EP4178742A1 - Moulding material for producing cores and method for curing same - Google Patents

Abstract

The invention relates to a moulding material for producing cores using the cold box method, comprising the following components: a two-component, phenol- and phenol-derivative-free, polyurethane-based binder, containing a resin component, having one or more branched aliphatic or aromatic polyester polyols, formed by branched aliphatic or aromatic diol or triol starters with one or more side chains, as well as substituted or unsubstituted aliphatic and/or aromatic di- and/or tri-carboxylic acids or anhydrides thereof and/or one or more polycarbonate alcohols with equivalent weights of 250 to 4000 g/val and hydroxyl functionalities of 2 to 4 as compounds that are hydrogen-active relative to isocyanates, wherein the branched polyester polyols and/or polycarbonate alcohols of the resin component of the binder have a proportion in the region of 35 to 100 wt.% of the resin component; and a curing component, having one or more polyisocyanates; as well as one or more refractory, loose-fill filling materials. The invention also relates to a method for curing a moulding material of this type. The moulding material can be cured in the cold box method via a gas application with tertiary amines in short cycles. The option of replacing usual phenolic urethane resin binders achieves considerable emission advantages in casting-related binder burn-off.

Description

Molding material for the production of cores and process for its hardening

The invention relates to a molding material for producing cores in the cold box process. This molding material includes natural and/or ceramic sand and a two-component polyurethane binding agent that is free of phenol and phenol derivatives. Furthermore, the invention relates to a method for curing this molding material. The molding material can be cured in the cold box process by gassing with tertiary amines in short cycle times. The possibility of replacing phenolic urethane resin binders that have been used up to now means that considerable emissions advantages are achieved in the case of binder burn-off caused by casting.

Gassing-hardening processes for core production in non-heated core boxes are generally referred to as cold-box processes. In particular, the PU cold box process (phenolic urethane cold box or polyurethane cold box) has become established since its introduction in the 1960s. It is currently the most widespread core manufacturing process, which is why it is simply used under the term "cold box" in foundry parlance. For the sake of simplicity, the abbreviation “cold box process” is also used within the scope of this disclosure document when talking about the gassing-hardening PU cold box process.

The widespread use of the process is due to process advantages such as very short curing times combined with high molding material strength and good casting results. The cores are generally made with a special core shooter. The molding material, which consists of a mixture of basic molding material, resin and hardener, is introduced into an unheated core box and compressed using compressed air from the machine's shooting head. The molding material is hardened by passing an amine-carrier gas mixture through the core box. The carrier gas is generally Air, but can also be an inert gas such as nitrogen or argon. Then excess amine is flushed out of the core box with compressed air. The molding material core obtained in this way has a sufficiently high initial strength to be removed from the core box without distortion. During storage until casting, the core is post-cured until the molding material has reached its so-called ultimate strength.

The hardening of the molding material catalyzed by tertiary amines enables short core production cycle times, so that the process is primarily used for large series and automated processes in foundries.

Cold box binders are two-component binders consisting of a polyol-containing resin component and an isocyanate-containing hardener component, which react to form the polyurethane when the molding material hardens.

Cold box binders currently on the market generally consist, as described in US Pat. No. 3,409,579 A, of phenol-formaldehyde resins in a solvent as the polyol component and a hardener component of an aromatic polyisocyanate in a suitable solvent. The solvents used are usually volatile aromatic hydrocarbons. Volatile, tertiary amines such as triethylamine in gaseous form are used to quickly harden the molding material in the core box. Phenol-formaldehyde resins are hydroxy-functional polyols formed by the condensation of mono- or polyhydric phenols with aldehydes, especially formaldehyde. The reaction proceeds with acidic catalysis in such a way that so-called novolaks are formed, and with base catalysis to form resol resins.

In a further development, the so-called Cold Box Plus process, the core box is heated to 40 to 80 °C, which results in faster binder crosslinking on the outside of the core. Strength and moisture resistance of the cores are thus compared to the regular Cold box process significantly increased.

Volatile, tertiary amines such as trimethylamine, triethylamine, dimethylethylamine or dimethylpropylamine are used as amines for catalysis in the cold box process. EP 2 106310 B1 describes mixtures of at least two tertiary amines, mostly as a combination of higher and lower boiling amines, as being advantageous for handling and curing the molding material. The amount of amine required is reduced compared to using the higher boiling point amine, while the odor load is lower than when the low boiling point amine alone is used.

Phenolic resin-based cold-box binders contain various additives and additives in addition to the components that are essential for curing: phenolic resin, polyisocyanate and catalyst. Acidic additives are added to the components to ensure that the molding material has a long processing life. In US Pat. No. 4,540,724 A, phosphorus halides such as phosphoryl chloride are used for this purpose. The use of chlorosilanes to increase the lifetime of the sand is described in DE 3405 180 A1. The disadvantage here is that chlorine-containing compounds can decompose with the release of hydrochloric acid. This is hazardous to health and also corrosively attacks the surrounding metal parts. A variant that is less harmful to health is described in DE 102012201 971 A1. Mixtures of methanesulfonic acid, phosphoric acid esters and silanes are added to the isocyanate-containing component, which allows the sand to be extended and its storage stability to be increased.

According to WO 001985004603 A1, the open time of cold-box binders based on phenolic resin and isocyanate can be extended to up to 4 hours by adding phosphorus-containing acids and derivatives thereof. According to DE 4327292 A1, adhesion promoters such as alkoxysilanes are used to improve the adhesive effect of the binder in the refractory filler and the storage stability of the core obtained.

In various stages of development of the phenolic resin-based cold box binder systems, a significant influence of the thinners of resin and hardener components on curing speeds and strength was described. As explained in WO 002016038156 A1, an attempt was also made to improve the environmental compatibility of the binder, in particular the BTX emission, by replacing aromatic, highly volatile hydrocarbons as the solvent.

DE 2906052 A describes a cold box binder in which the resin component comprises a phenolic resin which is diluted with a mixture of aromatic hydrocarbon and a phosphate and/or carbonate ester. This solvent variation achieves an increased curing speed and increased heat resistance of the cores. The aromatic solvents, which are hazardous to health, could not be dispensed with completely.

In US Pat. No. 3,905,934 A, various dialkyl phthalates were used as solvents to reduce the odor pollution caused by aromatic hydrocarbons. However, numerous representatives of this class of substances have now been classified as toxic to reproduction. Furthermore, the aromatic load remains almost unchanged compared to the binders previously used.

DE 19542752 A1 discloses the use of rapeseed methyl ester or dibasic ester as a thinner for the resin and/or hardener component of a cold box binder, as a result of which aromatic hydrocarbons that are harmful to health can be completely replaced during processing. As other benefits of rapeseed methyl ester are a good Separation effect between mold and core as well as low outgassing during casting are described.

In DE 19925115 A1, alkyl silicates are used as solvents for phenolic resin and isocyanates, in particular tetraethyl orthosilicate. This avoids the emission load that comes from the aromatic solvents otherwise used, without any disadvantages for the other binder properties. Casting properties are even improved as the thermal resistance of cores and molds is very high and lower gas pressure development is observed. However, as explained in WO 2011008362 A1, alkyl silicates also have disadvantages. They contaminate the acidic solution in the downstream amine scrubber through gel formation and can release finely divided white silicate particles during processing of the molding material, which are released into the air as suspended matter. In addition, tetraethyl silicate has an intensely pungent odor and is classified as an eye and respiratory tract irritant and harmful if inhaled.

