Foundry binder system

Abstract

The present invention relates to a binder system comprising a polyol and an isocyanate polymer with a free monomer content of less than 0.1% for the foundry industry, particularly for producing foundry moulds, such as cores and / or moulds, for both ferrous and non-ferrous alloys. The invention also relates to cores and / or moulds comprising said binder system and a process for producing said cores and / or moulds. The foundry cores and / or moulds of the present invention are formed by industrially known processes using liquid amines ("no-bake" process) or vapor-phase amines ("cold box" process).

Description

[0001] Title

[0002] Foundry binder system

[0003] Description

[0004] The present invention relates to a binder system comprising a polyol and an isocyanate polymer with a free monomer content of less than 0.1 % for the foundry industry, particularly for producing foundry moulds, such as cores and / or moulds, for both ferrous and non-ferrous alloys.

[0005] The invention also relates to cores and / or moulds comprising said binder system and a process for producing said cores and / or moulds.

[0006] The foundry cores and / or moulds of the present invention are formed by industrially known processes using liquid amines (“no-bake” process) or vapor-phase amines (“cold box” process).

[0007] STAT OF THE ART

[0008] The REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) Restriction No. 74 on diisocyanates was adopted by the REACH Committee on February 4, 2020, and it was published in the Official Journal on August 3, 2020. According to the Agency’s decision, after August 24, 2023, diisocyanates are not to be used, either as a pure substance or in mixtures, unless industrial workers or professionals have completed specific training and have adopted adequate handling and protection systems. This restriction does not apply to products containing diisocyanates at a concentration of less than 0.1 % by weight.

[0009] Products containing high levels of monomer, and in any case above 0.1 %, are potentially carcinogenic, highly toxic, and may cause allergy or asthma symptoms, or even serious breathing difficulties. Toxicity typically varies with molecular weight due to both vapor pressure and volatility. For example, both toluene diisocyanate (TDI, molecular weight 174.2 g / mol) and hexamethylene diisocyanate (HDI, molecular weight 168.2 g / mol) are volatile at room temperature, while diphenylmethane diisocyanate (MDI, molecular weight 250.3 g / mol) must be heated before significant amounts evaporate. Furthermore, the hazards of TDI and MDI are not limited to the pure substances, but also to the hot decomposition products of both the isocyanates themselves and derivative molecules thereof, which are typically highly toxic and carcinogenic aromatic monomers and amines. Reducing the overall amount of monomers, but more generally of isocyanates, has therefore a considerable impact on the quality of emissions into the workplace and the atmosphere.

[0010] Since volatile monomers pose serious industrial hygiene problems, isocyanates are often supplied in modified forms; for example, in the form of oligomers, polymers, but also prepolymers, or polymer adducts, obtained by reacting isocyanate with polyols. This expedient effectively results in an increase in molecular weight and a corresponding reduction in volatility. This explains the almost exclusive use of polymeric MDI (CAS# 9016-87-9), indicated by the acronym PMDI, in the foundry sector, as described for example in EP1057554B1 .

[0011] However, as described in EP0420026B1 , if special measures such as stripping or removal by reaction with chemical sequestrants are not taken, free monomers are still present in the PMDI product. The PMDI polymer is, in fact, very approximately made of 50% monomeric MDI, 30% triisocyanate, 10% tertiary isocyanate, 5% pentaisocyanate, and 5% higher homologues (homologues, in this case, are intended to be molecules with a weight greater than that of pentaisocyanate) and with a typical average functionality of 2.7. On the other hand, the removal of monomers from polymeric isocyanates, particularly from PMDI (CAS 9016-87-9), generates extremely viscous products that are unusable in foundries. Fractions with a weight greater than the monomer are in fact very viscous or solid. High viscosity results in poor foundry products because the sand and the urethane binder mixtures have poor flowability, the binder is not distributed homogeneously, the developed mechanical strengths are very low, and the cross-linking processes are very slow due to the low mobility of the heavy molecules and their functional groups.

