EP1137500B9 - Binder system for producing polyurethane-based cores and moulds - Google Patents

Abstract

The present invention relates to a binder system that comprises a phenolic-resin component and a polyisocyanate component. This system is characterised in that the phenolic-resin component includes an alkoxy-modified phenolic resin, wherein less than 25 mole % of the phenolic hydroxy groups are etherified with a primary or secondary aliphatic alcohol comprising between 1 and 10 carbon atoms.

Description

The present invention relates to a binder system for the production of Cores and molds based on polyurethane.

The named "cold box method" or "Ashland method" has become known in the foundry industry a top position conquered. To bind the sand are in this Method two-component polyurethane systems used. The Component 1 consists of the solution of a polyol that at least contains two OH groups per molecule. Component 2 is the solution of a Polyisocyanate with at least two NCO groups per molecule. The Curing of the binder system is carried out using basic Catalysts. Liquid bases can be added to the binder system before Shaping be added to the two components for the reaction to bring (US-A-3,676,392). Another possibility is according to US-A-3,409,579 therein, gaseous tertiary amines after shaping by the To pass molding material / binder system mixture.

In the two patents mentioned, phenolic resins are used as polyols used by condensation of phenol with aldehydes, preferably Formaldehyde, in the liquid phase at temperatures up to approx. 130 ° C in Presence of catalytic amounts of metal ions can be obtained. In US-A-3,485,797 the preparation of such phenolic resins is described in detail. Besides unsubstituted phenol, substituted phenols, preferably o-cresol and p-nonylphenol (e.g., EP-A-183,782). When further reaction component can according to EP-B-0177771 in the Production of phenolic resins aliphatic monoalcohols with one to eight Carbon atoms are used. By the alkoxylation should the Binder systems have increased thermal stability. When Solvents for the phenolic component are predominantly mixtures from high boiling point polar solvents (e.g., esters and ketones) and high-boiling aromatic hydrocarbons used. The On the other hand, polyisocyanates are preferred in high-boiling aromatic Hydrocarbons dissolved. In European Patent Application EP-A-0 771 599 formulations are described in which by use of fatty acid methyl esters wholly or at least largely aromatic Solvent is omitted. The fatty acid methyl esters are included either as a sole solvent or with the addition of polarity increasing Solvents (phenol component) or aromatic solvents (Isocyanate component) used. The with these binder systems made cores can be particularly easily from the molds remove.

In practice, those formulated according to EP-A-0 771 599 Binder systems, however, have a serious disadvantage: during casting They develop more smoke and smoke, so they found in many foundries were not used beyond the experimental stage.

To meet the ever higher environmental standards and health and safety requirements meet, there has been a growing interest for some years Binder systems that have little or no aromatic Contain hydrocarbons.

It was therefore the object of the present invention, a low-aromatics or develop a free binder system. It is still a task of the invention to provide a binder system, which in the Casting has a low smoke formation. The with the help of this Binder system produced moldings should also have a good Bending strength, especially instant resistance, have.

This object has been achieved by a binder system comprising a Phenolic resin component and a polyisocyanate component in that the phenolic resin component and / or the polyisocyanate component comprises a fatty acid ester and the phenolic resin component comprises an alkoxy-modified phenolic resin wherein less than 25 mol% of the hydroxymethyl groups in the phenolic resin a primary or secondary aliphatic alcohol of 1 to 10 Are etherified carbon atoms and wherein the solvent content of the Phenolic resin component is at most 40 wt .-%.

Furthermore, the invention relates to molding compositions, the aggregates and up to 15 Wt .-% based on the weight of the aggregates of an inventive Binder system include.

a. Vermischen von Aggregaten mit dem erfindungsgemäßen Bindemittelsystem in einer bindenden Menge von bis zu 15 Gew.-%, bezogen auf die Menge der Aggregate;

b. Einbringen des in Schritt (a) erhaltenen Gießgemischs in eine Form;

c. Härten des Gießgemischs in der Form, um eine selbsttragende Form zu erhalten; und

d. anschließendes Entfernen des geformten Gießgemischs von Schritt (c) aus der Form und weiteres Härten, wodurch man ein hartes, festes, ausgehärtetes Gießformteil erhält.

The invention also relates to methods for producing a mold part comprising

a. Mixing aggregates with the binder system according to the invention in a binding amount of up to 15% by weight, based on the amount of the aggregates;

b. Introducing the casting mixture obtained in step (a) into a mold;

c. Curing the foundry mixture in the mold to obtain a self-supporting form; and

d. then removing the molded casting mix from step (c) from the mold and further curing, thereby obtaining a hard, solid, cured casting part.