DE 102015201 614 A1 describes that classic polyurethane binders contain aromatic substances in both components, namely the phenolic resin and diphenylmethane diisocyanate. BTEX aromatics such as benzene, toluene and xylenes are therefore released during casting. This emission load can be reduced by reducing the amount of binder in the molding material. This is accompanied by a lower nitrogen content in the binder and a reduced risk of nitrogen-induced casting defects such as so-called pinholes occurring. Furthermore, alkyl silicates and dibasic esters as solvents for resin and hardener components ensure lower BTEX emissions and less odor pollution.

WO 2011008362 A1 describes a cold box system in which the resin consists of a phenolic resin, polyetherpolyol, polyesterpolyol, an aminopolyol or mixtures thereof, phenolic resins being preferred. When Solvents are necessarily used in resin and/or hardener cycloalkanes, which are said to bring about positive properties such as improved casting quality. Only a binder containing phenolic resin is disclosed in the examples. The other polyol types are listed in the descriptive part, but their actual suitability is not proven with examples.

In addition to the solvents, the phenolic resins themselves, or their production-related unavoidable monomer content of the toxic CMR substances formaldehyde and phenol, which can be carcinogenic, mutagenic or toxic to reproduction, pose a significant burden on the environment and the health of the processor in all steps of molding, through casting to landfilling of the molding material. A number of publications list efforts to avoid their release.

According to DE 102008055042 A1, the phenol content is reduced by using modified phenolic resins. In this case, free hydroxy functions of the phenolic resin units are linked or substituted by esters of orthosilicic acid and its polymers. The advantages are, among other things, reduced odor nuisance, fewer pollutant emissions and increased thermal resistance. Furthermore, some phenol is replaced by cresols (methylphenol), which are not CMR substances but are still toxic.

In DE 102018 100694 A1, combinations of β-dicarbonyl compound and an α-carbonyl-carboxyl compound, in particular glyoxylic acid, are used as so-called formaldehyde scavengers in phenolic resins of the benzyl ether type. This means that the proportion of free formaldehyde can be reduced to less than 0.01%. The addition of glyoxylic acid does not affect the stability of the phenolic resin and the free formaldehyde content remains relatively low. However, greatly reduced levels of free formaldehyde are generally associated with a loss of strength in the cured molding material. According to DE 102006037288 B4, the contents of free phenol and formaldehyde can be significantly reduced by adding cardol and/or cardanol or their derivatives. At the same time, the moldings produced from these resins have high thermal stability.

The reduction of the formaldehyde content of a phenolic resin, which can be used both in the no-bake and in the cold-box process, was described in DE 69207275 T2 by introducing aliphatic hydroxyl compounds such as ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, triethylene glycol, glycerin, sorbitol and polyether polyols with a hydroxyl number greater than 200.

A further disadvantage of phenolic resin-based cold box systems is a high tendency to casting defects due to so-called veining or hot cracking in gray and steel castings. These casting defects can be partially avoided by organic (wood flour) or inorganic mold material additives (iron oxide). However, the additives themselves cause undesired effects. The emission load during casting is significantly increased by organic additives and gas-induced casting defects therefore occur more frequently. The inorganic additives, on the other hand, accumulate in the regenerated sand and thus lower the sintering point of the molding material, which is undesirable with regard to the casting and can also lead to casting defects.

In DE 2348226 A1, part of the phenolic resin is replaced with aliphatic or aromatic polyether alcohols in order to reduce the tendency towards casting defects when using cores produced in the cold box process. In order to achieve a sufficiently high reaction rate, phenol and benzyl alcohol derivatives with a low molecular weight are also necessary. The resin component used continues to consist largely of phenol-based substances. WO 001990005155 A1 describes a polyurethane binder based on phenol-formaldehyde resin and polyisocyanate which, by adding 2.0 to 8.0% polyester polyol based on the weight of the phenolic resin component, has improved decomposition properties of a molding material produced therewith. It is therefore particularly suitable for casting with low-melting metals such as aluminium. Furthermore, a flattening of the molding material by gaseous amines according to the cold box process is described.

The term cold box can also be used for other gas-curing processes, for example urea-formaldehyde or phenol-formaldehyde resins that are cured with sulfur dioxide. DE 102005024334 A1 discloses a multi-component system consisting of epoxy resin, an unsaturated ethylene compound, a saturated fatty acid and radical initiators, which is cured with sulfur dioxide. The epoxy resins used are mostly based on bisphenol A, which has been shown to damage fertility in humans and is therefore no longer allowed to be used in the manufacture of everyday objects. Furthermore, cores that _{were produced using the SO 2} cold box process deform under thermal stress, which is an undesirable effect when the cores are oven-dried after so-called sizing.

Another gas-hardening molding material process is based on sodium silicate binders. These water glasses, which are often modified, can be _{hardened in the molding material by gassing with CO 2} in relatively short cycle times. The water glass C0 ₂ process, which was developed by Leo Petrzela in 1947, is considered to be the first gassing-hardening cold box process.

In this gassing-hardening process for the production of foundry molds and cores, chemical hardening is achieved by introducing carbon dioxide into the mold material mixture containing alkali silicate. The formation of a Si0 ₂ gel, which is responsible for the actual strength, takes place in the A period of seconds to a few minutes takes place, so that high-speed production is made possible. In the 1950s and 1960s, the water glass C0 ₂ process was widespread, but was quickly displaced with the advent of the polyurethane cold box process.

One of the advantages of water glass-based binders is their silicate, non-organic structure. This means that no pollutants are emitted through VOC release or combustion during molding and casting.

For a long time, silicate binders had to contend with massive disadvantages in the casting process. When subjected to thermal stress in the cast, they show a softening point that can lead to distortion of the cast part. In addition, they accumulate quickly in the recycled molding material and thus lead to an undesirable reduction in the sintering point in the recycled molding material. Last but not least, the high pH value of used sands to be landfilled, due to their strongly basic properties, leads to classification in unfavorable and cost-intensive landfill classes. The low flowability of the molding materials restricts the ability to shoot, especially of filigree core elements, which also makes it difficult to handle thin-walled moldings due to the comparatively low strength, especially when removing the casting molds. Furthermore, the shelf life is limited in the case of increased humidity.

These chemically related disadvantages have been increasingly mitigated or eliminated in recent years by modifying and adding additives to the siliceous binder.

WO 2009056320 A1 describes surface-active surfactants, such as fatty acid sulfates, sulfonates or phosphates, which increase the flowability of the molding material.

According to DE 102012 103705 A1 be increased by displacing excess water from the molding material through thermal post-treatment. Furthermore, after the actual curing of the mold material, excess carbon dioxide can be expelled from the core by purging with a gas that contains less carbon dioxide than that used for curing. This avoids the undesired formation of strength-reducing by-products.

Organic substances are often used to promote the decomposition properties of silicate mold materials during casting. These burn during pouring. The resulting pores in the molding material structure are intended to improve the ability of the molding material to be cored out of the cast part. Typical examples of such decomposition additives are residual products from the sugar industry, such as molasses or syrup, and from the cellulose processing industry, in particular the tall oil described in DD 13105 A5. However, these lead to increased emissions during casting. Inorganic additives can also be used to positively influence the decomposition behavior of the molding material. For example, DE 102013 111 626 A1 discloses oxidic boron compounds and DE 102017 107531 A1 describes particulate phyllosilicates, which also improve coreability after casting.