[0012] CA1160796 describes resin binder compositions that are blends of polyols and isocyanate-urethane polymers with unspecified monomer levels.

[0013] There is therefore a clear need to provide new foundry binder systems with reduced monomer and isocyanate content.

[0014] SUMMARY OF THE INVENTION

[0015] The aim of this invention is to provide new foundry binder systems comprising a polyol component (Part A) and an isocyanate component (Part B), wherein the isocyanate component has a monomeric isocyanate content of less than 0.1 %.

[0016] Unlike traditional systems, the isocyanate component with a free monomer content of less than 0.1 % is not classified as carcinogenic and is significantly less hazardous, not causing serious allergy or asthma symptoms or serious breathing difficulties.

[0017] In fact, the only risk phrases applicable to the product under consideration are H317 (May cause an allergic skin reaction) and H319 (Causes serious eye irritation). The traditional system, however, is potentially carcinogenic (H351 ); may cause allergy or asthma symptoms or even serious breathing difficulties (H334); harmful if inhaled (H332), may cause respiratory irritation (H335); may cause damage to the respiratory tract through prolonged or repeated exposure (H373); may cause an allergic skin reaction (H317); causes serious eye irritation (H319); and causes skin irritation (H315). Advantageously, despite the removal of the monomer, the system guarantees good mechanical resistance and significantly reduces both odours and emissions of aromatic amines during the forming phase.

[0018] The above-described purpose is achieved with a foundry binder system according to claim 1 , with the use of said binder system for producing foundry cores and / or moulds according to claim 9, with foundry cores and / or moulds comprising said binder system according to claim 10, with a process for the production of foundry cores and / or moulds according to claims 11 and 12.

[0019] DEFINITIONS

[0020] Unless otherwise defined, all terms of the art, notations and other scientific terminology used herein are intended to have the meanings commonly understood by those skilled in the art to which this disclosure pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or for ready reference; thus, the inclusion of such definitions in the present disclosure should not be construed to represent a substantial difference over what is generally understood in the art.

[0021] The terms “approximately” and “about” used in the text refer to the range of the experimental error that is inherent in the execution of an experimental measurement.

[0022] The terms “comprising”, “having”, “including” and “containing” are to be intended as open-ended terms ( / .e., meaning “comprising, but not limited to”), and are to be considered as a support also for terms such as “consist essentially of”, “consisting essentially of”, “consist of”, or “consisting of”.

[0023] The terms “consist essentially of”, “consisting essentially of” are to be intended as semi-closed terms, meaning that no other ingredients affecting the novel features of the invention are included (optional excipients may therefore be included). The terms “consists of”, “consisting of’ are to be intended as closed terms.

[0024] The term “free monomer” refers to the amount of monomeric isocyanate remaining after a chemical polymerization, addition, or physical separation process, such as distillation, involving the same isocyanate.

[0025] The term "active content" refers to the amount of monomeric, oligomeric, polymeric, prepolymer, or polymeric adduct isocyanate or other reactive form present in a formulation. It is generally expressed as a percentage. The remaining fraction is typically made up of solvents and additives such as adhesion promoters, wetting agents, release agents, catalysts, or reaction inhibitors.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] An object of the present invention is represented by the foundry binder systems as defined below.

[0028] The foundry binder system according to the invention comprises a polyol component (Part A) and an isocyanate component (Part B), wherein the isocyanate component has a monomeric isocyanate content of less than 0.1 %.

[0029] In a preferred embodiment, the isocyanate component has an isocyanate-urethane active content of less than 80%, preferably between 60% and 24%, more preferably between 48% and 24%, and even more preferably between 48% and 39%.

[0030] The base of the isocyanate component is obtained industrially by reacting one or more isocyanates with one or more polyols to form a urethane compound, oligomer, or prepolymer (or polymer adduct) that still contains reactive free isocyanates (as described, for example, in EP0420026B1 and W02021 / 051039). The free isocyanates are available for reaction with the polyol component, Part A.