The casting molding thus obtained can according to the invention for casting metal be used.

Essential to the invention is the choice of the alkoxy-modified phenolic resin, the has a low viscosity and favorable polarity. According to the invention allows the alkoxy-modified phenolic resin that needed Total solvent amount in both the phenolic resin component as also reduce in the isocyanate component. Furthermore, on the Use of aromatic hydrocarbons in one or both Binder components are dispensed with. By combining the alkoxy-modified phenolic resin with oxygen-rich, polar, organic Solvents are improved with reduced smoke formation Achieved instant strength. The addition of fatty acid ester has a positive effect the release effect and the moisture resistance.

Phenolic resins are made by condensation of phenols and aldehydes (Ullmann's Encyclopedia of Industrial Chemistry, Vol. A19, page 371 ff, 5th edition, VCH Verlag, Weinheim). In the context of this invention Besides phenol, substituted phenols and mixtures thereof may also be used be used. Suitable are all conventionally used substituted phenols. The phenolic compounds are either in both ortho positions or unsubstituted in an ortho and in the para position, to allow the polymerization. The remaining ring carbons may be substituted. The choice of the substituent is not particular if the substituent limited the polymerization of the phenol and the Aldehyds are not adversely affected. Examples of substituted phenols are alkyl-substituted phenols, aryl-substituted phenols, cycloalkyl-substituted Phenols, alkenyl-substituted phenols, alkoxy-substituted phenols, aryloxy-substituted Phenols and halogen-substituted phenols.

wobei A, B und C Wasserstoff, Alkylradikale, Alkoxyradikale oder Halogen sein können.The abovementioned substituents have 1 to 26, preferably 1 to 12, carbon atoms. Examples of suitable phenols besides the most preferred unsubstituted phenols are o-cresol, m-cresol, p-cresol, 3,5-xylene, 3,4-xylene, 3,4,5-trimethylphenol, 3-ethylphenol, 3,5 Diethylphenol, p-butylphenol, 3,5-dibutylphenol, p-amylphenol, cyclohexylphenol, p-octylphenol, 3,5-dicyclohexylphenol, p-crotylphenol, p-phenylphenol, 3,5-dimethoxyphenol, 3,4,5-trimethoxyphenol , p-ethoxyphenol, p-butoxyphenol, 3-methyl-4-methoxyphenol and p-phenoxyphenol. Particularly preferred is phenol itself. The phenols can also be described by the general formula:

where A, B and C may be hydrogen, alkyl radicals, alkoxy radicals or halogen.

As aldehyde according to the invention Formaldehyde used.

Particularly preferred is formaldehyde either in its aqueous form or as paraformaldehyde.

In order to obtain the phenolic resins according to the invention, an at least equivalent number of moles of formaldehyde, based on the number of moles of Phenol component, can be used. The molar ratio is preferably Formaldehyde: Phenol, therefore, at least 1: 1.0, more preferably at least 1: 0.58.

To obtain alkoxy-modified phenolic resins, primary and secondary aliphatic alcohols having one OH group and from 1 to 10 Carbon atoms used. Suitable primary or secondary alcohols include e.g. Methanol, ethanol, n-propanol, iso-propanol, n-butanol and Hexanol. Preference is given to alcohols having 1 to 8 carbon atoms, especially methanol and butanol.

The preparation of alkoxy-modified phenolic resins is described in EP-B-0 177 871 described. You can either use the one-step or two-step process getting produced.

In the one-step process, the phenol component, the formaldehyde and the alcohol in the presence of a suitable catalyst for the reaction brought. In the two-step process, first, a non-modified Resin prepared, which is then treated with alcohol.

Suitable catalysts are salts of divalent ions of Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca and Ba. Preferably, zinc acetate is used.

The alkoxylation leads to resins with a low viscosity. The resins have mainly ortho-ortho Benzyletherbrücken and also have ortho and para to the phenolic OH group alkoxymethylene groups of the general formula - (CH ₂ O) _n R on. Here, R is the alkyl group of the alcohol and n is a small integer in the range of 1 to 5.