Due to the aforementioned disadvantages of alternative gas-curing processes, the polyurethane cold box process for high-frequency core production in the foundry remains unchallenged. Here, too, there are already tendencies to replace the previously prevalent phenol-formaldehyde resin in the resin component of the binder with physiologically harmless compounds.

US Pat. No. 5,688,857 A describes a cold-box binder that dispenses entirely with phenolic components. Diols or triols with a maximum of four carbon atoms, for example ethylene glycol, are claimed as Flarz components. These are mixed with water, optionally a solvent and optionally a maximum of 30% polyether polyol, polyester polyol, amine-based polyols or phenolic resin.

WO 002009004086 A1 discloses what is known as an alternative cold box process which contains a glycerol ester, a saccharide, a polyol, a crude oil or mixtures of these compounds as reactive polyol components in the binder. This avoids emissions of harmful substances such as phenol, formaldehyde and aromatic solvents. Curing takes place with water or a water-amine mixture at temperatures of preferably more than 80° C. in order to reduce exposure to the amine gas at the workplace. Water is obviously necessary as a reactant for curing, which is why one cannot speak of a cold box system in the classic sense.

WO 002009065015 A1 describes a bio-based binder system in which saccharides obtained from corn syrup and molasses react with isocyanates in order to bind a basic mold material to foundry molding compounds in a self-curing process. With the exclusion of phenolic or other aromatic compounds, aliphatic monoalcohols and polyols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, hexane-1,6-diol, 2-methyl-1,3-propanediol, glycerol, mannitol, sorbitol , Diethylene glycol, triethylene glycol, polyethylene glycols, polypropylene glycols and butylene, dibutylene and polybutylene glycols are mentioned as further hydroxy-functional components.

According to DE 2039330 C3, the shelf life of cold box binders is extended by using a polyurethane-based binder whose resin component was obtained by condensation of aliphatic ketones with formaldehyde. This binder does not use phenols as hydroxy-functional resin components, but the use of aromatic solvents is described to reduce the viscosity of the resin to humiliate.

WO 002000040351 A1 describes a polyurethane binder which is made up of a polyol component consisting of a polyether polyol, glycol and aromatic polyester polyol with 5 to 35% based on the total mass of the polyol component, an organic polyisocyanate component and a liquid amine catalyst and is contained in the self-curing cold resin procedure can be applied. Although the absence of free phenol and formaldehyde is cited as an advantage of the binder, phenolic resins such as benzyl ether resins can be present in the polyol component at up to 15% by weight.

The vast majority of the disclosures mentioned above are based on molding material binders whose resin component is either made up of phenolic resins or contains aromatic compounds as diluents/solvents and/or additives.

The molding materials used to date in foundries for the production of cores in the cold box process have in common that their binders are based on phenolic resins and polyisocyanates. These enable the molding material to be cured by gassing with volatile amines in very short cycle times. Depending on the amount of molding material to be hardened, cycle times of 30 to 90 seconds are common. However, the use of phenolic resins entails considerable emissions in the production of mold material and in particular in the pyrolytic decomposition of the binder during casting. In the process, a significant proportion of the monomers from which the phenolic resins are made are released. In particular, substances that are hazardous to health and have a workplace limit value, such as phenol and phenol derivatives, formaldehyde and BTEX compounds, are emitted.

In order to avoid releasing these substances during the thermal decomposition of the molding material binder, the phenolic resins and aromatic solvents of the binder must be replaced by other, non-hazardous ones Substances are replaced. Since binders based on phenolic resins and polyisocyanates are highly reactive to gassing with amines and the reaction to form the desired polyurethane polymers takes place extremely quickly, substituting phenolic resins in molding binders for the cold box process is not trivial.

DE 69331 286 T2 and DE 102015 118428 A1 disclose that aliphatic polyols can also be used on the resin side instead of the aromatic phenolic resins for self-curing molding material binders. Polyether polyols in particular are used here, but they are not reactive enough to achieve the cycle times that are usual in the cold box process through amine gassing. The cycle times achieved with this are regularly several minutes.

The object on which the present invention is based is to develop a molding material that hardens with amine gas, in which the resin component of the binder is completely free of phenol and phenol derivatives and, in addition to rapid flattening and high molding material strength, also a low BTEX, phenol and emission of phenol derivatives when the molding material binder burns off as a result of casting.

The object of the invention is achieved with a molding material having the features of claim 1. This molding material can be hardened by supplying amine gas and is suitable for the production of cores using the cold box process. Further developments are specified in the claims dependent on claim 1.

The molding material according to the invention comprises at least one two-component, phenol- and phenol-derivative-free binder based on polyurethane and one or more refractory pourable fillers. According to the concept, other non-phenolic polyols are used instead of phenols and phenol derivatives, which have a similarly high reactivity as the Have phenolic resins.

The binder contains a resin component as a mixture of one or more branched aliphatic or aromatic polyester polyols built up from branched aliphatic or aromatic diol or triol starters with one or more side chains and substituted or unsubstituted aliphatic and/or aromatic di- and/or Tricarboxylic acids or their anhydrides, and/or one or more polycarbonate alcohols with equivalent weights of 250 to 4000 g/eq and hydroxy functionalities of 2 to 4 as hydrogen-active compounds with respect to isocyanates, the branched polyester polyol(s) and/or polycarbonate alcohols of the resin Component of the binder have a proportion in the range of 35 to 100 wt .-% of the resin component, and a hardener com component with one or more polyisocyanates. In addition, the mixture can contain further compounds with hydroxyl and/or mercapto and/or amino and/or carbamide groups which are hydrogen-active in relation to isocyanates.

According to a preferred embodiment of the invention, the resin component contains hydrogen-active individual compounds with regard to isocyanate, the resin component having an average functionality of 1.8 to 4.0 with regard to all of these hydrogen-active individual compounds, and optionally additives such as one or more diluents and optionally one or more liquid catalysts affecting the polymerization. The hardener component comprises one or more isocyanates, which preferably have at least functionality 2, and can also contain one or more diluents as additives. The number of specific functional groups in the relevant molecule is referred to here as the functionality of a compound. In the case of isocyanates, functionality refers to the number of NCO groups in a molecule. For the compounds that are hydrogen-active with respect to isocyanates, such as the polyols, the sum of OH, NH and SH groups in a molecule is taken as the functionality designated.

According to an advantageous embodiment of the molding material according to the invention, the other individual compounds that are hydrogen-active with regard to isocyanates can be selected from one or more substance classes, such as polyester polyols, polycarbonate alcohols, polyether alcohols, polyether polyester alcohols, polythiols,

Aminopolyether alcohols, alcohols with two or more functions, amines and carbamide compounds. The hydrogen-active compounds mentioned advantageously have OH, SH and NH functionalities of 1.5 to 8 and equivalent weights of 9 to 2000 g/val, based in each case on the hydrogen-active individual compounds. Two or more of these compounds are preferably incorporated into the resin component.

In order to achieve high molding material strength and short curing times, these mixtures of hydrogen-active compounds have proven to be advantageous for the purposes of the invention. Optimal crosslinking within the polyaddition product is achieved during the polyurethane reaction, which leads to high strength of the molding material due to an optimal adhesive effect. Resin components with an average equivalent weight of 90 to 220 g/val, based on the hydrogen-active constituents, have proven to be particularly suitable for this purpose. This average equivalent weight is calculated from the percentage content of OH and/or SH and/or NH groups in the individual components, taking into account their mass fractions in the mixture. It is referred to as the total equivalent weight of the component in the examples below.