[0031] Examples of base compounds that may be used in the present invention are the oligomer obtained by the reaction of toluene diisocyanate with 2,2’-oxydiethanol and trimethylolpropane (CAS 53317-61-6); poly(hexamethylene diisocyanate) (CAS 28182-81-2); and polypropylene glycol)tolylene 2, 4-di isocyanate terminated (CAS 9057-91-4).

[0032] A monomer content below 0.1 % can be achieved by adding sequestering reagents and / or subjecting the product to extraction or distillation under very high vacuum, typically by thin-film evaporation.

[0033] A method that can be used to determine the free monomer content is according to ISO 10283: Binders for paints and varnishes — Determination of monomeric diisocyanates in isocyanate resins.

[0034] Polyols useful for preparing the isocyanate Part B include, for example, glycols, glycerol, polyglycols, carbohydrates, polyester polyols, polyether polyols, polycaprolactone, aminopolyols, polyamines, oligomers, and polymers of various nature with hydroxyl groups, as well as their corresponding thiol compounds. Glycols, glycerin, and trimethylolpropane are generally preferred.

[0035] Organic diisocyanates suitable for the purposes of the present invention include, for example, toluene diisocyanate (TDI), such as 80:20 and 65:35 mixtures of the 2,4- and 2,6-isomers, ethylene diisocyanate, propylene diisocyanate, diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate (pPDI), methylene bis(4- cyclohexyl)isocyanate (CHDI), xylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate, and mixtures thereof.

[0036] TDI is the preferred diisocyanate.

[0037] To prepare typical polyurethane prepolymers, it is preferred to use an isomeric mixture of 2,4- and 2,6-TDI in which the weight ratio of the 2,4-isomer to the 2,6- isomer ranges from about 45:55 to about 90:10, and more preferably from about 65:35 to about 80:20. In a preferred embodiment, the concentration of the isocyanate adduct, or prepolymer, in the solution ranges from 24 to 60%, preferably from 24 to 48%, more preferably from 39 to 48%.

[0038] In a preferred embodiment, the isocyanate component is obtained by dilution from a prepolymer, or polymer adduct, using at least one solvent with a prepolymer / adduct:solvent weight ratio in the range of 1 :4.4 to 1 :1.8, preferably in the range of 1 :2.6 to 1 :2.1.

[0039] In a preferred embodiment, after appropriate formulation, the isocyanate component of the system has a viscosity between 10 and 1200 mPa s at 23°C, preferably between 50 and 600 mPa s at 23°C.

[0040] Preferably, the TDI prepolymer or polymer adduct has an initial isocyanate (NCO) group content of 10.0-10.8%, which ranges from 9.5-10.3% up to a limit of 4.0-4.3% after dilution with the solvent.

[0041] TDI is marketed as a mixture of two isomers: 2,4-toluene diisocyanate (CAS# 584- 84-9) and 2,6-toluene diisocyanate (CAS# 91 -08-7). Typically, they are in a ratio of 80 / 20, but it can be also 65 / 35. The 2,4-TDI isomer is more reactive than 2,6-TDI. Furthermore, unlike the MDI molecule, which has equivalent isocyanates, the two isocyanates present on the TDI molecule have different reactivities. For example, the 4-position can be up to four times more reactive than the 2-position. Once the first isocyanate has reacted, the second is even less reactive (it is estimated to be about eight times less reactive). The reactivity of isocyanates is, in fact, favoured by electron-withdrawing groups. The reaction of the first isocyanate with a polyol results in the formation of a urethane, which is a weaker electron withdrawer than the isocyanate itself. In the light of the above, reactions leading to the formation of TDI oligomers, polymers, and prepolymers favour the reactions of the most reactive sites of 2,4- toluene diisocyanate, which is also the most abundant product in the reaction mixture (80 / 20 or 65 / 35). Free, poorly reactive isocyanates will remain in the finished product. A major obstacle to the use of TDI polymers and oligomers with a free monomer content of less than 0.1 % is identified by the dual function that TDI monomers play in the reaction mixture.

