EP3551360B1 - Alkaline resol binders having improved flowability - Google Patents

Description

introduction

The invention relates to molding mixtures for the production of molds, cores or feeders for metal casting, comprising at least one refractory base molding material, a binder based on an alkaline resol resin and at least one sugar surfactant. The invention also relates to a method for producing molds and cores using the molding material mixtures and to molds, cores and feeders produced by this method.

Background of the invention

Casting molds are essentially composed of molds or molds and cores, which represent the negative shape of the casting to be produced. These molds and cores generally consist of a refractory basic molding material, for example quartz sand, and a suitable binding agent which gives the casting mold sufficient mechanical strength after it has been removed from the mold. The refractory basic molding material is preferably in free-flowing form so that, after mixing with the binder, it can be filled into a suitable hollow mold, compacted and then cured. After curing, the binding agent ensures that the particles of the basic mold material are held together firmly so that the casting mold has the required mechanical stability.

During casting, molds form the outer wall for the casting, cores are used to form cavities within the casting. It is not absolutely necessary that the molds and cores are made of the same material. In chill casting, for example, the external shaping of the cast pieces is done with the help of permanent metallic molds. A combination of molds and cores that have been produced from differently composed molding material mixtures and using different processes is also possible. Feeders are cavities in the casting mold that are filled with liquid metal together with the casting during casting. The feeder keeps the metal in it liquid longer and can thus compensate for a volume deficit in the solidification phase of the casting.

If, for the sake of simplicity, only cores are referred to below, the statements also apply to the same extent to molds and feeders that are based on the same molding material mixture and were manufactured using the same process.

To produce cores, organic, inorganic and mixed organic / inorganic binders (hybrid systems) can be used, the hardening of which can take place in each case by cold or hot processes. Cold processes are those processes that are carried out essentially without heating the mold used to manufacture the core, usually at room temperature or at a temperature caused by any reaction. The hardening takes place, for example, in that a gas is passed through the molding material mixture to be hardened, thereby triggering a chemical reaction. In hot processes, the molding material mixture is e.g. heated by the heated mold to a sufficiently high temperature to drive off the solvent contained in the binder and / or to initiate a chemical reaction by which the binder is hardened.

The use of alkaline phenolic resins as binders for casting molds is known per se and these are for example in the EP 0323096 B2 and in the EP 1228128 B1 disclosed. These are alkaline resol resins that can be hardened by introducing CO ₂ . Essential components of the binders described in the patents mentioned are oxyanions, e.g. the borate ion ( EP 032096 B2 ) or the combination of borate and aluminate ions ( EP 1228128 B1 ).

Object of the invention

Molding mixtures with alkaline resole resins often show poor flowability. This is noticeable in that fine core areas are incompletely depicted, the cores are not compactly compressed and thus lose strength or the molding material mixture in the shooting head stalls and does not continue to flow. In the latter case, a cavity then forms and the sand can only be pushed in by mechanical tamping. Various proposals have already been made to address this problem.

US 5077323 describes ester-hardening alkaline resol resins (= Alphaset process), the flowability of which is improved by adding fatty acids, fatty alcohols, fatty amines, fatty acid amides or fatty acid alkanolamides. US 5376696 or the WO 92/01016 A1 describe sand mixtures for ester-hardening alkaline resole resins, in which a surfactant solution is added to the sand mixture to improve the flowability. EP 0399636 A2 describes ester-hardening alkaline resole resins which contain a fluorosurfactant, which can have an anionic, cationic, amphoteric or nonionic character. It improves the flowability of the molding material mixture. JP 3 250915 B2 discloses molding material mixtures with alkaline resols and various surfactants, including sugar esters. DE 10 2012 104934 A1 discloses waterglass-based molding material mixtures with various surfactants, including polyglycosides based on fatty alcohol. Also DE 10 2007 051850 A1 discloses waterglass-based molding material mixtures with various surfactants, including carbohydrates etherified with alkyl groups.

