as micro-hollow spheres such as those that can be isolated from fly ash, for example, aluminum silicate hollow spheres (so-called microspheres). Mixtures of the aforementioned refractory materials are also possible.

[0072] Particularly preferred are mold base materials containing more than 50 wt.% quartz sand based on the refractory mold base material. A refractory mold base material is understood to be a material with a high melting point (melting temperature). Preferably, the melting point of the refractory mold base material is greater than 600°C, more preferably greater than 900°C, more preferably greater than 1200°C, and most preferably greater than 1500°C.

[0073] The refractory molding base material preferably constitutes more than 80 wt.%, in particular more than 90 wt.%, especially preferably more than 95 wt.%, of the molding material mixture.

[0074] The mean diameter of the refractory molding materials is generally between 100 µm and 600 µm, preferably between 120 µm and 550 µm, and particularly preferably between 150 µm and 500 µm. The particle size can be determined, for example, by sieving according to DIN ISO 3310. Particularly preferred are particle shapes with a ratio of maximum to minimum longitudinal extent (perpendicular to each other and in all spatial directions) of 1:1 to 1:5 or 1:1 to 1:3, i.e., those that are, for example, not fibrous.

[0075] The refractory molding base material preferably has a free-flowing state, in particular to be able to process the molding material mixture according to the invention in conventional core shooting machines.

[0076] Suitable catalysts are tertiary amines. For the PUCB process, volatile tertiary amines are used, such as trimethylamine ("TMA", CAS RN 75-50-3), dimethylethylamine ("DMEA", CAS 75-64-9), dimethylisopropylamine ("DMIPA", CAS 996-35-0), dimethylpropylamine ("DMPA", CAS RN 926-63-6) and triethylamine ("TEA", CAS RN 121-44-8).

[0077] For the PUNB Liquid tertiary amines are used. This includes tertiary amines that are liquid at room temperature (25 °C), as well as those that become liquid after heating to, for example, 40 °C, or those that are dissolved in a suitable solvent. Examples are tris(3-dimethylamino)propylamine, N-methylimidazole, N-ethylimidazole, and 1-methylbenzimidazole.

[0078] Furthermore, the invention relates to a method for producing the molding material mixtures comprising (a) Mixing refractory molding materials with the binder according to the invention (comprising at least the phenolic resin composition and the isocyanate component) in an amount of 0.2 to 5 wt.%, preferably 0.3 to 4 wt.%, particularly preferably 0.4 to 3.5 wt.%, based on the amount of refractory molding materials, and a catalyst added simultaneously (in the PUNB process) or separately later (in the PUCB process) to obtain a molding material mixture; (b) introducing the molding material mixture obtained in step (a) into a molding tool; (c) optionally adding the separately added catalyst (PUCB) and hardening the molding material mixture in the molding tool with the catalyst according to the invention to obtain a core or a casting mold; and (d) subsequently separating the core or casting mold from the tool and optionally further hardening.

[0079] To produce the molding compound mixture, the components of the binder system can first be combined and then added to the refractory molding base. However, it is also possible to add the binder components to the refractory molding base simultaneously or sequentially in any order.

[0080] Conventional methods can be used to achieve a uniform mixture of the components of the molding compound. The molding compound may also optionally contain other conventional components, such as iron oxide, ground flax fibers, wood flour granules, pitch, and refractory metals.

[0081] According to the invention, curing can be carried out using either the PUCB or the PUNB process. In the PUCB process, a low-boiling tertiary amine is passed through the molded material mixture in gaseous form or as an aerosol using an inert carrier gas. The addition of a separate catalyst is omitted. All known cold box amine catalysts can be used. In the PUNB process, the amine or metal catalyst can already be dissolved in the binder or added to the refractory material as a separate component, with the addition amount being approximately 0.1 wt.% to approximately 5 wt.% based on the molding material mixture.

[0082] The molded parts produced by this process can, in principle, have any shape customary in the field of foundry work. In a preferred embodiment, the molded parts are in the form of foundry molds, cores, or risers. These are characterized by high mechanical stability.

[0083] The invention further relates to the use of this molded body for metal casting, in particular iron and aluminium casting.