According to an advantageous embodiment of the invention, the individual constituents of the resin component are chosen so that the resin component in relation to the totality of the isocyanate hydrogen-active individual compounds has an average functionality of 2.2 to 3.5. The combination of two-functional compounds with higher-functional compounds has proven to be advantageous for optimum polymer crosslinking. Polyester polyols composed of a branched aliphatic or aromatic diol and triol starter with one or more side chains which are not hydrogen-active with respect to isocyanates, and substituted or unsubstituted aliphatic and/or aromatic di- and/or tricarboxylic acids or their anhydrides. The resin component of the molding material contains branched polyester polyols and/or polycarbonate alcohols, preferably in a proportion of 40 to 80% by weight. While polyester polyols based on linear diols or triols already result in a high reactivity of the binder when gassed with amine, it is possible with the described polyester polyols based on branched diols or triols to achieve molding material curing speeds that are comparable to those of phenolic resin-based binders in the molding material to come close.

The or at least some of the side chains of a branched polyester polyol of the molding material can be selected from the following substance classes: from aliphatics, aromatics, aldehydes, ketones, carboxylic acid esters, ethers, amines, alkyl halides, nitriles, nitrogen, oxygen and sulfur heterocycles and carboxamides.

Suitable starters for the branched polyester polyols described have the following structure: , where the radicals R ⁿ include the following chemical structures:

• R ¹ = H, (CH ₂ ) _O-5 0H, OH, aliphatic, ether, aromatic, heterocycle,

carboxylic acid ester, carboxamide, haloalkane, amine, nitrile, ketone, aldehyde or combinations thereof,

• R ² = aliphatic, ether, aromatic, heterocycle, carboxylic acid ester, carboxamide, haloalkane, amine, nitrile, ketone, aldehyde or combinations thereof,

• R ³ = H, (CH ₂ ) _O-5 OH, OH, aliphatic, ether, aromatic, heterocycle,

carboxylic acid ester, carboxamide, haloalkane, amine, nitrile, ketone, aldehyde or combinations thereof,

• R ⁴ = H, aliphatic, ether, aromatic, heterocycle, carboxylic acid ester,

carboxylic acid amide, haloalkane, amine, nitrile, ketone, aldehyde, or combinations thereof, and the methylene linkages can have 0 to 5 carbons (x,y,z = 0 to 5). Examples of divalent starters according to the described

Structural formula are with a C2 distance of the hydroxy functions 2-phenyl-1,2-propanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1 ,2-octanediol, 1,2-decanediol, 3-bromo-1,2-propanediol, 1,4-dibromo-

2,3-butanediol, 3-chloro-1,2-propanediol, 2,3-butanediol, hydrobenzoin, pinacol; with a C3 distance of the hydroxyl functions 2-methyl-1,3-propanediol, 2,4-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dibutyl-1,3-propanediol, 2,2-diisobutyl-1,3- propanediol, 3-methyl-1,3-butanediol, 1,3-butanediol, 1,3-octanediol, 1,3-nonanediol, 2,2-dibenzyl-1,3-propanediol, 2-phenyl-1,3- propanediol, 1-phenyl-1,3-propanediol, 2-benzyloxy-1,3-propanediol, 2,2-bis(bromomethyl)-1,3-propanediol, diethylbis(hydroxymethyl)malonate, 2-ethyl-1, 3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,4-dimethyl

2,4-pentanediol, 2-methyl-2,4-pentanediol (hexylene glycol); with a C4 distance of the hydroxy functions 2-methyl-1,4-butanediol, 1,4-pentanediol, 2,5-hexanediol,

2,5-dimethyl-2,5-hexanediol, 2,7-dimethyl-3,6-octanediol, 2,3-dibromo-1,4- butanediol; with a C5 distance of the hydroxyl functions 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,5-hexanediol, 2,4-diethyl-1,5-pentanediol. Examples of trivalent starters according to the structural formula described are 3-methyl-1,3,5-pentanetriol, trimethylolpropane, trimethylolethane, 1,2,3-pentanetriol. The carboxylic acids fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, malic acid, tartaric acid, tatric acid, aspartic acid, glutamic acid, oxaloacetic acid and optionally are suitable for the production of the polyester polyols their anhydrides. Equally advantageous is the use of one or more aliphatic and/or aromatic polycarbonate alcohols with an equivalent weight of 250 to 4000 g/val and hydroxy functionalities of 2 to 4 in the resin component. Polycarbonate alcohols are built up from carbonates such as dimethyl carbonate, ethylene carbonate or dipentyl carbonate and divalent crosslinkers, for example 1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or trimethylolpropane (TMP). Low-viscosity polycarbonate alcohols that are easy to process contain various types of crosslinkers. In alternative synthesis routes, carbon dioxide is polymerized with epoxides such as propylene oxide, the resulting polyols having a carbon dioxide content of up to 50%. The proportion of the above-described branched polyester polyols and/or polycarbonate alcohols in the resin components is preferably from 35 to 100% by weight and particularly preferably from 40 to 80% by weight. In addition to their high curing speed, the branched polyester polyols and the polycarbonate alcohols show an advantageous resistance to hydrolysis compared to other polyol types, which leads to good storage stability of the foundry cores and good resistance to aqueous sizes. As described above, branched polyester polyols and polycarbonate alcohols are particularly suitable as crosslinking polyols for the production of the resin component. These polyols are, for example, Desmophen® VPLS from Covestro®, Oxyester® from Evonik®, Kuraray® polyol from Kuraray®, Duranol™ by Asahi Kasei®, Placcel® by Daicel®, Converge® Polyol by Saudi Aramco®, Durez®-Ter by Sumitomo Bakelite®, Eternacoll® by Ube®, Nippolan® by Tosoh®, Oxymer® by Perstorp®, Polyol CA ® from Chanda Chemical® and Hoopol® from Synthesia®. Desmophen® C 1100, C 1200, C 2102, C 2202, C XP 2760, C XP 2613, VP LS 2249/1, VP LS 2328, Oxyester® EP-HS 2272, Kuraray® Polyol C-590, C -1090, C-2090, C-3090, F-510, F-1010, F-2010, F-3010, P-510, P-1010, P-2010, P-3010, P-4010, P-5010 , P-6010, Duranole™ T5650 E, T5650 J, T5651 , T5652, G3450, G3452, G4772, Placcel® CD 205 PL, CD 220 PL, Converge® Polyol 212-10, 212-20, CPX-2001-112, 2501-56, 2502-56,

Durez®-Ter S1015-35, S1015-62, S1015-120, S1016-55, S1016-110, S1016-120, S1063-35, S1063-55, S1063-72, S1063-120, S1063-210, S1151- 22 S1157-40 S1160-35 EP092-30 S2000-55 S2000-120 S2000-250 S2001-120 S2005-55 S2006-55 S2006-120 S2006-250 Eternacoll® PH- 50, PH-100, PH-200, PH-300, Nippolan® 982R and Oxymer® M112, HD112, HD56, Polyol CA® 6010, 6020, 6040, 6050, 6410, 6420, 6440-N, Hoopol® F-601 , F-690, F-10201, F-10670, F-20013 and F-9690.