However, there is still a need to further develop molding mixtures containing alkaline resole resins such that they have improved flowability. In this way, cores with more complex geometries could also be produced or, in the case of massive, simple cores, the binder content could be reduced, which on the one hand would increase the efficiency of the process and on the other hand would reduce the amount of emissions occurring during casting. The object of the invention is therefore to improve the flowability of the basic molding material impregnated with an alkaline resol.

Summary of the invention

This object is achieved by molding material mixtures with the features of claim 1. Claim 13 describes a method for producing a core, feeder or a mold, and claim 14 describes a mold, feeder or a core. Advantageous further developments are the subject of the dependent claims and are described below.

Surprisingly, it has been found that the addition of sugar surfactants significantly improves the flowability of mixtures of alkaline resole resin and refractory basic molding materials. This is surprising insofar as the surface tension of an alkaline resole resin is only slightly reduced by a sugar surfactant. The sugar surfactant i used according to the invention is an alkyl polyglycoside and is contained in the alkaline resole resin component or it is added pure or diluted as the second component directly to the molding material mixture before or during mixing.

1. a) einen feuerfesten Formgrundstoff;
2. b) ein alkalisches Resolharz ; in einer Menge von 0,8 bis 10 Gew.%, bezogen auf den Feststoffgehalt des alkalischen Resols und relativ zum Gewicht des feuerfesten Formgrundstoffs, als Bindemittel welches mittels CO₂; Methylformiat (als Aerosol, gasförmig oder flüssig) oder einem anderen flüssigen (bei Raumtemperatur = 25°C) Ester härtbar ist; und
3. c) ein Zuckertensid, nämlich ein Alkylpolygycosid, welches auch als Zuckertensidlösung zugegeben
   werden kann.

The molding material mixture according to the invention thus comprises at least

1. a) a refractory molding base material;
2. b) an alkaline resole resin; In an amount of 0.8 to 10% by weight, based on the solids content of the alkaline resole and relative to the weight of the refractory base molding material, as a binder which by means of CO ₂ ; Methyl formate (as aerosol, gaseous or liquid) or another liquid (at room temperature = 25 ° C) ester is curable; and
3. c) a sugar surfactant, namely an alkyl polygycoside, which is also added as a sugar surfactant solution
   can be.

• Vermischen von alkalischem Resolharz, Zuckertensid und feuerfestem Formgrundstoff zum Erhalt einer Formstoffmischung;
• Einbringen der Formstoffmischung in ein Formwerkzeug;
• Härten der Formstoffmischung mittels CO₂; Methylformiat (als Aerosol, gasförmig oder flüssig) oder einem anderen flüssigen Ester; und
• Entnahme des gehärteten Kerns, des Speisers oder der Form aus dem Formwerkzeug.

The invention also relates to a method for producing a core comprising the following steps:

• Mixing of alkaline resole resin, sugar surfactant and fireproof molding base material to obtain a molding material mixture;
• Introducing the molding material mixture into a molding tool;
• Hardening of the molding material mixture by means of CO ₂ ; Methyl formate (as an aerosol, gaseous or liquid) or another liquid ester; and
• Removal of the hardened core, the feeder or the mold from the mold.

Detailed description of the invention

The binders are alkaline resole resins. The resoles are produced by the condensation of phenolic compounds and aldehyde compounds in the presence of a basic catalyst such as ammonium hydroxide or an alkali metal hydroxide. Alkali metal hydroxide catalysts are preferably used.

The resoles are used in a concentration of 0.8% by weight to 10% by weight, preferably from about 1% by weight to about 5% by weight and particularly preferably from about 1% by weight to about 4% by weight. % used, each based on the solids content of the resol (according to DIN EN ISO 3251) and the basic molding material. The concentration of binder within the casting mold can vary.

Resoles in the sense of the present invention are aromatics linked to one another via methylene groups (-CH ₂ -) groups and / or via ether bridges (in particular -CH ₂ -O-CH ₂ -), each of which has at least one -OH group (phenol compound) .

