DE102006037288B4 - Molding material mixture containing Cardol and / or Cardanol in foundry binders based on polyurethane, process for the preparation of a molded article and use thereof - Google Patents

Abstract

Molding material mixture for the production of moldings for the foundry industry, comprising at least: - a refractory molding material; and a polyurethane-based binder system which comprises a polyisocyanate component and a polyol component, the polyol component is formed from a benzyl ether resin and wherein the binder system contains at least a proportion of cardol and / or cardanol and / or their derivatives, wherein the derivatives on at least one double bond of the Side chain are derivatized, and the cardol and / or cardanol and / or derivatives thereof can also be incorporated in the benzyl ether resin / can.

Description

The invention relates to a molding material mixture for the production of moldings for the foundry industry, a method for producing a casting mold using the molding material mixture, a casting mold, and the use of the casting mold for metal casting.

Molds for the production of metal bodies are essentially produced in two versions. A first group are the so-called nuclei and forms. From these, the mold is assembled, which is essentially a negative mold of the casting to be produced, wherein cores serve to form cavities in the interior of the casting, while the forms represent the outer boundary. Often, only the inner cavities are imaged by cores, while the outer contour of the casting is represented by a green sand mold or a steel mold. A second group form hollow bodies, so-called feeders, which act as balancing reservoir. These take up liquid metal, whereby appropriate measures are taken to ensure that the metal remains in the liquid phase longer than the metal that is in the negative mold forming mold. If the metal solidifies in the negative mold, liquid metal can flow out of the compensation reservoir to compensate for the volume contraction that occurs when the metal solidifies.

Casting molds are made of a refractory material, such as quartz sand, whose grains are connected after molding of the mold by a suitable binder to ensure sufficient mechanical strength of the mold. For the production of molds so you use a refractory molding material, which is mixed with a suitable binder. The molding material mixture obtained from molding material and binder is preferably present in a free-flowing form, so that it can be filled into a suitable mold and compacted there. The binder produces a firm cohesion between the particles of the molding base material, so that the casting mold obtains the required mechanical stability.

For the production of casting molds both organic and inorganic binders can be used, the curing of which can be effected by cold or hot processes. Cold processes are processes which are carried out essentially at room temperature without heating the molding material mixture. The curing is usually carried out by a chemical reaction, which can be triggered, for example, by passing a gaseous catalyst through the molding material mixture to be cured, or by adding a liquid catalyst to the molding material mixture. In hot processes, after molding, the molding material mixture is heated to a temperature high enough to expel, for example, the solvent contained in the binder or to initiate a chemical reaction by which the binder is cured by crosslinking.

At present, for the production of casting molds, organic binders, e.g. Polyurethane, furan resin or epoxy-acrylate binders used in which the curing of the binder is carried out by adding a catalyst. Polyurethanes based on polyurethanes are generally composed of two components, wherein a first component consists of a phenolic resin and the second component of a polyisocyanate. These two components are mixed with the molding base material and the molding mixture is brought into a mold by ramming, blowing or another method, compacted and then cured. Depending on the method in which the catalyst is introduced into the molding material mixture, a distinction is made between the "polyurethane no-bake process" and the "polyurethane cold-box process". In the no-bake process, a liquid catalyst, generally a liquid tertiary amine, is introduced into the molding material mixture before it is shaped and cured. The conditions are chosen so that the ready-made molding material mixture has a sufficiently long processing time within which the shaping can be carried out. The polymerization must be correspondingly slow, so that not already in the storage tanks or supply lines, a curing of the molding material mixture. On the other hand, the curing should not be too slow to achieve a sufficiently high throughput in the production of molds. In the cold-box process, the molding material mixture is first brought into a mold without catalyst. Through the molding material mixture, a gaseous tertiary amine is then passed, which may optionally be mixed with an inert carrier gas. On contact with the gaseous catalyst, the binder binds very quickly, so that a high throughput in the production of molds is achieved.