Unbranched aromatic or aliphatic polyester poles are also used. These are, for example, Hoopol® from Synthesia®, Boltorn® and Capa® from Perstorp®, Polyol CA® from Chanda Chemical®, Desmophen® from Covestro®, Diexter® and Isoexter® from Coim®, Domopol® from Helios®, Durez®- Ter from Sumitomo Bakelite®, Dynacoll® from Evonik®, Elapol® from Elachem®, K-POL® from King Industries®, Kuraray® Polyol from Kuraray®, Lupraphen® and Sovermol® from BASF®, Petopurol® from Petopur®, Placcel ® by Daicel®, Polios® by Purinova®, Polyol SP® by Caspian Chemical®, Rexin® by Sapici®, Stepanpol® by Stepan®, Terate® by Invista®, Terol® by Huntsman®, TRI-REZ® polyol by Geo Specialty® and WorleePol® by Worlee®.

Hoopol® F-390, F-1360-A, F-4350, F-4361, F-4395, F-5321, Boltorn® P1000, Capa® 2043, 2047A, 3022, 3031, Polyol CA® 5010, Desmophen® 1652, Diexter® DG5307, PL50375, Isoexter 4531,

Durez®-Ter S1153-240, S1153-300, F1049, K-POL® 8211,

Kuraray® Polyol N-2010, Lupraphen® 1901/1, 5610/1, 5619/1, 6601/3, Petopurol® 260, 300, Placcel® 205, 303, 305, 410, Polios® 250, 300, 420, polyol SP®-320GA, Rexin® DP412, HSP 50, Stepanpol® PC-5130-160, PDP-70, PS 2352, PS 3152 T 401, Terate 7541 LOV-MP, HT 5511, TRI-REZ® Polyol 1220A, 1230- 60 and WorleePol® 165.

Also advantageously suitable polyol compounds are two- to five-functional polyether alcohols. Such polyols are, for example, Voranol® from Dow Chemical®, Desmophen® from Covestro®, Lupranol® from BASF®, Isoter® from Coim®, Puranol® from Jiahua®, Lipoxol® from Sasol®, polyglycol from Clariant® and polyols from Perstorp ®. Particularly suitable are, for example, Voranol® CP 260, CP 6055 and P400, Desmophen® 1262 BD, 1300 BT, 1380 BT, 4051 B, 5031 BT, 21 AP25, Lupranol® 1000/1, 1100, 1200, 2043, 2070, 2072, 2090, 2095, 3300, 3423, 3424, 3504/1, 3505/1, Isoter® 804SA, 803SA, 809SA, 840G, 860T, Puranol® R3776, F3020, G303, G305, TMP850 and Polyol 3165, 3380, 4680, 4605/1 The Thioplast® types from Akzo Nobel® and the Thiocure® range from Bruno Bock have proven themselves as hydrogen-functional, sulphur-containing additives. Polyetherdiamines such as Jeffamine® D-400 and D-230 from Huntsman® or compounds such as diglycolamine can be used as NH-functional compounds. Diols such as ethylene glycol, 1,3-propanediol, 2-butyl-2-ethylpropanediol, 2-methyl-1,3-propanediol,

Neopentyl glycol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 2,2,4-trimethylpentane-1,3-diol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,6-hexanediol and 2-ethylhexane-1,3-diol, triols such as glycerol, trimethylolpropane, triethanolamine, tetrols such as pentaerythritol or di(trimethylolpropane) and mono- and polysugars such as glucose, sucrose and sorbitol are used. Depending on the composition of the resin and hardener components and the desired processing time in the core manufacturing process, the binders are processed with or without additional catalytic support. For this purpose, liquid or solid tertiary amine catalysts and/or metal-based catalysts or organometallic compounds which accelerate the polyurethane reaction are advantageously used as catalysts. In contrast to the volatile compounds used in amine gas curing, the following catalysts have a boiling point greater than 120 °C and are included as part of the resin component and/or added to the molding material as an individual component. Organotin, organobismuth, organozinc, organopotassium and organoaluminum compounds and tertiary nitrogen-containing substances such as dimethylcyclohexylamine, N-substituted pyrrolidones, N-substituted imidazoles, diazabicyclooctane and triazine derivatives are suitable as catalysts. Suitable metal-based catalysts are for example the Kosmos® and DABCO® types from Evonik®, TIB KAT® from TIB® Chemicals, K-Kat® products from King Industries®, the Borchi® Kat series from Borchers® and Tytane® by Borica. A comprehensive selection of catalysts with tertiary nitrogen is offered by BASF with the Lupragen® series, Lanxess® with Addocat® types, Momentive with Naix® types, Evonik® with Tegoamin® and DABCO® types, and Huntsman® with the Jeffcat® range.

Particularly suitable isocyanates of the hardener component of the molding material according to the invention are oligomers or polymeric derivatives of the basic type of 2,4'- and 4,4'-diphenylmethane diisocyanate and/or oligomers or polymeric derivatives of the type of 2,4'- and 4, 4'-dicyclohexylmethane diisocyanates and/or oligomeric or polymeric derivatives of hexamethylene diisocyanate and/or isophorone diisocyanate and/or its derivatives, as well as the aromatic, aliphatic and cycloaliphatic isocyanates prepared in a prepolymer process and their oligomers and polymers. Oligomeric and polymeric derivatives of isocyanates include carbodiimides, isocyanurates, biurets, uretdiones, and uretonimines. Preferably they have Isocyanates have at least a functionality of 2.0 and are liquid at room temperature. Furthermore, isocyanate prepolymers can be used in the hardener component. These are produced by pre-crosslinking difunctional or polyfunctional polyols in a stoichiometric deficiency with suitable aliphatic and/or aromatic and/or cycloaliphatic isocyanates. These prepolymer components preferably contain a residual content of free isocyanate groups of 15 to 30%, particularly preferably 18 to 25%. They have a maximum viscosity of 900 mPas, preferably 300 to 600 mPas, at 20.degree. This enables good mixing of the hardener component with the basic molding material. The isocyanate content of the hardener component in the molding material is advantageously chosen in relation to the hydrogen-active compounds of the resin component in such a way that free NCO groups of the hardener component and OH and/or NH and/or SH Groups of the resin component are present in a molar ratio of 0.8 to 1.2. Suitable isocyanates for binders of a molding material according to the invention include Lupranat® types from the BASF® product range, Desmodur® types from Covestro®, Voranate® types and Isonate® types from Dow Chemical®, Vestanat® Types from Evonik®, the Suprasec® series from Huntsman®, Tolonate™ types from Vencorex®, Polurene® types and Hydrorene® types from Sapici® or also Ongronat® types from Wanhua®. The suitable isocyanates mentioned above include, in particular, Lupranat® M 70 R, Lupranat® MM 103, Lupranat® M 105, Lupranat® MIP, Lupranat® M 10 R, Lupranat® M 20 S, Desmodur® 44 V 70 L, Desmodur® 44 V 20 L, Desmodur® CD-S, Desmodur® DN, Desmodur® I, Desmodur® W/1 , Vestanat® IPDI, Vestanat® H12MDI, Vestanat® TMDI, Vestanat® HT 2500/LV, Suprasec® 2030, Suprasec® 2085 , Tolonate® HDB LV, Tolonate® HDT LV, Ongronat® 3800, Ongronat® CR-30-20, Ongronat® CR-30-40, Ongronat® CR-30-60, Voranate® M229 and Voranate® M600.