Suitable phenolic compounds are phenols, substituted phenols, e.g. Cresols or nonylphenol, 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), cashew nut shell oil, i.e. a mixture of cardanol and cardol, or 1,4-dihydroxybenzene (hydroquinone) or phenolic compounds such as e.g. Bisphenol A.

Examples of suitable aldehyde compounds are formaldehyde, paraformaldehyde and glyoxal and mixtures thereof. Formaldehyde or mixtures containing predominantly formaldehyde (based on the molar amount of the aldehydes) are particularly preferred.

The molar ratio of phenol compound to aldehyde compound is preferably between 1.05: 1.2 to 1.05: 2.6, particularly preferably between 1.1: 1.3 to 1.1: 2.5.

Resoles are preferred in which adjacent hydroxy aromatics are each linked at the ortho and / or para position (relative to the hydroxy group of the built-in phenol / aromatics) via the methylene bridges and / or the ether bridges, i.e. the majority of the links are para and / or ortho.

Examples of suitable oxyanions in the binder composition for the resole / CO ₂ process include borate, stannate and aluminate ions. Aluminate and borate ions are preferred. The oxyanion can be added to the binder composition for the resol / CO ₂ process by mixing in sodium tetraborate times x H ₂ O, potassium tetraborate times x H ₂ O, sodium metaborate, sodium pentaborate, sodium stannate trihydrate, sodium aluminate, potassium aluminate, aluminum hydroxide, aluminum oxide or ammonium oxyanion salt such as ammonium borate. Borate ions can also be introduced by adding boric acid or boron oxide.

The molar ratio of oxyanions (expressed as boron and / or aluminum and / or tin) to phenol group is preferably in the range from 0.1: 1 to 1: 1. When the oxyanion is borate, the molar ratio of boron to phenol is particularly preferably in the range 0.1: 1 to 0.5: 1.

It is also possible to introduce organic aluminum, boron or tin compounds. Furthermore, the oxyanions can also be obtained by introducing organic boron, aluminum and tin compounds such as aluminum alcoholates of the formula Al (OR) ₃ , where R can independently be a saturated or unsaturated, branched or unbranched hydrocarbon radical with 1 to 10 carbon atoms. A solution of a boron compound such as boric acid or boric acid ester in alkali is suitable as a solution of a boron-containing oxyanion.

The solution of a base in water, which is also used for mixing with the resole resin, serves as the lye.

Organic bases such as e.g. Amines or ammonium compounds as well as inorganic bases such as e.g. Alkali metal hydroxides can be used. Alkali hydroxides such as e.g. Sodium hydroxide and potassium hydroxide are used. The molar ratio of hydroxide ions to the phenol group in the binder system is preferably 0.5: 1 to 3: 1, preferably 1.0: 1 to 2.5: 1. It is not necessary that the total amount of base is already at the beginning of the Condensation is added; The addition is usually carried out in two or more sub-steps, some of which can also only be added at the end of the manufacturing process. Mixtures of basic catalysts can also be used.

The production of alkaline resoles is for example in the EP 0323096 B2 and EP 1228128 B1 disclosed. Further binders based on resol are for example in the US 4426467 and the US 4474904 described.

In addition to the constituents already mentioned, the resole contains water, preferably in an amount of 15% by weight to 50% by weight, based on the binder. Finally, components of the binding agent are resol, water, alkalis and oxyanion. On the one hand, the water can come from aqueous solutions that are used in the production of binders, on the other hand, it can also be added separately to the binder or come as condensation water from the resol condensation.

In addition to its function as a solvent, water also serves, for example, to give the binder an application-appropriate viscosity (25 ° C.) of 5 to 1200 mPas, preferably from 10 to 1100 mPas and particularly preferably from 10 to 950 mPas. The viscosity is determined with the aid of a Brookfield rotary viscometer, _" Small Sample" method, spindle no. 21 at 100 rpm and 25 ° C. The alkaline resole preferably has a pH value (at 25 ° C.) greater than 12.