All solvents which are conventionally used in binder systems for foundry technology can be used in the systems according to the invention. It is even possible to use aromatic hydrocarbons as a solvent component in larger proportions, but this does not avoid the above-mentioned, potentially environmentally and health-endangering solvents. As solvents for the phenolic resin component therefore oxygen-rich, polar, organic solvents are preferably used. Particularly suitable are dicarboxylic acid esters, glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters (lactones) or cyclic carbonates. Dicarboxylic acid esters, cyclic ketones and cyclic carbonates are preferably used. Dicarboxylic acid esters have the formula R ₁ OOC-R ₂ -COOR ₁ , wherein each R ₁ independently represents an alkyl group having 1-12 (preferably 1-6) carbon atoms and R _{2 is} an alkylene group having 1-4 carbon atoms. Examples are dimethyl esters of carboxylic acids having 4 to 6 carbon atoms which are obtainable, for example, under the name Dibasic Ester from DuPont. Glycol ether esters are compounds of the formula R ₃ -OR ₄ -OOCR ₅ where R _{3 is} an alkyl group of 1-4 carbon atoms, R _{4 is} an alkylene group of 2-4 carbon atoms and R _{5 is} an alkyl group of 1-3 carbon atoms (eg butyl glycol acetate ), preferred are glycol ether acetates. Glycol diesters correspondingly have the general formula R ₅ COO-R ₄ -OOCR ₅ , wherein R ₄ and R _{5 are} as defined above and the radicals R _{5 are} each independently selected (eg propylene glycol diacetate), glycol diacetates are preferred. Glycol diethers can be characterized by the formula R ₃ -OR ₄ -OR ₃ in which R ₃ and R _{4 are} as defined above and the radicals R _{3 are} each independently selected (eg dipropylene glycol dimethyl ether). Cyclic ketones, cyclic esters and cyclic carbonates of 4-5 carbon atoms are also suitable (eg, propylene carbonate). The alkyl and alkylene groups may each be branched or unbranched. These organic polar solvents are preferably used either as a sole solvent for the phenolic resin or in combination with fatty acid esters, wherein the content of the oxygen-rich solvents in the solvent mixture should predominate. The content of oxygen-rich solvents should thus be more than 50% by weight, preferably more than 55% by weight.

The measure had a positive effect on the development of quality, the To reduce the total content of solvents in the binder system. While conventional phenolic resins predominantly about 45 wt .-% and partially up to 55 wt .-% solvent to a Processing-compatible viscosity (up to about 400 mPa · s) can be achieved by Use of a low-viscosity phenolic resin of the invention Solvent content in the phenol component to at most 40 wt .-%, preferably even limited to at most 35 wt .-%. The dynamic Viscosity is e.g. determined by the Brookfield rotary spindle method.

If conventional non-alkoxy-modified phenolic resins are used, the viscosity at a reduced solvent content is far outside the range of application-favorable ranges of up to about 400 mPa · s. Partly, the solubility is so poor that phase separation is observed at room temperature. At the same time, the instant strengths of the cores made with these binder systems are reduced to a very low level. Suitable binder systems have an instantaneous strength of at least 150 N / cm ² at a used amount of each 0.8 parts by weight of phenolic resin component and isocyanate component, based on 100 parts by weight of aggregate, such as quartz sand H 32 (see EP-A-0 771 599 or DE -A-4 327 292).

The addition of fatty acid ester to the solvent of the phenolic component leads to particularly good release properties. Suitable fatty acids are e.g. with 8 to 22 carbons esterified with an aliphatic alcohol. Usually fatty acids of natural origin, e.g. from tall oil, Rapeseed oil, sunflower oil, germ oil and coconut oil. Instead of the natural oils, which are mostly mixtures of different fatty acids, Of course, single fatty acids, e.g. palmitic or myristic fatty acid.

Aliphatic monoalcohols with 1 to 12 carbons are suitable for Esterification of fatty acids. Preference is given to alcohols having 1 to 10 Carbon atoms, particularly preferred are alcohols having 4 to 10 Carbon atoms. Due to the lower polarity of the fatty acid esters, whose alcohol component has 4 to 10 carbon atoms, it is possible to reduce the fatty acid ester content and reduce the formation of smoke. A number of fatty acid esters are commercially available.

Surprisingly, it was found that fatty acid esters whose Alcohol component contains 4 to 10 carbon atoms, particularly advantageous because they are excellent for the binder system Impart release properties when their content in the solvent of the Phenol component is less than 50 wt .-% is. As examples of Fatty acid esters with longer alcohol components are the butyl esters of Oleic acid and tall oil fatty acid and the mixed octyl / decyl ester of Called tall oil fatty acid.