In the US 3,409,579 there is described a binder composition comprising a mixture of a resin component, a curing component and a curing agent. The resin component comprises a phenolic resin obtained by condensing a phenol and an aldehyde. The Phenol resin is dissolved in an organic solvent. The curing component comprises a liquid polyisocyanate having at least two isocyanate groups. As a hardening agent, the binder comprises a tertiary amine. For the production of molded articles, first the phenolic resin component and the polyisocyanate component are mixed with a refractory molding base material. The molding material mixture is subsequently brought into a mold. To cure the molding material mixture is passed through these normally at room temperature, the gaseous curing agent, for example trimethylamine, dimethylethylamine, dimethylisopropylamine or triethylamine. For better vaporizability, the tertiary amine can be heated. After curing, the mold can be removed.

In the US 3,676,392 there is described a resin composition comprising a phenol resin component dissolved in organic solvents, a curing agent component, and a curing catalyst. The hardener component used is a liquid polyisocyanate comprising at least two isocyanate groups. The polyisocyanate is used in an amount of 10 to 500% by weight based on the weight of the resin. As the curing catalyst, a base having a pK _b in the range of about 7 to about 11 and used in an amount of 0.01 to 10% by weight based on the resin is used.

For the production of molds, phenolic resin, polyisocyanate and curing catalyst are mixed with the refractory molding base. This can be done in such a way that the mold base material is first coated with a component of the binder and then the other component is added. The curing catalyst is added to one of the components.

in welcher A, B und C Wasserstoff, Halogen oder Kohlenwasserstoffreste, die auch über ein Sauerstoffatom an den Phenylring gebunden sein können, bedeuten, mit einem Aldehyd der allgemeinen Formel R'CHO, in welcher R' für ein Wasserstoffatom oder einen Kohlenwasserstoffrest mit 1 bis 8 Kohlenstoffatomen steht, bei einem molaren Verhältnis von Aldehyd zu Phenol von größer als eins in flüssiger Phase bei wasserfreien Bedingungen und Temperaturen von unterhalb 130 °C in Gegenwart katalytisch wirksamer Mengen eines im Reaktionsmedium löslichen zweiwertigen Metallsalzes umgesetzt. Bei der Umsetzung entsteht ein Gemisch aus Dimethylolverbindungen der folgenden Formeln:

in welchen R für Wasserstoff oder einen in meta-Stellung zur phenolischen OH-Gruppe angeordneten phenolischen Rest steht, sowie höher kondensierte Verbindungen der Formel:

in welcher R die oben angegebene Bedeutung aufweist, die Summe von m und n zumindest zwei ergibt und das Verhältnis m/n zumindest eins ergibt. Ferner steht X für eine endständige Gruppe, die ausgewählt ist aus Wasserstoff und einer Methylolgruppe, wobei das molare Verhältnis von endständigen Methylolgruppen zu endständigem Wasserstoff zumindest eins betragt. Zur Herstellung des Phenolharzes können unsubstituiertes Phenol, wie auch substituierte Phenole verwendet werden.Both in the in the US 3,409,579 described cold box method as well as in the US 3,676,392 phenol resins are used as polyols obtained by condensation of phenol with aldehydes, preferably formaldehyde, in the liquid phase at temperatures up to about 130 ° C in the presence of catalytic amounts of metal ions described no-bake method. The preparation of such phenolic resins is for example in the US 3,485,797 described. Phenols of the general formula are used for the preparation of the phenolic resins

in which A, B and C are hydrogen, halogen or hydrocarbon radicals which may also be bonded via an oxygen atom to the phenyl ring, with an aldehyde of the general formula R'CHO, in which R 'is a hydrogen atom or a hydrocarbon radical having 1 to 8 carbon atoms, reacted at a molar ratio of aldehyde to phenol of greater than one in the liquid phase at anhydrous conditions and temperatures below 130 ° C in the presence of catalytically effective amounts of a soluble in the reaction medium divalent metal salt. In the reaction, a mixture of dimethylol compounds of the following formulas is formed:

in which R stands for hydrogen or a phenolic radical arranged in the meta position to the phenolic OH group, as well as higher condensed compounds of the formula:

in which R has the meaning given above, the sum of m and n is at least two and the ratio m / n is at least one. Further, X is a terminal group selected from hydrogen and a methylol group, wherein the molar ratio of terminal methylol groups to terminal hydrogen is at least one. Unsubstituted phenol as well as substituted phenols may be used to prepare the phenolic resin.