[0084] The invention will be explained in more detail below with reference to preferred embodiments and / or experimental examples. Experimental examples

[0085] Components used (all percentages mean weight %). Benzyl ether-type 1 phenolic resin - o-cresol / phenol / cardanol copolymer, characterized by the following analytical parameters: Molecular weight (Mw) approx. 900 g / mol, OH: approx. 560 mg KOH / g, free phenol content: 1.8%, saligenin content: 3.8%, free formaldehyde content: 0.17 wt.%. ISOCYANATE COMPONENT 1 - homogeneous mixture of 80% Lupranate M 20 S and 20% linear C 10-13 alkylbenzene (CAS: 67774-74-7), supplier Sasol. ISOCYANATE COMPONENT 2: homogeneous mixture of 80% Lupranate M 20 S and 15% linear C 10-13 alkylbenzene (CAS: 67774-74-7), supplier Sasol, and 5% Ethyl acetoacetate CATALYSATOR 706 - Dimethylpropylamine, supplier ASK Chemicals GmbH Quartz sand H 32 - supplier Quarzwerke GmbH MIRATEC DC 3 - water-based sizing, flow time 12 s / 4 mm cup, supplier ASK Chemicals GmbH LUPRANAT M 20 S: polymeric MDI, functionality 2.6, supplier BASF SE DBE - Dimethyl ester mixture of C 4 - C 6 dicarboxylic acids, supplier DuPont FSE - fatty acid ester e.g.Distilled rapeseed oil fatty acid methyl ester or isopropyl ilaura 98%, supplier OLEON Silane 2201 EQ - Ureidosilane 50% in methanol, supplier Evonik Industries Malonic acid diethyl ester - supplier Sigma Aldrich Ethyl acetoacetate (EAA) - supplier Sigma Aldrich Trimethylolpropane triacetoacetate - supplier Sigma Aldrich Glyoxylic acid 50% in water - supplier Sigma Aldrich Synthro Stab TF 501 - 50% ethylene urea solution in water, supplier: Protex International Hydrofluoric acid 40%, supplier Sigma Aldrich Ketobutanoic acid - supplier AppliChem GmbH Palmer 1500-1, mixture of Cardanol and Cardol, supplier Palmer International. Benzyl ether resin 2

[0086] In a reaction vessel equipped with a stirrer, reflux condenser, and thermometer, 698.4 g of phenol (99%), 302.6 g of paraformaldehyde (91%), and 0.35 g of zinc acetate dihydrate were placed. With stirring, the temperature was increased uniformly to 105–115 °C over 60 minutes and held until a refractive index (at 25 °C) of 1.5590 was reached. Then, 50 g of Palmer 1500-1 were added, the condenser was switched to atmospheric distillation, and the temperature was raised to 124–126 °C over one hour. Distillation continued at this temperature until a refractive index (at 25 °C) of 1.5940 was reached. A vacuum was then applied, and distillation was carried out under reduced pressure until a refractive index (at 25 °C) of approximately 1.600 was achieved. Subsequently, 10 parts by weight of n-butanol were added to every 90 parts by weight of the resulting resin, and the mixture was refluxed at 122–124 °C for 60 minutes. The unreacted butanol was then removed under vacuum.The resin had a refractive index (25°) of approximately 1.5970, a free phenol content of 9.8% and a free formaldehyde content of 0.2 wt.%.

[0087] Tables 1 and 2 show the prepared phenolic resin compositions based on benzyl ether-type phenolic resin (parts by weight). The free formaldehyde content was determined using the HPLC method described above.

[0088] In a Hobart mixer, a sand mixture consisting of quartz sand H 32, plus 0.60% of the aforementioned binder compositions (each individually for examples A1 to B6) and 0.60% isocyanate component 1 was homogeneously mixed for 2 minutes. This sand mixture was transferred to a Roeper H 1 core shooting machine, and two cores, each with dimensions (L x W x H) of 220 mm x 22.4 mm x 22.4 mm, were injected into the mold using compressed air at a shooting pressure of 4 bar. The sand was cured using CATALYSATOR 706 (0.5 ml, gassing time 10 s at 2 bar purge pressure). After curing, the core was removed, and its strength was determined after 15 seconds using a Multiserver bending device L Ru-2e.

[0089] To determine the coating strength, a 10-minute-old core was immersed in the water-based coating MIRATEC DC 3 for 4 seconds and broken after a 30-minute waiting period at room temperature (20 °C) (wet value). Another pair of cores was dried for 30 minutes at 150 °C in a convection drying oven after coating. After 30 minutes at 150 °C, the core was removed and, after cooling to room temperature, its flexural strength was determined using a multi-service instrument.

[0090] Table 3: shows the strengths (in N / cm²) for mixtures made from the benzyl ether resin 1. 98% represents the relative humidity. Table 3 Water level Phenolic resin component immediately 15" 24h 24h 98% wet dry A 1 185 328 267 268 387 A 2 182 325 270 265 388 A 3 186 330 255 260 375 A 4 160 240 80 91 166 B 1 180 315 205 221 328 B 2 180 322 218 223 335 B 3 180 330 221 228 346 B 4 178 331 211 215 350 B 5 175 328 221 230 356 B 6 180 326 218 222 358

[0091] Tables 1-3 show that the addition of beta-keto esters reduces the free formaldehyde content to the limit of 0.01 wt.%. This reduces the 24-hour strength, which, surprisingly, can be increased again by adding glyoxylic acid or ketobutanoic acid. Tables 1 and 3 also show that while usable strengths are achieved with ethyl malonates (example A2), the free formaldehyde content cannot be reduced below the desired limit of <0.01 wt.%.