[0042] Monomers, in fact, reduce the viscosity of the mixture by increasing the mobility of the molecules present and increasing the reaction rate of the system.

[0043] Foundry formulations obtained from the traditional PMDI system (CAS# 9016-87-9) typically have a reactive isocyanate component content, i.e. the active content, of between 60 and 100% by weight, and an isocyanate group (NCO) content of between 17 and 33% by weight.

[0044] Table A - Typical properties of the traditional PMDI isocyanate, CAS# 9016-87-9, and the TDI adduct with CAS# 53317-61-6 in solution, according to the subject matter of the present invention

[0045] The present inventors have surprisingly found that by operating with dilutions that bring the active content to between 24 and 57%, and consequently have a reactive isocyanate content of between 10.3% and 4.0%, formulations suitable for foundry use are obtained. The isocyanate component B is formulated by dilution with a suitable solvent to obtain a viscosity suitable for use (typically less than 500 mPa s at 23°C). The preferred solvents are esters of both vegetable and animal, saturated or unsaturated fatty acids, (for example, soybean oil methyl ester, rapeseed oil methyl ester, sunflower oil methyl ester, oleic acid methyl ester, myristic acid isopropyl ester, lauric acid isopropyl ester, etc.), vegetable oils (linseed oil, soybean oil, etc.), aliphatic esters (esters of C3-C6 dicarboxylic acids, dioctyl adipate, acetates, glycerol triacetate, glycol esters, esters of glycol ethers, acrylic esters, etc.), aromatic esters (diethyl phthalate, ethylhexyl trimellitate, etc.), cyclic ketones, isophorone, lactones, cyclic carbonates, silicic acid esters, and oligomeric products thereof, and mixtures thereof, alkanes and cycloalkanes, aromatic solvents (typically alkyl benzenes, light naphtha solvent, heavy naphtha solvent), and mixtures thereof. Dicarboxylic acid esters and rapeseed oil methyl esters are the preferred solvents.

[0046] Advantageously, Part B of the system is non-carcinogenic and, being an extended and low-volatile polymer, it significantly reduces the risk of causing allergy or asthma symptoms or breathing difficulties.

[0047] It is not subject to restriction No. 74; therefore, no user training is required.

[0048] The polyol component A is selected from the group comprising glycols, polyglycols, polyols, saccharide polyols, polyether polyols, polyester polyols, polyols from PET, polyols from cashew oil or cardanol, biopolyols, aminopolyols, phenolic polymers and oligomers of a benzyl ether nature, alkoxylated novolacs, resol resins, hydroxylated epoxy resins, phenoxy resins, alkyd resins and mixtures thereof, as well as their corresponding thiol compounds.

[0049] For light metals (aluminium and alloys) casting, traditional sucrose polyols and / or aminopolyols may be used. For high-melting metals (cast iron, steel) casting, benzyl ether phenolic resins (described, for example, in patent EP1057554B1 ), epoxy resins, phenoxy resins, or combinations thereof can, for example, be successfully used.

[0050] The present inventors have surprisingly identified an isocyanate with a low free monomer content that, due to its structure, when appropriately combined with suitable polyols and a suitable catalyst, can be formulated to ensure adequate strength comparable to that of traditional systems, while maintaining good sand flowability and adequate cross-linking times.

[0051] The present inventors have surprisingly found that removal of monomers from polymeric isocyanates generates extremely viscous and unusable products. High viscosity produces poor-quality products because the mixtures with sand have a poor flowability, the binder is distributed unevenly, the mechanical strengths developed are very low, and the cross-linking processes are very slow due to the low mobility of the heavy polymer molecules and related functional groups. Viscosity can be reduced by dilution with solvents. However, achieving viscosities suitable for foundry use (typically <500 cPs at 23°C) requires dilutions that significantly reduce both the active material content and the availability of reactive sites.