In the WO 85/05580 there is described a binder composition comprising a resin component, a polyisocyanate as a hardener component, and an amine as. Curing component includes. The resin component is formed by a phenol resin obtained by condensing a phenol component and an aldehyde component. At least one mole percent of the phenolic component is formed by an alkyl-substituted phenol, preferably o-cresol or p-nonylphenol.

As a further reaction component, aliphatic monoalcohols can be added in the preparation of the phenolic resin. So will in the EP 0 177 871 describes a polyurethane binder containing as polyhydroxy a phenolic resole resin which is modified with alkoxy groups. The resole resin comprises at least one alkoxymethylene group per six phenolic cores. The alkoxymethylene groups are introduced by adding monohydric primary or secondary alcohols during synthesis of the resole resin. The alcohols comprise one to 8 carbon atoms, with methanol being particularly preferred. The alkoxymethylene groups have the general formula - (CH ₂ O) _n R where R is the alkyl group of the alcohol and n is a small integer. The alkoxymethylene groups are located ortho or para to the phenolic hydroxy group. By alkoxylation, the binder systems are to obtain increased thermal stability.

In order to be able to apply the polyhydroxy component and the polyisocyanate component in a thin film uniformly on the grains of the molding material, the components are diluted with solvents. In order to achieve a compatibility of the components, usually aromatic solvents are used, but some of which can develop a harmful effect. In the EP 0 771 599 A1 polyurethane-based binder systems containing methyl esters of higher fatty acids as solvents are described. Particularly suitable is Rapeseed oil methyl ester used as the sole solvent. A further advantage is that molds which are produced using this binder system can be removed particularly easily from the mold.

Cashew nut oil is obtained from cashew nut shell extraction and is composed in its natural form of anacardic acid and cardol in a weight ratio of about 9: 1. Both components have a straight hydrocarbon chain with fifteen carbon atoms, in which there are predominantly simple and conjugated double bonds. Technical cashew nut shell oil is obtained from the natural product by heating under acidic conditions. Decarboxylation of the anacardic acid results in a mixture of Cardanol and Cardol, also known as CNSL (Cashew Nutshell Liquid). In the thermal treatment, oligomers of these compounds, which remain in the distillation bottoms and can be isolated from this arise. Cashew nut oil and its derivatives are used in a number of technical manufacturing processes.

In the DE 42 33 802 A1 For example, there is described a rubber composition for the production of automotive tires, which comprises 100 parts by weight of a rubber component comprising one or more of natural rubber, polyisoprene rubber, polybutadiene rubber and styrene-butadiene rubber, 50 to 70 parts by weight of carbon black average particle size of less than 40 nm, 5 to 20 parts by weight of novolak-modified phenolic resin, 0.5 to 2 parts by weight of hexamethylenetetramine and 5 to 20 parts by weight of a polymeric cardanol having a viscosity of 20,000 to 50,000 mPas , The rubber composition has a relatively low stiffness before vulcanization and a relatively high modulus of elasticity after vulcanization, making it particularly suitable for use as a tire bead filler.

In the DE 39 01 930 A1 describes a process for the preparation of novolaks, wherein phenols or mixtures of phenols are reacted with oxo compounds by condensation of the reactants in a water-poor medium in homogeneous phase. The reaction takes place at temperatures above 110 ° C. and preferably at atmospheric pressure in the presence of water-immiscible and / or only partially water-miscible inert organic solvents, such as toluene, xylene, diethylbenzene or alcohols, such as butanol. As a catalyst, strong mineral acids can be used, such as sulfuric acid. The water added, for example, in the form of an aqueous formaldehyde solution and the water formed during the condensation is distilled off continuously during the reaction, preferably by azeotropic distillation with recycling of the entraining agent. The work-up of the reaction solution, which consists essentially of novolak, unreacted phenol and entrainer, is carried out by vacuum distillation, the distillation conditions determining the residual content of phenol.