By the use of the alkoxy-modified Phenolic resins can be aromatic hydrocarbons as a solvent avoid the phenol component. This is due to the balanced polarity of the Due to the use of oxygenated, organic, polar solvents e.g. as a sole solvent. By the use of the alkoxy-modified Phenolic resins can reduce the amount of solvent needed to less than 35 wt .-% of phenol component are limited. This is done by the low viscosity of the resin allows. The use of aromatic Hydrocarbons can also be avoided. The use of the binder system according to the invention with at least 50 wt .-% of above-mentioned oxygen-rich, polar, organic solvent as Part of the solvent of the phenol component also leads to a significantly reduced smoke development compared to conventional Systems with a high proportion of fatty acid esters in the solvent.

The second component of the binder system comprises an aliphatic, cycloaliphatic or aromatic polyisocyanate, preferably with 2 to 5 Isocyanate groups. Depending on the desired properties can also Mixtures of organic isocyanates are used. suitable Polyisocyanates include aliphatic polyisocyanates, e.g. Hexamethylene diisocyanate, alicyclic polyisocyanates such as e.g. 4,4'-dicyclohexylmethane and dimethyl derivatives thereof. Examples suitable aromatic polyisocyanates are toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, Xylylene diisocyanate and methyl derivatives thereof, Polymethylene polyphenylisocyanate and chlorophenylene-2,4-diisocyanate. Preferred polyisocyanates are aromatic polyisocyanates, especially preferred are polymethylene polyphenyl polyisocyanates, e.g. Diisocyanate.

In general, 10-500% by weight of polyisocyanate is by weight used the phenolic resin. Preferably, 20-300% by weight Polyisocyanate used. Liquid polyisocyanates can be undiluted Form while solid or viscous polyisocyanates in be dissolved organic solvents. Up to 80% by weight of the isocyanate component may consist of solvents. As a solvent for the Polyisocyanate will be either the above-mentioned fatty acid esters or a Mixture of fatty acid esters and up to 50% by weight of aromatic solvents used. Suitable aromatic solvents are naphthalene, alkyl-substituted Naphthalenes, alkyl-substituted benzenes and mixtures thereof. Particularly preferred are aromatic solvents consisting of mixtures of consist of above-mentioned aromatic solvents and a Boiling point range between 140 ° C and 230 ° C have. Preferably no aromatic solvent used. This is preferred Polyisocyanate used in an amount such that the number of Isocyanate groups from 80 to 120%, based on the number of free Hydroxyl groups of the resin.

In addition to the components already mentioned, the binder systems conventional additives, such. B. silanes (US 4,540,724), drying oils (US 4,268,425) or complexing agents (WO 95/03903). The Binder systems are preferred as two-component systems offered, wherein the solution of the phenolic resin is a component and the polyisocyanate, optionally in solution, is the other component. The two components are combined and then sand or a similar aggregate mixed to produce a molding material. The Molding composition contains an effective binding amount of up to 15 wt .-% of binder system according to the invention, based on the weight of Aggregates. It is also possible to use the components first with each Mixing of the sand or aggregate and then this to unite both mixtures. Method to a uniform mixture to achieve the components and the aggregate are those skilled in the art known. In addition, the mixture may optionally contain other conventional Ingredients, such as iron oxide, ground flax fibers, wood pieces, and pitch refractory flours, included.

To make moldings from sand, the aggregate should have enough have large particle size. As a result, the mold part has a Sufficient porosity and volatile compounds may occur during the Casting escape. Generally, at least 80% by weight and preferably 90% by weight of the aggregate an average Particle size ≤ 290 microns on. The average particle size of the Aggregates should be between 100 and 300 μm.

For standard molded parts sand is preferred as aggregate material used, wherein at least 70 wt .-% and preferably more than 80 wt .-% of the sand are silica. Zircon, olefin, aluminosilicate sand and Chromite sand are also suitable as aggregate materials.

The aggregate material is the main ingredient in molded parts. In Molded sand moldings for standard applications account for the share of Binder generally up to 10 wt .-%, often between 0.5 and 7 Wt .-%, based on the weight of the aggregate. Especially preferred are 0.6 to 5 wt .-% of binder, based on the weight of Aggregates, used.