[0052] According to a preferred aspect, the binder system of the invention may also include additives.

[0053] According to a preferred aspect of the present invention, additives are intended to be substances and / or compounds useful for improving the performance of the binder system.

[0054] Examples of additives that can be used in the binder system of the invention are adhesion promoters, such as silanes, titanates, and zirconates; release agents; reaction inhibitors or accelerators / catalysts; and wetting agents. A further object of the invention is the use of the binder systems as defined above for producing foundry cores and / or moulds; in particular, for both ferrous and non-ferrous alloys A.

[0055] Further object of the invention are foundry cores and / or moulds comprising the binding systems of the invention and sand, and / or other refractory material.

[0056] Foundry moulds, such as cores and / or moulds, into or around which the molten metal will be poured, are made of a granular refractory material, such as silica sand and / or other granular refractory material, mixed with the binding system.

[0057] Foundry moulds should meet several requirements. In particular, in addition to sufficient stability and thermal resistance to accommodate the liquid metal, they should also be stable to humidity present in the processing environment, so that they can be used even long after their production, and even after having undergone mechanical stress due to their transportation to locations other than their production site for use.

[0058] A further object of the invention is a “cold box” process for producing said foundry moulds, such as cores and / or moulds, comprising a production step for moulding material mixtures comprising the binding systems of the invention along with silica sand and / or other granular refractory material, and a cross-linking step for said moulding material mixtures obtained by suspending a tertiary amine in a flow of inert gas and passing the gas flow containing the tertiary amine through the mould under sufficient pressure to force it into the moulded form, until the mixture has polymerized.

[0059] Suitable catalysts are gaseous tertiary amines or amines that can be introduced in the vapour state. The preferred tertiary amines in the “cold box” process are N,N- dimethylisopropylamine (DMIPA, CAS# 996-35-0), N,N-dimethylethylamine (DMEA, CAS# 598-56-1 ), dimethylpropylamine (DMPA, CAS# 926-63-6), triethylamine (TEA, CAS# 121-44-8).

[0060] A further object of the invention is a “no-bake” process for producing said foundry moulds, such as cores and / or moulds, wherein the binder system, catalyst, and sand and / or other refractory material are mixed together at room temperature.

[0061] Liquid tertiary amines and imidazole derivatives are the preferred catalysts in the “nobake” process, sometimes in combination with tin, manganese, cobalt, bismuth, and iron organometallic compounds.

[0062] Imidazole derivatives that may preferably be used are 1 -methylimidazole (CAS# 616- 47-7), solutions of 1 ,2-dimethylimidazole (CAS# 1739-84-0), ethylimidazole (CAS# 1072-62-4).

[0063] More preferably, tertiary amines such as 1 ,4-Diazabicyclo[2.2.2]octane (CAS# 280- 57-9), 1 ,3-bis[3-(Dimethylamino)propyl]urea (CAS# 52338-87-1 ), 2-[2-

[0064] (Dimethylamino)ethoxy]ethanol (CAS# 216-940-1 ), 2-

[0065] (Dimethylamino)ethylmethylaminoethanol (CAS# 2212-32-0), N,N- diisopropanolamine (CAS# 63469-23-8).

[0066] The results of the technological laboratory tests reported below clearly illustrate the advantages offered by the invention. The following examples are merely illustrative and not limitative of the present invention.

[0067] EXAMPLES a) Liquid amine catalysis - “no-bake” process

[0068] The components of the binder system, Part A, Part B, and Part C, are mixed with AFA55-type French sand in a laboratory paddle mixer. After a defined mixing time (2 minutes), the sand is transferred to a mould for the preparation of specimens. After cold curing, the specimens are subjected to mechanical testing to measure their breaking strength.