[0092] If ISOCYANATE COMPONENT 2 is used for examples A1 to A4 and B1 to B6 instead of ISOCYANATE COMPONENT 1, the same trends are obtained as shown in Table 3 for the determination of strengths. Table 1 not according to the invention according to the invention A 1 A2 A 3 A 4 B 1 B 2 B 3 B 4 B 5 B 6 Benzyl ether resin 1 50,00 50,00 50,00 50,00 50,00 50,00 50,00 50,00 50,00 50,00 DBE 24,70 23,70 24,50 24,35 24,45 24,25 24,05 23,85 24,00 24,15 FSE 24,70 23,70 24,50 24,35 24,35 24,25 24,05 23,85 24,00 24,15 Diethyl malonic acid ester 2,00 EAA 0,70 0,40 0,70 0,70 0,70 1,20 0,40 Synthro Stab TF 501 0,50 Silan 2201 EQ 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 Hydrofluoric acid 40% 0,10 0,10 0,10 0,10 0,10 0,10 0,10 0,10 0,10 0,10 Glycoxylic acid 50% 0,40 0,20 0,20 0,60 1,00 0,20 0,20 free formaldehyde content (%) 0,085 0,040 0,082 0,003 0,009 0,005 0,004 0,004 0,001 0,002 Table 2 not according to the invention according to the invention A 5 B7 B 8 B 9 B 10 B 11 B 12 B 13 Benzyl ether resin 2 50,00 50,00 50,00 50,00 50,00 50,00 50,00 50,00 DBE 24,70 24,25 24,15 23,80 24,25 24,15 23,80 23,80 FSE 24,70 24,25 24,15 23,80 24,25 24,15 23,80 23,80 Trimethylolpropane triacetoacetate 0,70 0,90 1,20 EAA 0,70 0,90 1,20 0,70 Silan 2201 EQ 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 Hydrofluoric acid 40% 0,10 0,10 0,10 0,10 0,10 0,10 0,10 0,10 Glycoxylic acid 50% 0,20 0,20 0,60 0,20 0,20 0,60 Ketobutanoic acid 0,20 free formaldehyde content (%) 0,099 0,009 0,007 0,006 0,009 0,006 0,005 0,009

Claims

1. Phenolic resin composition comprising at least: - a polyol component, wherein the polyol component is a phenolic resin of the benzyl ether type; - a beta-dicarbonyl compound comprising the following group:         R1C(=O)-CH2-C(=O)-O-     (I) wherein R1 is H, is a C1 to C12 hydrocarbon, preferably a C1 to C7 hydrocarbon, or is -CH2-X, wherein X is a residue which, in addition to hydrogen atoms, contains 1 to 11 carbon atoms, preferably 1 to 6 carbon atoms, and 1 to 3 oxygen atoms, as a formaldehyde scavenger and / or reaction product(s) with formaldehyde thereof; and - an alpha-carbonyl-carboxyl compound with the following structure         R3O-(O=)C-C(=O)-R4     (III) wherein and R4 independently of one another, each is H or a C1 to C6 hydrocarbon, in particular C1 to C4 hydrocarbon.

2. Phenolic resin composition according to claim 1, wherein the content of free formaldehyde is from 0 wt% to 0.25 wt%, preferably 0.001 wt% to less than 0.1 wt% and particularly preferred from 0.001 wt% to less than 0.01 wt% in the phenolic resin composition.

3. Phenolic resin composition according to at least one of the preceding claims, wherein the beta-dicarbonyl compound is selected from one or more members of the group: methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, isobutyl acetoacetate, t-butyl acetoacetate, benzyl acetoacetate, dodecyl acetoacetate, ethyl benzoylacetate, 2-methoxyethyl acetoacetate, 2-acetoacetoxyethyl methacrylate, methyl-4-methyl-3-oxopentanoate, and trimethylolpropane triacetoacetate.

4. Phenolic resin composition according to at least one of the preceding claims, wherein - the alpha-carbonyl-carboxyl compound is selected from one or more members of the group: glyoxylic acid, glyoxylic acid ethyl ester, 2-ketobutanoic acid and 2-ketobutanoic acid methyl ester; and / or - the alpha-carbonyl-carboxyl compound is present in the composition in an amount of up to 1.0 wt%, preferably 0.01 to 0.5 wt% and particularly preferred 0.02 to 0.0999 wt%.