As oxo compounds aldehydes and ketones can be used, which form condensation products with phenols. Suitable aldehydes are, for example, formaldehyde, acetaldehyde and their homologs or isomers having up to 18 carbon atoms per molecule. As the phenolic component, it is possible to use all phenolic compounds which have at least one reactive hydrogen atom on the aromatic nucleus and are at least monofunctional in their reactivity with aldehydes. Preferably phenol itself, the different cresol and xylene isomers, as well as p-resp. used o-substituted alkylphenols having up to 18 carbon atoms in the side chain. It is also possible to use unsaturated phenols, such as o- or p-vinylphenol, and the C ₁₅ -unsaturated alkenylphenols obtainable by distillation of cashew nut shell oil. The novolaks obtainable by the process can be used, for example, as reinforcing resins for rubber and elastomers. For this they are incorporated together or separately with crosslinking agents, such as hexamethylenetetramine and / or aminoplasts and / or resoles, optionally after a preliminary reaction, in the not yet vulcanized rubber or elastomer mixture. Further fields of use include friction linings, impregnating agents for organic and inorganic fibers, coatings, coatings and lacquers, and a use as a binder for comminuted, preferably inorganic materials.

In the DE 100 04 427 describes a process for the preparation of polyurethanes using a Cashew nut shell oil whose double bonds have been previously at least partially saturated, for example with sulfur or peroxides. The saturation is carried out only to the extent that no excessive increase in the viscosity occurs, that is, a good liquid product is obtained, which can be easily mixed with an isocyanate. The reaction with the polyisocyanate can be carried out with the cashew nut shell oil alone or with a mixture of the saturated cashew nut shell oil and other polyols and / or soybean oil, wherein the content of the cashew nut shell oil is at least 30, in particular at least 60% by weight. The polyisocyanate used is preferably diisocyanates, for example diphenylmethane-4,4'-diisocyanate (MDI).

In the DE 101 58 693 A1 there is described a granular material coated with a resin obtained by reacting an isocyanate component with a polyol component. The polyol component contains at least one compound selected from cardol, cardanol, as well as derivatives or oligomers of these compounds. The coating is permeable to water, but insoluble in water. More preferably, fertilizers are coated with the resin so as to achieve release of the fertilizer into the soil over an extended period of time. As the polyhydroxy component, Cardol and Cardanol are used by themselves or in the form of oligomers which can be obtained, for example, by reaction with formaldehyde or acid, in particular glyoxylic acid. The coating of the granules takes place for example in a rotating drum, in which the material to be coated is kept in motion during the entire coating process.

The following documents are also known from the prior art: WO 2006/010777 A1 and EP 0002499 B1 known.

The binder systems hitherto used for the production of cores and molds still contain more or less large amounts of unreacted phenol or formaldehyde. Since these substances are harmful to health, one tries to lower the content of the resins of these toxic monomers as far as possible. In many cases, this is achieved by changing the reaction procedure, for example by prolonged condensation and / or distillation times. However, these measures also entail considerable disadvantages. Thus, with a longer condensation time, the viscosity of the resins increases and their storage stability decreases. Prolonged vacuum distillation degrades the yield and valuable monomers are distilled off uselessly.

In order to avoid casting defects, high demands are placed on the strength and dimensional stability of the mold or cores. The moldings should remain dimensionally stable, especially at higher temperatures. Such higher temperatures are achieved, for example, during drying of a coating of a refractory material which has been applied to the shaped body. Likewise, the molding should remain stable during the casting process and be able to withstand the stresses caused by the inflowing liquid metal.

The invention was therefore based on the object to provide a molding material mixture from which moldings can be produced which have a high stability even under thermal stress, and which preferably has a very low content of harmful residual monomers.