[0069] Table 1 - Tests carried out on AFA55-type French sand maintained at 20°C and 50% relative humidity according to the method VDG P72, October 1999, with amounts and times indicated.

[0070] Samples:

[0071] Rapidur P12 / A Commercial product, benzyl ether phenol formaldehyde polymer diluted in aliphatic and aromatic solvents (dibasic ester and

[0072] Solvesso 150).

[0073] Rapidur P / B Commercial product consisting of 70% MDI polymer with CAS

[0074] 9016-87-9 in aromatic solvents (Solvesso 150).

[0075] Rapidur SB2 / B Product of the invention obtained by mixing 75% of the base solution of the polymeric adduct of toluene diisocyanate with 2,2’-oxydiethanol and trimethylolpropane with CAS 53317-61-6 in dibasic ester and 25% rapeseed oil methyl ester. The product used as a base (developed for this purpose by Sapici SpA) has an active adduct content of 60%, an isocyanate content of 10.0-

[0076] 10.8%, a TDI monomer content of <0.08%, and a viscosity of

[0077] 1000-2000 mPa s at 23°C.

[0078] Rapidur I4N / C Catalyst based on 1 -methylimidazole (30% in dibasic ester solution) Rapidur I2N / C Catalyst based on 1 -methylimidazole (10% in dibasic ester solution)

[0079] Mechanical Testing for Breaking Strength

[0080] The test specimens are produced using the “no-bake” process and their bending strengths are determined at various times after forming. The production of the test specimens is performed in accordance with the technical standard VDG P72. For this purpose, the sand is loaded into a mixing vessel. The polyol component, the polyisocyanate component, and the tertiary amine used as a catalyst (Table 1 ) are weighed separately into the mixing vessel. Subsequently, the raw materials are mixed in a paddle mixer for 2 minutes to form the moulding mixture.

[0081] The specimens are produced by manually compacting the mixture into the mould made as described in the technical standard. The three-point bending strength is measured using a Benetlab Allinone instrument at specific times (1 hour, 2 hours, 24 hours, Table 1 ) after the end of forming. b) Amine vapor catalysis - “cold box” process

[0082] The components of the binder system, Part A and Part B, are mixed with AFA55-type French sand in a laboratory mixer. After a defined mixing time, the sand is transferred to a laboratory forming machine equipped with a mould for preparing specimens. After curing by passage of tertiary amine vapours, the specimens are subjected to mechanical testing to measure their breaking strength. Table 2 - Tests carried out on 100 g of AFA55-type French sand maintained at 20°C and 50% relative humidity according to the VDG P73 method, February 1996, with amounts and times indicated.

[0083] Samples:

[0084] Giocaset CB110A Commercial product, benzyl ether phenol formaldehyde polymer diluted in aliphatic solvents (dibasic ester, vegetable oil methyl ester)

[0085] Giocaset CB150 / B Commercial product consisting of 82% MDI polymer with CAS 9016-87-9 in aliphatic solvents (vegetable oil methyl ester)

[0086] Rapidur SB2 / B Product of the invention obtained by mixing 75% of the base solution of the polymer adduct of toluene diisocyanate with 2,2’- oxydiethanol and trimethylolpropane with CAS 53317-61-6 in dibasic ester and 25% rapeseed oil methyl ester. The product used as a base (developed specifically by Sapici SpA) has an active adduct content of 60%, an isocyanate content of 10.0- 10.8%, a TDI monomer content of <0.08%, and a viscosity of 1000-2000 mPa s at 23°C.