Furthermore, up to approx. 50% by weight of additives such as Alcohols, glycols, and silanes may be added. With the help of these additives, for example, the wettability of the molding material by the binder and its adhesion to the molding material can be increased, which in turn can lead to improved strengths and increased moisture resistance.

The addition of silanes has a particularly positive effect in this regard, e.g. gamma-aminopropyltriethoxysilane or gamma-glycidoxypropyltrimethoxysilane, in concentrations of about 0.1% by weight to about 4.0% by weight, preferably from about 0.2% by weight to about 3.0% by weight and particularly preferably from about 0.3% by weight to about 2.5% by weight, each based on the weight of the molding material composition.

The esters suitable for hardening the resols (alphaset process) are, for example, from those skilled in the art US 4426467 , US 4474904 and US 5405881 known. They include lactones, organic carbonates and esters of C1 to C10 mono- and polycarboxylic acids with C1 to C10 mono- and polyalcohols. Preferred but non-limiting examples of these compounds are gamma-butyrolactone, propylene carbonate, ethylene glycol diacetate, mono-, di- and triacetin and the dimethyl esters of succinic acid, glutaric acid and adipic acid, including their mixture known under the name DBE. Due to the different saponification rates of the individual esters, the rate of hardening of the resols varies depending on the ester used, which can also influence the strengths. The desired curing time can be varied within wide limits by mixing two or more esters.

Carbon dioxide or methyl formate as an aerosol or heated as a gas is also suitable for hardening the resols.

Sugar surfactants are nonionic surfactants in which sugars form the hydrophilic part of the surfactant molecule. Fatty alcohol or fatty acid residues act as hydrophobic components. Carbohydrates used are, for example, glucose, methylglucose, fructose, methylfructose, lactose, ribose, sucrose, xylenose, xylitol, mannose, mannitol, isosorbitol and sorbitol.

The sugar building blocks can be used as monomers or up to a degree of polymerization of 30. The sugar building blocks can be alpha or beta 1,4 glycosidically linked. The hydrophilic component is preferably formed by linking glucose, sucrose, fructose, isosorbitol and / or sorbitol; sucrose and / or glucose is particularly preferred.

Fatty acids can be esterified or fatty alcohols and / or fatty alcohol ethoxylates, fatty alcohol propoxylates and / or fatty alcohol ethoxylates / fatty alcohol propoxylates, the chain length is between C ₆ and C ₃₂ , in particular C ₈ and C ₂₂ , and can be branched or straight-chain and saturated to the free hydroxyl groups or be unsaturated. Both the sugar and the fat building blocks can be mixed together. According to the invention, alkyl polyglycosides (APG), in particular alkyl polyglucosides, are used which have the following exemplary structure.

m stands on average for 1 to 30, preferably on average from 2 to 25 and particularly preferably on average from 2 to 10.n stands for a saturated or unsaturated, straight-chain or branched alkyl radical with an average of 5 to 31 carbon atoms and particularly preferably 7 to 21 carbon atoms.

Alkyl polyglycosides are produced on an industrial scale and sold by BASF under the trade names Plantacare or Glucopon.

The sugar surfactants according to the invention are preferably added to the resole resin in a concentration of 0.05 to 5.0% by weight. Preferably in a range from 0.05 to 3.0% by weight and particularly preferably from 0.05 to 2.0% by weight, relative to the binder. In a further embodiment, the sugar surfactants according to the invention can be added directly to the molding material mixture. This can be done as a pure substance or dissolved in a carrier medium (e.g. water). Based on the finished molding material mixture, 0.005 to 0.5% by weight, preferably 0.01 to 0.3% by weight, of sugar surfactant are added.

The sugar surfactants used preferably have an HLB value between 11 and 16 (HLB stands for hydrophilic-lipophilic balance).

Conventional materials for the production of casting molds can be used as the refractory basic molding material (hereinafter abbreviated to basic molding material (s)). For example, quartz sand, zircon sand or chrome ore sand, olivine, vermiculite, bauxite and chamotte or mixtures thereof are suitable. If there are no technological reasons to the contrary, quartz sand is preferred for economic reasons.