5. Phenolic resin composition according to at least one of the preceding claims, wherein the phenolic resin of the benzyl ether type has - a water content of 0.2 to 0.9 wt%, particularly preferred of 0.3 to 0.9 wt% and especially preferred of 0.4 to 0.9 wt%; and / or - an OH number according to DIN 53240 of 500 to 900 mg KOH / g, preferably of 550 to 850 mg KOH / g and particularly preferred of 560 to 750 mg KOH / g; and / or - an average molecular weight determined as a weight average according to DIN 5567-1 by means of GPC of 500 to 1100 g / mol and in particular 550 to 1000 g / mol and in particular preferably of 560 to 980 g / mol, calculated without phenol and monomeric phenol-formaldehyde addition products.

6. Phenolic resin composition according to at least one of the preceding claims, wherein the beta-dicarbonyl compound and / or the reaction product thereof is contained in the composition in an amount of up to 1.5 wt%, preferably 0.1 to 1.0 wt% and particularly preferred 0.15 to 0.9 wt%.

7. Phenolic resin composition according to at least one of the preceding claims, wherein the phenolic resin composition has a free phenol content of less than 12 wt%, preferably less than 10 wt% and particularly preferred less than 2 wt%, in each case based on the phenolic resin of the benzyl ether type.

8. Phenolic resin composition according to at least one of the preceding claims, wherein the phenolic resin composition further comprises saligenin, in particular in a weight ratio of free phenol to saligenin of 1:1.1 to 1:12, more preferably of 1:1.5 to 1:10 and most preferably of 1:1.8 to 1:8.

9. Phenolic resin composition according to at least one of the preceding claims, wherein the solvent for the polyol component is a dicarboxylic acid ester and / or a fatty acid ester and preferably contains less than 10 wt% of aromatic solvents.

10. Phenolic resin composition according to at least one of the preceding claims, wherein the phenolic resin composition - comprises 30 to 90 wt%, preferably 35 to 85 wt% and in particular 40 to 80 wt% phenol resin of the benzyl ether type; and / or - comprises more than 95 wt% exclusively phenol resin of the benzyl ether type and solvent, including optionally present diluent.

11. Binder composition comprising at least: - the phenolic resin composition according to at least one of the preceding claims; and - an isocyanate component comprising one or more isocyanate compounds with at least 2 isocyanate groups per molecule.

12. Binder according to claim 11, wherein the binder contains, also independently of one another, - 8 to 70 wt%, in particular 10 to 62 wt%, of phenolic resin of the benzyl ether type; - 13 to 78 wt%, in particular 17 to 70 wt%, of isocyanate compounds; and - 2 to 57 wt%, in particular 3 to 53 wt%, solvent for the phenolic resin of the benzyl ether type and the isocyanate compounds.

13. Molding material mixture containing the components of the binder according to at least one of the preceding claims 11 or 12 and a refractory molding base material, wherein the refractory molding base material is selected from one or more members of the group consisting of olivine, chamotte, bauxite, aluminum silicate hollow spheres, glass beads, glass granulate, synthetic ceramic molding base materials, and silicon dioxide, in particular in the form of quartz sand, zircon sand, or chrome ore sand.

14. Molding material mixture according to claim 13, wherein the binder is present as a kit comprising, separately from one another, at least the isocyanate compounds as one component and the phenolic resin of the benzyl ether type as a further component.

15. Method for producing a molded body as a casting mold, core, or feeder, comprising (i) preparing the molding material mixture according to at least one of claims 13 or 14; (ii) introducing the molding material mixture or its components into a molding tool; (iii) hardening the molding material mixture in the molding tool with at least one tertiary amine to obtain a hardened, self-supporting molded body; and (iv) subsequently separating the hardened, self-supporting molded body from the molding tool and, optionally further hardening thereby obtaining a cured molded body.

16. Method according to claim 15, wherein the tertiary amine is selected from one or more members of the group: trimethylamine, dimethylethylamine, dimethyl-n-propylamine, dimethyl-iso-propylamine, diethylmethylamine, triethylamine, tri-n-propylamine, tri-isopropylamine, tri-n-butylamine, triisobutylamine, tris(3-dimethylamino)propylamine, N-methylimidazole, N-ethylimidazole, and 1-methylbenzimidazole.

17. Casting mold, core, or feeder manufactured according to the method of claims 15 or 16.

18. Use of the casting mold or core manufactured according to the method of claims 15 or 16 for metal casting, in particular iron or aluminium casting.