Although the aggregate is preferably dried, up to 0.1 wt .-%, based on the weight of the aggregate, tolerated by moisture become. The mold part is hardened so that it conforms to its external shape the removal of the mold retains. Conventional liquid or gaseous Hardening systems can be used to cure the invention Binder system can be used. Thus, e.g. a volatile one tertiary amine, e.g. Triethylamine or dimethylethylamine as described in US-A-3,409,579 described, are passed through the mold part. It is furthermore possible to add a liquid amine to the molding compound for curing. After removal from the mold is in a conventional manner the Molded part converted by further hardening in the final state.

In a preferred embodiment, silanes of the general formula (R'O) ₃ Si are added to the molding compound before curing. Here, R 'is a hydrocarbon radical, preferably an alkyl radical of 1-6 carbon atoms, and R is an alkyl radical, an alkoxy-substituted alkyl radical or an alkylamine-substituted amine radical having alkyl groups having 1-6 carbon atoms. The addition of 0.1 to 2% by weight, based on the weight of the binder system and the hardener, reduces the moisture sensitivity of the systems. Examples of commercially available silanes are Dow Corning Z6040 and Union Carbide A-187 (γ-glycidoxypropyltrimethoxysilane), Union Carbide A-1100 (γ-aminopropyltriethoxysilane), Union Carbide A-1120 (N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane) and Union Carbide A-1160 (ureidosilane).

Optionally, other additives including wetting agents and the use of the sand mixture extending additives (engl. Benchlife additives), as described in US 4,683,252 or US 4,540,724, be used. Additional mold release agents such as e.g. fatty acids, Fatty alcohols and their derivatives can be used, but are used in usually not needed.

The invention is further illustrated by the following examples.

Examples

Unless otherwise stated, all percentages are understood as Wt .-%.

1. Preparation of phenolic resins

In a reactor equipped with reflux condenser, thermometer and stirrer, the raw materials listed in Table I are presented. With stirring, the temperature is raised evenly to 105-115 ° C and held until a refractive index of 1.5590 is reached. Thereafter, the condenser is switched to distillation and the temperature within one hour at 124 - 126 ° C brought. At this temperature is further distilled until reaching a refractive index of 1.5940. Thereafter, vacuum is applied and distilled under reduced pressure to a refractive index of 1.600. The yield is about 83% in example 1 and about 78% in example 2. example 1 2 not according to the invention inventively phenol 2130.7 g 1770.6 g Paraformaldehyde 91% 865.3 g 984.3 g n-butanol - 279.6 g Zinc acetate dihydrate 1.0 g 1.5 g

2. Preparation of phenolic resin solutions

The phenolic resins prepared according to the above specification are used to prepare the solutions listed in Table II. Trade names are indicated by (H).

The phenol resin solution 1A separates after cooling to room temperature in two phases and is therefore not used for further tests. The viscosity of the phenol resin solutions 1B-1D is far outside the application-favorable range (up to approx. 400 mPa · s)

3. Preparation of the polyisocyanate solutions

As component II of the polyurethane binder systems, the solutions listed in Table III are prepared. example 3A 3B 3C inventively diisocyanate
(technical MDI) 80% 80% 80% Forbiol 102 (H) 19.8% 10% Forbiol 152 (H) 19.8% Solvesso 100 (H) 9.8% acid chloride 0.2% 0.2% 0.2%

4.) Preparation and testing of the molding material / binder system mixtures

In the preparation of the molding material / binder system mixtures, the following is done The procedure:

To 100 parts by weight of quartz sand H 32 (Quarzwerke GmbH, Frechen) in each case 0.5 parts by weight of one of those listed in Table II Phenolic resin solutions and 0.8 parts by weight of one of those listed in Table III Polyisocyanate added and intensively in a laboratory mixer mixed. With these mixtures are test specimens according to DIN 52401 prepared by gassing with triethylamine (10 s at 4 bar pressure, then 10 s rinsing with air) are cured.

The flexural strengths of the specimens are determined by the GF method. The bending strength of the specimens immediately after their Production (immediate strength) as well as tested after 1, 2 and 24 hours.