It is not necessary to only use new sand. In order to conserve resources and avoid landfill costs, it is even advantageous to use the highest possible proportion of regenerated used sand. Regenerated materials obtained by washing and subsequent drying are particularly suitable. Regenerated materials obtained by thermo-mechanical or purely mechanical treatment can also be used.

The mean diameter of the basic mold 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 e.g. determine by sieving according to DIN ISO 3310.

Artificial molding materials can also be used as molding base materials, in particular as an additive to the above molding base materials, but also as exclusive molding base material, such as glass beads, glass granulate, the spherical ceramic molding base materials known under the name "Cerabeads" or "Carboaccucast" or aluminum silicate microbeads (so-called hollow spheres). Microspheres). Such hollow aluminum silicate microspheres are marketed, for example, by Omega Minerals Germany GmbH, Norderstedt, under the name "Omega-Spheres". Corresponding products are also available from PQ Corporation (USA) under the name "Extendospheres".

It is also possible to add amorphous silicon dioxide to the basic molding material. This increases the strength. This is among other things in the DE 102014106178 disclosed.

When producing a molding material mixture, the procedure is generally that the refractory molding base material is initially introduced and then the binder and the sugar surfactant are added together or one after the other with stirring. It is of course also possible to add all or some of the components first and then to stir and / or during this. The mixture is stirred until a uniform distribution of the binder and the sugar surfactant with the basic molding material is guaranteed.

The molding material mixture is then brought into the desired shape. The usual methods are used for shaping. For example, the molding material mixture can be shot into the tool by means of a core shooting machine with the aid of compressed air. Another possibility is to allow the molding material mixture to trickle freely from the mixer into the molding tool and to compress it there by shaking, tamping or pressing.

The preferred core production process is the resole / CO ₂ process. However, this does not exclude gassing with lower alkyl esters, known under the name Betaset processes such as C1 to C3 alkyl formates, in particular methyl formate, and curing by means of liquid esters, known under the name Alphaset process.

Curing takes place in that CO ₂ , a CO ₂ / gas mixture (e.g. with air), a gas mixture (e.g. air) or gaseous methyl formate (in the Betaset process) one after the other (as e.g. in detail in the DE 102012103705.1 described) is passed through the mold or through the molding material mixture contained therein.

The gas stream has a temperature between 0 ° C and 140 ° C, preferably from 5 ° C to 120 ° C and particularly preferably from 6 ° C to 110 ° C.

Experimental part Components used:

NOVANOL 165 - alkaline resol / CO ₂ binder, supplier to ASK-Chemicals GmbH
AVENOL F 633 - alkaline betaset binder, supplier ASK-Chemicals GmbH
Quartz sand H 32 - supplier Quarzwerke GmbH
Oleic acid = technical oleic acid
Capstone FS 35 = 25% aqueous solution of a nonionic fluorosurfactant, manufacturer: Chemour
Plantacare 2000 UP: 50% aqueous alkyl polyglucoside solution with C ₈ -C ₁₆ fatty alcohol chains, manufacturer: BASF SE
All data in% by weight.

Determination of surface tension

Each x% of the substances listed in the table below were added individually to NOVANOL 165 and dissolved clearly. 200 g of the homogeneous, clear and air bubble-free mixture was placed in a PTFE beaker and the surface tension (in mN / mm) was measured at room temperature. A Krüss Force Tensiometer 100 (from Krüss) was used for this. The plate method (roughened platinum plate) according to Wilhelmy was used as a double determination. If a vertically suspended plate touches a liquid surface or interface, a force F acts on this plate, which correlates with the surface tension. <i> Table 1 </i> # additive mN / mm comment A0 without 34.5 comparison A1 0.25% oleic acid * 31.2 according to U.S. 5,077,323 A2 0.50% oleic acid 30.3 A3 0.75% oleic acid 30.2 A4 1.0% oleic acid 29.9 A5 0.25% Capstone FS 35 30.6 according to EP 0 399 636 A6 0.50% Capstone FS 35 28.1 A7 0.75% Capstone FS 35 26.1 A 8 1.0% Capstone FS 35 * 25.1 B1 0.25% Plantacare 2000 UP 34.3 according to the invention B2 0.50% Plantacare 2000 UP * 33.7 B3 0.75% Plantacare 2000 UP 32.8 B4 1.0% Plantacare 2000 UP 32.3 % =% By weight relative to the binder