This object is achieved with a molding material mixture having the features of patent claim 1. Advantageous embodiments of the molding material mixture are the subject of the dependent claims.

It has been found that by adding cardol and / or cardanol and / or derivatives thereof, derivatized on at least one double bond of the side chain, it is possible to obtain molded articles for the foundry industry which have high thermal stability. As a further advantage, the content of monomers which are still contained in the polyol component, in particular phenol and formaldehyde, can be significantly reduced. In the processing of the molding material mixture and in particular during the casting process, therefore, relatively small amounts of monomers are liberated in comparison with molding material mixtures of the prior art. The monomers often have a harmful effect, so that the reduced amount of released monomers and the burden of harmful substances in the workplace in the foundry can be reduced.

For the purposes of the invention, cashew nut shell oil is understood as meaning both the oil obtained from seed casks of the cashew tree, which comprises about 90% anacardic acid and about 10% cardol, and the technical cashew nut shell oil which is obtained from the natural product by heat treatment acidic environment, and contains as main ingredients Cardanol and Cardol.

Suitable components of the binder are cardol and / or cardanol, as well as mixtures thereof, such as those which remain in the bottoms during the distillation of cashew nut shell oil. These compounds can also be used in technical quality. The mixture of essentially cardanol and cardol, which is also known as cashew nutshell liquid (CNSL), formed during the distillation of cashew nut shell oil is preferably used. The double bonds of cardanol and cardol contained in the side chain may be partially or fully reacted with hydroxyl groups, epoxide groups, halogens, acid anhydrides, diclyclopentadiene or hydrogen. These groups can in turn be reacted with nucleophiles. Such compounds are derivatives of Cardol or Cardanols called. In polyvalent derivatives, the phenolic OH groups may also be completely or partially derivatized, for example by addition of ethylene oxide or propylene oxide units. These derivatives can also be used according to the invention in the molding material mixture.

Cardol and / or cardanol or the above-described derivatives may be present as a separate component in the binder. These components act as a reactive solvent, which reacts with the curing of the binder in the resulting crosslinked polymer. In this embodiment of the molding material mixture according to the invention in particular a high stability of the molded body is achieved at elevated temperature. Thus, test bars which have been produced from the molding material mixture according to the invention show less deflection under thermal stress than test bars which have been produced with an analogous binder, but no cardol and / or cardanol and / or their derivatives have been added to the binder.

• - einen feuerfesten Formgrundstoff; und
• - ein Bindemittelsystem auf Polyurethanbasis, welches eine Polyisocyanatkomponente sowie eine Polyolkomponente umfasst,

wobei das Bindemittelsystem zumindest einen Anteil an zumindest einem Bestandteil der Gruppe bestehend aus Cardol, Cardanol und den oben beschriebenen Derivaten enthält.The molding material mixture according to the invention for the production of cores and molds for the foundry industry comprises at least:

• a refractory base molding material; and
• a polyurethane-based binder system comprising a polyisocyanate component and a polyol component,

wherein the binder system contains at least a portion of at least one member of the group consisting of cardol, cardanol, and the derivatives described above.

As a refractory molding base material, all refractory materials that are customary for the production of moldings for the foundry industry can be used per se. Examples of suitable refractory mold bases are quartz sand, zircon sand, olivine sand, aluminum silicate sand and chrome ore sand or mixtures thereof. Preferably, quartz sand is used. The refractory base molding material should have a sufficient particle size so that the molded article produced from the molding material mixture has a sufficiently high porosity to allow escape of volatile compounds during the casting process. Preferably, at least 80% by weight, particularly preferably at least 90% by weight, of the refractory molding base material has a particle size ≦ 290 μm. The average particle size of the refractory base molding material should preferably be between 100 and 350 μm.

The binder contains as essential components a polyol component and a polyisocyanate component.

The polyisocyanate component of the binder system may comprise an aliphatic, cycloaliphatic or aromatic isocyanate. The polyisocyanate preferably contains at least two isocyanate groups, preferably 2 to 5 isocyanate groups per molecule. Depending on the desired properties, it is also possible to use mixtures of isocyanates. The isocyanates used can consist of mixtures of monomers, oligomers and polymers and are therefore referred to below as polyisocyanates.