The binder components of the molding materials according to the invention, ie resin and hardener, are preferably through with the aim of good processability Thinner added. Such diluents are, for example, fatty acid esters based on renewable raw materials, such as transesterification products from vegetable oils, especially their methyl, ethyl, propyl, isopropyl, butyl, isobutyl and ethylhexyl esters. Also suitable are synthetic mono-, di- and tricarboxylic acid esters, organosilicates, sulfonic acid esters, non-cyclic alkanes/paraffins as fractions from petroleum processing, phosphoric acid esters, cyclic and non-cyclic carbonates and/or non-hydroxy-terminated polyethers. Examples of fatty acid esters from natural oils are rapeseed methyl esters, the palm and soya methyl esters from Cremer®, the Priolube® types from Croda®, the DUB® products from Stearinerie Dubois®, and the RADIA® esters from Oleon®. The product ranges of Oxsoft® and Oxblue® esters from Oxea®, dibasic esters from Du Pont®, Softenol® esters from Sasol®, the Jayflex® products from Exxon®, those with Freeflex ® dibenzoate esters from Caffaro® or plasticizers from BASF®, such as Flexamoll® DINCFI or Plastomoll®. Examples of suitable cyclic and non-cyclic carbonates, such as propylene carbonate, are the Jeffsol® variants of Fluntsman®. Examples of suitable organosilicates, in particular alkyl silicates and alkyl silicate oligomers, are tetraethyl silicate, tetra-n-propyl silicate and mono-, di- and trialkyl silicates from Wacker®, Evonik® and Dow Corning®.

Intensive mixing of the individual components for the Flarz or hardener component of the binder at room temperature and with the exclusion of moisture results in the respective components with processing-friendly viscosities of 200 to 900 mPas at 20 °C for the Flarz component and 100 to 600 mPas at 20 °C C for the Flarter component. The Flarz component of the binder has 45 to 100% by weight, preferably 70 to 90% by weight, of hydrogen-active compounds and the Flarter component of the binder has 60 to 100% by weight, preferably 75 to 90% by weight. polyisocyanates. The two-component binders described in combination with refractory and pourable fillers are suitable for producing a molding material according to the invention. These natural and ceramic foundry sands are commonly referred to as basic molding materials. They include quartz sands of various origins and grain shapes, chromite sand, zircon sand, olivine sand, R sand, magnesia, alkali and alkaline earth halides, aluminum silicates such as J sand and Kerphalite®, synthetic sands such as Cerabeads®, fireclay, M sand, Alodur ®, bauxite sand, silicon carbide, expanded and foam glass, fly ash and other special sands. The preferred mean grain size is in the range from 0.1 to 0.9 mm. The binder and catalyst content in the mold material must be optimized taking into account the respective grain spectrum and the specific sand weight and is preferably 0.3 to 4.0% binder, based on the mold base material, and 0.001 to 2.5% catalyst, based on the resin component, discontinued. The invention is not limited to these settings and amounts.

The amine gas-hardening molding material can be produced from one or more refractory pourable fillers at 96.0 to 99.7% and a binder at 0.3 to 4.0% in a batch or continuous mixer. The resin and hardener components of the binder can be added in a mixing ratio of 2.5:1 to 1:2.5, depending on the respective recipe. However, for practical use in foundries, it has proven to be useful to formulate the binder systems in such a way that they can be used in a mixing ratio of 1:1, based on the mass. The molding material is then introduced from a storage vessel into a core tool by applying compressed air at 2 to 7 bar and compressed, then cured in the core tool by a carrier gas-amine mixture, which preferably contains volatile, tertiary amines. The temperature of the carrier gas/amine mixture is preferably in the range from 15 to 100.degree. After another flushing process with the carrier gas, the hardened molded part can be removed from the core tool without distortion be expelled.

Examples of suitable volatile tertiary amines are trimethylamine, triethylamine (TEA), dimethylethylamine (DMEA), diethylmethylamine (DEMA), dimethylpropylamine (DMPA), dimethylisopropylamine (DMIPA) or mixtures of several amines. The amines used are bases and have a pK _B of 1 to 10, preferably 2 to 5. The carrier gas is generally air but can also be an inert gas such as nitrogen or argon.

Disadvantages of the previous cold-box binder systems, such as formaldehyde and phenol vapors released during core production or disruptive water released by a condensation reaction, are avoided when using a molding material mixture according to the invention.

Furthermore, a molding material according to the invention does not contain any harmful aromatic solvents. Instead, preference is given to using fatty acid esters based on renewable raw materials, synthetic carboxylic acid esters, aliphatic carbonates and/or organic silicon compounds which do not contain any volatile components. The binders and the molding materials themselves have advantageous processing properties such as odorlessness, low vapor pressure, low viscosity, good flowability, rapid hardening processes and high flexural strength. The cores and molds produced with the molding materials described lead to advantageous casting properties and good disintegration. During casting, emissions of volatile organic compounds such as aromatic hydrocarbons and formaldehyde are also significantly reduced compared to binders based on phenol-formaldehyde resin.

Further details, features and advantages of configurations of the invention result from FIG. 1 and the following description of exemplary embodiments. It shows the Figure 1: A comparison of binder emissions among pyrolytic

Decomposition conditions of binders suitable for the invention (Examples 1 and 7) with a cold box binder not according to the invention (Example A2) based on phenol-formaldehyde resin.

FIG. 1 shows a comparison of the emissions from binders (Examples 1 and 7, see below), which can be used in a molding material according to the invention, with a commercial, non-inventive, phenolic resin-based cold box binder (Example A2). The measurements provide information about the chemical compounds formed during thermal decomposition of the binder under pyrolytic conditions. These are broken down as a percentage of the total quantity of emission products and classified according to substance class. For this purpose, measurements were carried out using the pyrolysis GC-FID or the pyrolysis GC/MS method at a decomposition temperature of 900°C. This method is established for the laboratory investigation of the pyrolytic decomposition products of polymers, such as the binders investigated here. It therefore provides a good approximation of the emissions to be expected under real casting conditions due to thermal decomposition of the binders in the molding material. With the same amount of binder used, there are significant differences in the composition and amount of substance of the classes of substances formed between the binders from example 1 and example 7 that can be used for the invention compared to the non-inventive, phenolic resin-based cold box binder, see example A2. In particular, the proportion of volatile aromatics (BTEX) and phenols is significantly higher in the case of phenolic resin-based binders than in binders according to Examples 1 and 7. Since chemical compounds in particular of these substance classes are classified as hazardous to health and/or CMR substances according to the CLP regulation , according to TRGS 900 and TRGS 910 are assigned a workplace limit value and the permitted release according to TA Luft according to § 48 BImSchG is also limited, results for the for the invention usable binder according to Examples 1 and 7 a significant emission advantage. Surprisingly, the present invention also shows benefits in terms of casting quality. Casting defects caused by the molding material are a major problem in iron and steel casting. A frequently occurring casting defect in iron casting is the so-called leaf rib. It arises because the quartz sand used as the basic molding material undergoes a modification change due to heating at 573 °C due to casting. This change from so-called deep quartz to so-called braided quartz is accompanied by a sudden increase in the specific volume of the molding material. This volume change leads to cracks in the molding material, into which the melt penetrates. Leaf ribs form on the cast part. The effects of the so-called quartz crack can be reduced or intercepted by the plasticity of the binder, so that the molding material does not crack under the casting conditions. Cold box binders containing phenolic resin used to date are not able to prevent leaf vein formation. Molding materials with these binders have significant amounts of chemical additives added to reduce veining during casting.