The results are listed in Table IV. attempt 1 2 3 4 5 6 7 8th 9 10 11 12 13 Component 1 1B 1 C 1D 2A 2 B 2C 2D 2E 2F 2G 2H 2D 2D Component 2 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3A 3B 3C not according to the invention inventively Strengths (N / cm ² ) immediately 105 120 140 205 235 225 205 225 200 230 180 190 210 1 h 380 355 390 555 575 565 580 560 555 530 430 580 500 2 h 400 405 400 555 575 565 580 560 570 590 440 585 530 24 hours 555 540 530 590 630 610 590 570 570 600 550 590 570

• die mit dem herkömmlichen Phenolharz formulierten Bindemittelsysteme (Versuch 1-3) besitzen wesentlich geringere Anfangsfestigkeiten als die erfindungsgemäßen Bindemittelsysteme (Versuche 4-13). Auch der Festigkeitsanstieg ist deutlich langsamer.
• die Festigkeiten, vor allem die Sofortfestigkeiten, aller erfindungsgemäß formulierten Bindemittelsysteme (Versuche 4-13) sind innerhalb der Genauigkeit der Prüfmethode gleich. Eine Abhängigkeit vom Verhältnis - Fettsäureester/polares Lösungsmittel ist nicht erkennbar.
• sowohl der Fettsäurebutylester als auch der Fettsäureoctyl-/decylester sind für die Formulierung der erfindungsgemäßen Bindemittelsysteme gleichermaßen geeignet (Versuche 7 und 12)
• die Kombination mit aromatischen Lösungsmitteln ist ebenso möglich (Versuche 7 und 13)

From Table III it can be seen:

• the binder systems formulated with the conventional phenolic resin (Tests 1-3) have significantly lower initial strengths than the binder systems according to the invention (Experiments 4-13). The strength increase is also much slower.
• the strengths, especially the immediate strengths, of all binder systems formulated according to the invention (Tests 4-13) are the same within the accuracy of the test method. A dependence on the ratio - fatty acid ester / polar solvent is not recognizable.
• Both the fatty acid butyl ester and the fatty acid octyl / decyl ester are equally suitable for the formulation of the binder systems according to the invention (experiments 7 and 12).
• the combination with aromatic solvents is also possible (experiments 7 and 13)

5. Observation of the development of quality

GF test bars are stored in the oven for 1 minute at 650 ° C. After Withdrawal becomes the smoke development against a dark background observed and with the grades 10 (very strong) - 1 (barely perceptible) rated.

The result is listed in Table V. Cores from experiment (Tab. IV) 4 5 6 7 8th 9 10 11 12 Component 1 2A 2 B 2C 2D 2E 2F 2G 2H 2D Component 2 3A 3A 3A 3A 3A 3A 3A 3A 3B rating 10 8th 8th 5 5 5 5 5 5

From Table V shows that the development of smoke subsides, if the Fatty acid ester reduced in favor of oxygen-rich solvent.

Casting experiments with cores containing the composition of experiments 4 and 7, confirmed the above result.

Claims (8)

1. Binder system comprising one phenol resin component and one polyisocyanate component, characterised in that the phenol resin component and/ or the polyisocyanate component comprises a fatty acid ester and the phenol resin component comprises an alkoxy-modified phenol resin, less than 25% by mol of the hydroxymethyl groups in the phenol resin being etherified by means of a primary or secondary aliphatic monoalcohol with 1 to 10 carbon atoms, and the solvent component of the phenol resin component being at most 40% by weight.
2. Binder system according to claim 1, the phenol resin component comprising a polar, organic solvent, the polar organic solvent being selected from dicarbonic acid ester, glycol ether ester, glycol diester, glycol diether, cyclic ketones, cyclic esters and cyclic carbonates.
3. Binder system according to claim 2, the phenol resin component comprising a fatty acid ester.
4. Binder system according to claim 3, the radical of the fatty acid ester, which is derived from the alcohol, containing 1 to 12 carbon atoms.
5. Moulding compound comprising aggregates and an effective binding quantity of up to 15% by weight relative to the weight of the aggregates of a binder system according to one of the claims 1 to 4.
6. Method for producing a casting mould part comprising

   a. mixing of aggregates with the binder system according to one of the claims 1 to 4 in a binding quantity of up to 15% by weight relative to the quantity of aggregates;

   b. introduction of the casting mixture obtained in step (a) into a mould;

   c. hardening of the casting mixture in the mould in order to obtain a self-supporting mould; and

   d. subsequent removal of the moulded casting mixture of step (c) from the mould and further hardening, as a result of which a hard, solid, cured casting mould part is obtained.
7. Method according to claim 6, in which the casting mixture is hardened by means of treatment of the casting mixture with an amine.
8. Method for casting a metal, comprising:

   a. production of a casting mould part according to one of the claims 6 or 7;

   b. casting of metal in the fluid state in or around this mould;

   c. cooling and setting of the metal; and

   d. subsequent separation of the cast object.