The polyisocyanate component per se can be any polyisocyanate which is customary in polyurethane binders for molding mixtures for the foundry industry. Suitable polyisocyanates include aliphatic polyisocyanates, e.g. Hexamethylene diisocyanate, alicyclic polyisocyanates, e.g. 4,4'-dicyclohexylmethane diisocyanate, and dimethyl derivatives thereof. Examples of suitable aromatic polyisocyanates are toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylylene diisocyanate and methyl derivatives thereof, diphenylmethane-4,4'-diisocyanate and polymethylene-polyphenyl polyisocyanates.

Although in principle all conventional polyisocyanates can react with the phenolic resin to form a crosslinked polymer structure, it is preferred to use aromatic polyisocyanates, more preferably polymethylene-polyphenyl polyisocyanates, e.g. the commercially available mixtures of diphenylmethane-4,4'-diisocyanate, its isomers and higher homologs.

The polyisocyanates can be used both in bulk or dissolved in an inert or reactive solvent. The polyisocyanates are preferably used in dilute form in order to be able to coat the grains of the refractory molding base material better with a thin film of the binder because of the lower viscosity of the solution.

The polyisocyanates or their solutions in organic solvents are used in sufficient concentrations to effect curing of the polyol component, usually in a range of from 10 to 500 weight percent, based on the weight of the polyol component. From 20 to 300% by weight, based on the same base, are preferably used. Liquid polyisocyanates can be used in undiluted form while solid or viscous polyisocyanates are dissolved in organic solvents. Up to 80% by weight of the isocyanate component may consist of solvents.

As solvents for polyisocyanates, preference is given to using high-boiling aromatic and aliphatic hydrocarbons and high-boiling fatty acid esters or mixtures of the substances mentioned. Suitable aromatic solvents are alkyl-substituted benzenes, alkyl-substituted naphthalenes, and mixtures thereof. The alkyl substituents preferably have 1 to 6 carbon atoms. The boiling point of the solvent or solvent mixture is preferably at least 150 ° C. Examples of suitable solvents are toluene, xylene, ethylbenzene and mixtures thereof, as well as high-boiling aromatic hydrocarbon fractions.

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

The polyol component contains at least benzyl ether resins. The polyol component contains at least two hydroxyl groups which can react with the isocyanate groups of the polyisocyanate component in order to achieve cross-linking of the binder during curing and thereby improved strength of the cured molded article.

The polyol component is preferably used liquid or dissolved in organic solvents in order to allow a homogeneous distribution of the binder on the refractory base molding material. The polyol component is preferably used in anhydrous form because the reaction of the isocyanate component with water is an undesirable side reaction. Non-aqueous or anhydrous in this context means a water content of the polyol component of preferably less than 5 wt .-%, preferably less than 2 wt .-%, mean.

By "addition products" is meant reaction products in which an organic group substitutes at least one hydrogen on a previously unsubstituted phenol or condensation product. By "condensation products" is meant reaction products having two or more phenolic rings.

Condensation reactions of phenols with aldehydes result in phenolic resins, which are subdivided into different product classes as a function of the proportions of the starting materials, the reaction conditions and the catalysts used:

Novolacs are soluble, meltable, non-self-curing, and shelf-stable oligomers having a molecular weight in the range of about 500-5,000 g / mol. They are obtained in the condensation of aldehyde and phenol in a molar ratio of 1:> 1 in the presence of acidic catalysts. Novolacs are phenol resins free of methylol groups in which the phenyl nuclei are linked via methylene bridges. They may be cured at elevated temperature with the addition of curing agents, such as formaldehyde donating agents (preferably hexylmethylenetetramine). Novolacs are not according to the invention.

Suitable catalysts for the preparation of benzylic ether resins are salts of divalent ions of metals such as Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca and Ba. Preferably, zinc acetate is used. The amount used is not critical. Typical amounts of metal catalyst are 0.02 to 0.3 wt .-%, preferably 0.02 to 0.15 wt .-%, based on the total amount of phenol and aldehyde.