Molding materials according to the invention show a significant improvement compared to the binders used hitherto with regard to the casting defect tendency of the resulting cast part. This was examined and documented in detail for the blade vein casting defect described above. For this purpose, so-called dome cores are manufactured using the cold-box process, which, due to their geometry, provoke the development of the blade vein casting defect. Depending on the quality of the resulting casting, the casting defect tendency of the molding materials used can be classified.

The compositions of the binders used in Examples 1 to 16 are shown below. All percentages [%] in this document are always to be understood as percentages by weight, unless a different definition is made in the explanatory text. The CAS registry number (CAS = Chemical Abstracts Service) is an international standard for naming chemical substances, whereby a unique CAS number exists for every known chemical substance.

Example 1: Example 2: Example 3:

Example 4: Example 5:

Example 6: Example 7:

Example 8: example 9

Example 10 Example 11

Example 12 Example 13

Example 14 Example 15

Example 16

Example A1 (not according to the invention)

Example A2 (not according to the invention)

The binders of the present invention are generally composed of a resin component consisting of a) polyester polyols, b) polycarbonate alcohols c) polyether polyols, d) short-chain crosslinkers and e) thinners, and also an isocyanate-containing hardener component.

In the examples presented, these components were varied in order to demonstrate the broad applicability of the general recipe. Thus, the proportions of the polyester polyols in the resin component were varied from 0% to 74%, the polycarbonate alcohols from 0% to 46% and the sum of the polyester polyols and polycarbonate alcohols from 42% to 74%.

On the part of the short-chain crosslinkers, dihydric aliphatic alcohols such as ethylene glycol or 1,3-propanediol and trihydric representatives such as trimethylolpropane have been used by way of example. However, water as a carbon-free substance or aromatic crosslinkers such as 2,2'-[1,3-phenylenebis(oxy)]bisethanol were also used. Combinations of these are also listed. Fatty acid methyl esters with C16 to C18 fatty acids and/or dibasic esters were mostly used as diluents, but tetraethyl orthosilicate and caprolactone were also used.

The isocyanate content of the hardener component varied between 75% and 89%. In Example 14, a hardener component was used in which 82 parts by weight of the MDI oligomer were reacted with 10 parts by weight of polyether polyol to give a prepolymer. Therefore, this hardener component already shows a slight development of the polymer network.

Not according to the invention, delimitation example A1 contains neither polyester polyols nor polycarbonate alcohols in the resin component. Here, the resin component consists exclusively of polyether polyols, short-chain crosslinkers, thinners and catalytically active additives. The hardener component consists of isocyanate and thinner. As in the examples of the invention are no phenolic components and contain formaldehyde.

Also not according to the invention, example A2 contains neither polyester polyols nor polycarbonate alcohols in the resin component. It is a classic example of the phenol formaldehyde resin based cold box binders currently used in foundries.

In the case of the resin component, the total equivalent weights given relate to the groups which are hydrogen-active towards isocyanate. They were calculated from the weight percentages and equivalent weights of the individual ingredients. The total equivalent weights, also referred to as average equivalent weights, are calculated, for example, from the percentage content of OH and/or SH and/or NH groups in the individual components, taking into account their mass fractions in the mixture.

On the part of the hardener component, the total equivalent weights given are based on the isocyanate groups present. These were determined experimentally according to ISO 14896:2009.

The viscosities of the components were determined using a Brookfield rotational viscometer in accordance with DIN EN ISO 2555:2018-09 in the unit mPas.

The binder test was based on method A described in VDG leaflet P73. The molding material mixture was produced in a paddle mixer from 100 parts by weight quartz sand H32 and 0.8 parts by weight resin component and hardener component or from 100 parts by weight chromite and each 0.4 parts by weight resin component and hardener component. Using the LUT core shooter from Multiserw, three test specimens each measuring 22.4 x 22.4 x 185 mm were injected into the introduced shaping core tool and then cured according to the process conditions below with a carrier gas-amine mixture.

The molding material strengths of the test specimens obtained in this way are determined as a function of time using the LRu-2e universal strength testing apparatus from Multiserw.

In the practice of every foundry, the strength of the cores when they are removed from the core tool and then when the cores are cast is relevant. These correspond to the immediate strength or final strength (24-hour value) of the test specimens. For the former, the warp-free handling and storability of the core removed from the core tool is important. Experience has shown that this is the case with a flexural strength of the test specimens of 100 N/cm ² . A flexural strength value of the test specimens of >280 N/cm ^{2 is} considered favorable as the ultimate strength after 24 hours. This ensures that cores hardened in the cold box process can be used from light metal castings to cast steel.

Test specimens were shot at a shooting pressure of 4 bar with the molding material mixtures, which were produced according to the above-mentioned method, and gassed with tertiary amine at 0.5 bar and then flushed with air. The amount of amine as well as the flushing time will vary according to the processes used:

Method 1: mass of DMEA per mass of molding material: 0.0045; rinsing time: 90 s; quartz sand H32;

Method 2: mass of DMEA per mass of molding material: 0.0045; rinsing time: 60 s; quartz sand H32;

Method 3: mass of DMEA per mass of molding material: 0.0045; rinsing time: 30 s; quartz sand H32; Method 4: mass of DMEA per mass of molding material: 0.0030; rinsing time: 90 s; quartz sand H32;

Method 5: mass of DMEA per mass of molding material: 0.0060; rinsing time: 120 s; quartz sand H32;

Method 6: mass of DMEA per mass of molding material: 0.0090; rinsing time: 300 s; quartz sand H32;

Process 7: mass of DMPA per mass of mold material: 0.0045; rinsing time: 90 s; quartz sand H32;

Method 8: mass of DMEA per mass of mold material: 0.0045; rinsing time: 90 s; chrome it.

For Examples 1 to 16, molded material test specimens could be cured in accordance with methods 1 to 7 using amounts of amine customary in the cold box method. A suitability of the molding materials according to the invention for use in the cold box process was thus demonstrated.

The situation is different in example A1, which is not according to the invention. Despite accelerating additives and a slightly increased amount of amine gas as well as a longer rinsing time, the associated molding material test specimens could not be cured. Test specimens could only be obtained by further increasing the amine mass used per molding material mass to 0.009 and the gassing time to 300 seconds. However, these showed neither sufficient removal strengths nor final strengths. Molded materials with the non-inventive binder Example A1 are therefore not suitable for use in the cold box process because the cycle times and amounts of amine are well outside the range required in the cold box process.

It is clear from this that the use of a polyurethane-based binder, the fluff of which is made up of aliphatic, phenol- and formaldehyde-free components, requires a polyester polyol and/or a polycarbonate alcohol in the cold box process. In addition, it is possible to add a large number of polyether polyols, short-chain crosslinkers, to the Flarz component or add diluents and get process-ready performances of the resulting binders. The examples also show that variations in the amine gas and in the process parameters lead to comparable results.

Table 1 shows the flexural strength of the standard test specimens in the cold box method.