[0087] DMIPA N,N-dimethylisopropylamine, CAS 996-35-0

[0088] Mechanical Testing for Breaking Strength

[0089] The test specimens are produced using the “cold box” process and their bending strengths are determined at various times immediately after forming. The production of the test specimens is carried out in accordance with the technical standard VDG P73. For this purpose, the sand is loaded into a mixing vessel. The polyol component and the polyisocyanate component (Table 2) are weighed separately in the mixing vessel. Subsequently, the raw materials are mixed in a paddle mixer for 2 minutes to form the moulding mixture. The specimens are produced using a Laempe L1 coreshooting machine equipped with a liquid amine evaporator. Immediately after its production as described above, the moulding mixture is loaded into the machine shooting-head. The core-shooting parameters are as follows: shooting time of 4 seconds, post-shooting delay time of 4 seconds, and shooting pressure of 4.5 bar. For polymerization, the specimens are gassed for 30 seconds at a gassing pressure of 2.5 bar with dimethylisopropylamine (DMIPA) in a flow of dry air. The three-point bending strength (TPB) is measured using a Benetlab Allinone instrument at specific times (30 seconds, 1 hour, 24 hours, Table 2) after the end of gassing.

Claims

Claims1. Foundry binder system comprising a polyol component and an isocyanate component, wherein said isocyanate component has an isocyanate monomer content of less than 0.1 %.

2. Binder system according to claim 1 , wherein the isocyanate component has an active content of isocyanate-urethane nature of less than 80%, preferably between 48% and 24%, and more preferably between 48% and 39%.

3. Binder system according to claim 1 or 2, wherein said isocyanate component has a viscosity of between 10 and 1200 mPa s at 23°C, preferably of 50-600 mPa s at 23°C.

4. Binder system according to any one of claims 1 to 3, wherein said isocyanate component comprises organic diisocyanates selected from toluene diisocyanate (TDI), ethylene diisocyanate, propylene diisocyanate, diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate (pPDI), methylene-bis(4-cyclohexyl)isocyanate (CHDI), xylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate and mixtures thereof, preferably toluene diisocyanate (TDI).

5. Binder system according to any one of claims 1 to 4, wherein said polyol component is selected from the group comprising glycols, polyglycols, polyols, saccharide polyols, polyether polyols, polyester polyols, polyols from PET, polyols from cashew or cardanol oil, biopolyols, aminopolyols, phenolic polymers and oligomers of a benzyl ether nature, alkoxylated novolacs, resol resins, epoxy oxydrilated resins, phenoxy resins, alkyd resins and mixtures thereof, or their corresponding thiol compounds.

6. Binder system according to any one of claims 1 to 5, wherein said isocyanate component is obtained by dilution from a prepolymer, or polymeric adduct, by at leastone solvent with a prepolymer / adduct: solvent weight ratio in the range of 1 :4.4 to 1 :1.8, preferably in the range of 1 :2.6 to 1 :2.1.

7. Binder system according to claim 6, wherein said isocyanate component comprises toluene diisocyanate (TDI) having an initial isocyanate group (NCO) content of 10.0-10.8% which, after dilution with at least one solvent, is comprised between 10.3% and 4.0%.

8. Binder system according to claim 6 or 7, wherein at least one solvent is selected from the group comprising esters of saturated or unsaturated vegetable or animal fatty acids, vegetable oils, aliphatic esters, aromatic esters, cyclic ketones, isophorone, lactones, cyclic carbonates, silicic acid esters, alkanes, cycloalkanes, aromatic solvents and mixtures thereof, preferably esters of dicarboxylic acids, rapeseed oil methyl ester and mixtures thereof.

9. Use of the binder system according to any one of claims 1 to 8, for producing foundry cores and / or moulds.

10. Foundry cores and / or moulds comprising the binder systems according to any one of claims 1 to 8 and sand, and / or other refractory material.

11. Process for producing foundry cores and / or moulds comprising a step of producing a mixture of moulding materials comprising the binder systems according to any one of claims 1 to 8 together with silica sand and / or other granular refractory material, and a step of cross-linking said mixture of moulding materials through a gas stream containing a tertiary amine.

12. Process for producing foundry cores and / or moulds, wherein a binder system according to any one of claims 1 to 8, a catalyst and sand, and / or other refractory material are mixed together at room temperature.

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