Table 1 shows the surface tensions found (in mN / mm) at room temperature, which were obtained by adding the surfactants. If one looks at the surface tension (comparison of the same amount of active substance, identifier with “*”), it is surprisingly noticeable that the APG type sugar surfactants according to the invention reduce the surface tension by only 2% (zero example for B2).

Compared to the prior art according to U.S. 5,077,323 the oleic acid reduces the surface tension by 10% (zero example for A1), according to EP 0399 636 a reduction of 27% is even achieved (zero example for A8). Water with a value of 68.8 mN / mm was used as a reference.

Determination of strength in N / cm ² - Resole CO ₂ method

A sand mixture of quartz sand H 32, plus 3.0% NOVANOL 165 (without or with the listed substances) was mixed homogeneously in a Hobart mixer for 2 minutes. This sand mixture was transferred to a core shooting machine, model Laempe L 1 (opening at the sand outlet of the shooting head reduced to 5mm) and was placed in a four core box (GF bar 220mm x 22.4mm x 22.4 mm) with a shooting pressure of 2 bar using compressed air and a shooting time of 1 sec into the mold. The sand was hardened by means of CO ₂ gas (2 liters / min for 30 seconds). After three shots, without the 1 liter shooting head being filled, the sand mixture was visually assessed to determine whether the sand was flowing.

The flexural strengths were broken using a flexure tester from Multiserw after the specified time (mean values from four determinations). <i> Table 2 </i> # additive Strength in N / cm ² Sand river after 3 shots 60 sec immediately 24h RT 24h RT 98% A0 without 81 139 108 stops A1 0.25% oleic acid * 85 144 104 stops A2 0.50% oleic acid 81 146 101 slips A3 0.75% oleic acid 80 137 95 slips A4 1.0% oleic acid 76 131 90 slips A5 0.25% Capstone FS 35 80 133 110 stops A6 0.50% Capstone FS 35 77 130 111 stops A7 0.75% Capstone FS 35 78 127 105 stops A8 1.0% Capstone FS 35 * 79 129 106 stops B1 0.25% Plantacare 2000 UP 84 155 117 slips B2 0.50% Plantacare 2000 UP * 83 145 113 slips B3 0.75% Plantacare 2000 UP 83 139 106 slips B4 1.0% Plantacare 2000 UP 82 136 101 slips

Table 2 shows that the flexural strengths measured immediately with the Plantacare 2000 UP according to the invention (example B1-B4) remain constant with increasing concentration, while they decrease with increasing oleic acid content (example A1-A4). In the column "Sand flow after 3 shots", the remaining sand in the firing head was assessed visually. "Stuck" means that a cavity has formed above the shooting openings in which the sand does not slide. "Slips" means that the cavity does not exist and has been closed by sliding sand. This means that shooting can continue without shaking. This effect is surprising for the sugar surfactants according to the invention (here Plantacare 2000 UP), since it encourages the sand to slide down.

Determination of strength in N / cm ² - Betaset method

A sand mixture of quartz sand H 31, plus 2.3% AVENOL F 633 (without or with the listed substances) was mixed homogeneously for 2 minutes in a Hobart mixer. This sand mixture was transferred to a core shooter, model Roeper H 1 (opening at the sand outlet of the shooting head 10 mm) and was in a two core box (GF bar 220mm x 22.4mm x 22.4 mm) with a shooting pressure of 3 bar by means of compressed air and brought into the mold with a shooting time of 1 sec. The sand was hardened by means of methyl formate gas at 60 ° C. (2.0 ml of liquid methyl formate, for 20 seconds, 2 bar flushing pressure). The flexural strengths were determined using a flexure tester from Multiserw after the specified time (mean values from four determinations). Table 3 # Additive Strength in N / cm ² Core weight 15 sec immediately 24h RT 24h RT 98% [G] A9 without 125 155 175 118 A10 0.50% oleic acid 80 225 210 123 A11 0.50% Capstone FS 35 130 255 180 125 B5 0.50% Plantacare 2000 UP 145 285 220 129 A9 = comparison, A10 according to US 5077323 ; A11 according to EP 0399636 : B5 according to the invention