Table 1

* Lab-Jet gassing unit, Lüber-GmbH

The dome cores for assessing the inclination of the leaf veins were produced by mixing 100 parts by weight of quartz sand H32 and 0.8 parts by weight each of resin and hardener component in a paddle mixer and then introducing the molding material mixture into the dome core mould. The dome core corresponds to a cylinder (diameter = 48 mm, height = 25 mm) with an attached hemisphere. Curing took place by gassing with amine according to process 1 with the gassing device Lab-Jet from Lüber-GmbH. After gluing the dome cores into a corresponding mold, they were cast with cast iron at a melt temperature of 1350 °C. A large number of non-standard methods are known for assessing the inclination of leaf veins. A school grading system is used here, which takes into account the number of leaf veins and their width and height. With a rating of 1, no veins may appear, with a rating of 2 only slight approaches to veining, with a rating of 3, a few veins or a slight one Expression, with grade 4 a medium number or clear development of the leaf veins, with grade 5 many or very pronounced leaf veins and with grade 6 very many or very pronounced leaf veins. In the case of the binders used according to the invention in Examples 1, 2 and 14, there were only weakly pronounced deposits of leaf veins (rating 2). In the case of comparative example A2 (phenolic resin binder CB), on the other hand, a significantly higher number and greater expression and branching of leaf veins were observed (rating 4).

List of abbreviations used in the tables (without chemical symbols)

CMR CMR substances have one or more of the following properties: C = carcinogenic (carcinogenic), M = mutagenic (mutagenic), R = toxic to reproduction

(toxic for reproduction)

DABCO diazabicyclo[2.2.2]octane

DEMA diethylmethylamine

DMEA N,N-dimethylethylamine

DMIPA dimethylisopropylamine

DMPA N,N-dimethylpropylamine

H32 Halterner quartz sand type (grain size range)

MDI diphenylmethane diisocyanate

MG molecular weight in [g/mol]

PEG polyethylene glycol

Claims

patent claims

1. Molding material for the production of cores in the cold box process, comprising the following components:

- A two-component, phenol and phenol derivative-free binder based on polyurethane containing a resin component comprising one or more branched aliphatic or aromatic polyester polyols, built up from branched aliphatic or aromatic diol or triol starters with one or more side chains and substituted or unsubstituted aliphatic and/or aromatic di- and/or tri-carboxylic acids or their anhydrides and/or one or more polycarbonate alcohols with equivalent weights of 250 to 4000 g/val and hydroxy functionalities of 2 to 4 as hydrogen-active compounds with respect to isocyanates, wherein the or the branched polyester polyols and/or polycarbonate alcohols of the resin component of the binder have a proportion in the range from 35 to 100% by weight of the resin component, and a hardener component comprising one or more polyisocyanates,

>- and one or more refractory pourable fillers.

2. Molding material according to claim 1, characterized in that the resin component of the two-component binder contains, in relation to isocyanate, hydrogen-active individual compounds, the resin component having an average functionality of 1.8 to 4.0 with respect to the totality of these hydrogen-active individual compounds, and as Additive(s) one or more thinners and optionally comprises one or more catalysts affecting the polymerization and the hardener component comprises one or more isocyanates which have at least functionality 2, and as an additive one or more diluents.

3. Molding material according to Claim 1 or 2, characterized in that the Flarzkom component of the two-component binder contains further individual compounds which are hydrogen-active in relation to isocyanate and which are selected from one or more substance classes, comprising polyether alcohols, polyester polyols, polycarbonate alcohols, polyether polyester alcohols, polythiols, aminopolyether alcohols, difunctional and higher functional alcohols, amines and carbamide compounds with an OH, SH and NFI functionality of 1.5 to 8 and equivalent weights of 9 to 2000 g/val of the hydrogen-active individual compounds.

4. Molding material according to one of claims 1 to 3, characterized in that side chains of a branched polyester polyol of the molding material are selected from aliphatics, aromatics, aldehydes, ketones, carboxylic acid esters, ethers, amines, alkyl halides, nitriles, nitrogen, oxygen and sulfur Fleterocycles and carboxylic acid amides.

5. Molding material according to one of claims 1 to 4, characterized in that the or the branched polyester polyols and/or polycarbonate alcohols of the fluff component of the binder have a proportion in the range of 40 to 80% by weight of the fluff component.

6. Molding material according to one of Claims 1 to 5, characterized in that the individual compounds of the Flarz component of the gas-hardening mold material are combined in such a way that an average hydrogen functionality of 2.2 to 3.5 results.

7. Molding material according to one of claims 1 to 6, characterized in that the isocyanates of the flärter component of the gas-curing molding material are oligomers or polymeric derivatives of the basic type of 2,4'- and 4,4'-diphenylmethane diisocyanate and/or oligomeric or polymeric derivatives of the 2,4'- and 4,4'-dicyclohexylmethane diisocyanate type and/or oligomeric or polymeric derivatives of hexamethylene diisocyanate with optionally fully or partially blocked isocyanate groups and/or isophorone diisocyanate and/or its derivatives.

8. Molding material according to one of Claims 1 to 7, characterized in that the isocyanates of the hardener component consist entirely or partially of pre-crosslinked reaction products with a stoichiometric deficiency of hydrogen-active compounds, the pre-crosslinking being brought about by the reaction with difunctional or polyfunctional polyols and a residual content of free isocyanate groups in the range from 15 to 30%, preferably from 18 to 25%.

9. Molding material according to one of claims 1 to 8, characterized in that the isocyanate content of the hardener component is selected in relation to the hydrogen-active compounds of the resin component such that free NCO groups of the hardener component and OH and /or NH and/or SH groups of the resin component are present in a molar ratio of 0.8 to 1.2.

10. Molding material according to one of claims 1 to 9, characterized in that the resin component of the binder is 45 to 100% by weight, preferably 70 to 90% by weight, of hydrogen-active compounds and the hardener component of the binder has 60 to 100% by weight, preferably 75 to 90% by weight, of polyisocyanates.

11. Molding material according to one of Claims 1 to 10, characterized in that the resin component of the binder can contain tertiary amines and/or organometallic compounds which accelerate the polyurethane reaction as catalysts.

12. Molding material according to one of claims 1 to 11, characterized in that the resin and hardener components of the binder have one or more diluents, these being selected from the substance classes fatty acid esters based on renewable raw materials, synthetic mono-, di- and Tricarboxylic acid esters, organosilicates, sulfonic acid esters, paraffins, phosphoric acid esters, cyclic and non-cyclic carbonates and non-hydroxy-terminated polyethers.

13. Molding material according to one of claims 1 to 12, characterized in that as the filler or fillers quartz sand, chromite, zircon sand, olivine sand, R-sand, magnesia, alkali metal and alkaline earth metal halides, aluminum silicates such as J-sand and kerphalite , synthetic sands such as cerabeads, chamotte, M-sand, Alodur, bauxite sand and silicon carbide, expanded and foam glass, fly ash and other special sands are used and have an average grain size of 0.1 to 0.9 mm.

14. Molding material according to one of claims 1 to 13, characterized in that the gas-hardening molding material is mixed from one or more refractory, pourable fillers at 96.0 to 99.7% and a binder at 0.3 to 4.0%.

15. A method for curing a molding material according to any one of claims 1 to 14, wherein

>- the molding material is brought from a storage vessel into a core tool and compressed by applying compressed air at a pressure of 0.5 to 10.0 bar,

>- is then cured in the core tool by a carrier gas-amine mixture, which preferably contains volatile, tertiary amines, the temperature of the carrier gas-amine mixture preferably being in the range from 15° C. to 100° C., and

>- After another flushing process with air, the hardened molded part is removed from the core tool or ejected.