It can be seen from Table 3 that the addition of the Plantacare 2000 UP according to the invention achieved the highest strengths in N / cm ² and the highest packing density (indicated by the core weight).

Claims (14)

1. A molding material mixture comprising at least one refractory molding base material, an alkaline resol and an alkyl polyglycoside, wherein the alkaline resol is comprised in the molding material mixture in an amount of 0.8 to 10% by weight, based on the solids content of the alkaline resol and in relation to the weight of the refractory molding base material.
2. The molding material mixture according to claim 1, wherein the alkyl polyglycoside has a degree of polymerization of 1 to 30, in particular 2 to 10, and a number of C atoms of the alcohol residue of 6 to 32.
3. The molding material mixture according to claim 1, wherein the alkyl polyglycoside has a degree of polymerization of 1 to 30, in particular 2 to 10, and a number of C atoms of the alcohol residue of 8 to 22.
4. The molding material mixture according to at least one of the preceding claims, wherein the alkyl polyglycoside has a HLB value of 11 to 16.
5. The molding material mixture according to at least one of the preceding claims, wherein the alkyl polyglycoside is comprised from 0.05 to 5.0% by weight, preferably 0.05 to 3.0% by weight and particularly preferably 0.05 to 2.0% by weight, in the molding material mixture, based on the solids content of the alkaline resol.
6. The molding material mixture according to at least one of the preceding claims, wherein the alkyl polyglycoside is comprised from 0.005 to 0.5% by weight, preferably 0.01 to 0.3% by weight, in the molding material mixture, based on the molding material mixture.
7. The molding material mixture according to at least one of the preceding claims, wherein the alkaline resol is comprised in an amount of 1 to 5% by weight in the molding material mixture, based on the solids content of the alkaline resol and in relation to the weight of the refractory molding base material.
8. The molding material mixture according to at least one of the preceding claims, wherein the alkaline resol comprises oxyanions, preferably aluminium-oxo compounds and/or boron-oxo compounds.
9. The molding material mixture according to at least one of the preceding claims, wherein the resols are used in the form of an aqueous alkaline solution, preferably having a solids content of 15 to 50% by weight, and a pH value of greater than 12.
10. The molding material mixture according to at least one of the preceding claims, wherein the refractory molding base material comprises silica sand, zircon sand or chrome ore sand, olivine, vermiculite, bauxite, chamotte, glass beads, glass granules, aluminum silicate micro hollow spheres and mixtures thereof, and preferably comprises more than 50% by weight of silica sand, based on the refractory molding base material.
11. The molding material mixture according to at least one of the preceding claims, wherein more than 80% by weight, preferably more than or equal to 90% by weight, and particularly preferably more than or equal to 95% by weight, of the molding material mixture is refractory molding base material.
12. The molding material mixture according to at least one of the preceding claims, wherein the refractory molding base material has mean particle diameters of 100 µm to 600 µm, preferably between 120 µm and 550 µm, as determined by sieve analysis.
13. A method for producing a core, a feeder or a mold comprising the following steps:

    introducing the molding material mixture according to at least one of the preceding claims, optionally containing further components, into a mold tool;

    curing the molding material mixture in the mold tool with CO₂, methyl formate or another ester that is liquid at 25°C, preferably with CO₂; and

    removing the cured core, feeder or the mold from the molding tool.
14. A mold, feeder or core manufacturable by the method according to claim 13 for metal casting, in particular iron or aluminum casting.