For the preparation of the benzyl ether resins, all conventionally used phenols are suitable. In addition to unsubstituted phenol, substituted phenols or mixtures thereof can be used. The phenolic compounds are unsubstituted either in both ortho positions or in an ortho and in the para position to allow polymerization. The remaining ring carbon atoms may be substituted. The choice of the substituent is not particularly limited so long as the substituent does not adversely affect the polymerization of the phenol and the aldehyde. Examples of substituted phenols are alkyl-substituted phenols, alkoxy-substituted phenols and aryloxy-substituted phenols.

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

Particularly preferred is phenol itself. Also higher condensed phenols, such as bisphenol A, are suitable. In addition, polyhydric phenols having more than one phenolic hydroxyl group are also suitable. Preferred polyhydric phenols have 2 to 4 phenolic hydroxyl groups. Specific examples of suitable polyhydric phenols are catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, 2,5-dimethylresorcinol, 4,5-dimethylresorcinol, 5-methylresorcinol or 5-ethylresorcinol.

It is also possible to use mixtures of different mono- and / or polyhydric and / or substituted and / or condensed phenol components for the preparation of the polyol component.

zur Herstellung der Phenolharz-Komponente verwendet, wobei A, B und C unabhängig voneinander aus einem Wasserstoffatom, einem verzweigten oder unverzweigten Alkylrest (der beispielsweise 1 bis 26, vorzugsweise 1 bis 15, Kohlenstoffatome aufweisen kann), einem verzweigten oder unverzweigten Alkoxyrest (der beispielsweise 1 bis 26, vorzugsweise 1 bis 15, Kohlenstoffatome aufweisen kann), einem verzweigten oder unverzweigten Alkenoxyrest (der beispielsweise 1 bis 26, vorzugsweise 1 bis 15, Kohlenstoffatome aufweisen kann), einen Aryl- oder Alkylarylrest, wie beispielsweise Bisphenyle, ausgewählt sind.In one embodiment, phenols of general formula I:

used for the preparation of the phenolic resin component, wherein A, B and C independently of one another from a hydrogen atom, a branched or unbranched alkyl radical (which may have, for example 1 to 26, preferably 1 to 15, carbon atoms), a branched or unbranched alkoxy (for example 1 to 26, preferably 1 to 15, carbon atoms), a branched or unbranched alkenoxy group (which may, for example, have 1 to 26, preferably 1 to 15, carbon atoms), an aryl or alkylaryl group, such as bisphenols, are selected.

Suitable aldehydes for the preparation of the phenolic resin component are aldehydes of the formula R-CHO wherein R is a hydrogen atom or a carbon atom radical having preferably 1 to 8, particularly preferably 1 to 3 carbon atoms. Specific examples are formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and benzaldehyde. Particularly preferably, formaldehyde is used, either in its aqueous form, as paraformaldehyde or trioxane.

In order to obtain the benzylic ether resins as phenolic resins, an at least equivalent number of moles of aldehyde, based on the number of moles of the phenol component, is used. The molar ratio of aldehyde: phenol is preferably 1: 1.0 to 2.5: 1, more preferably 1.1: 1 to 2.2: 1, particularly preferably 1.2: 1 to 2.0: 1.

The preparation of the phenolic resin component is carried out by methods known in the art. In this case, as already described in the discussion of the prior art, the phenol and the aldehyde or ketone under substantially anhydrous conditions in the presence of a divalent metal ion at temperatures of preferably less than 130 ° C implemented. The resulting water is distilled off. For this purpose, the reaction mixture, a suitable entraining agent may be added, for example, toluene or xylene, or the distillation are carried out at reduced pressure.

For the binder of the molding material mixture according to the invention, the phenol component is reacted with an aldehyde to give benzyl ether resins. The reaction with a primary or secondary aliphatic alcohol to form an alkoxy-modified phenolic resin in the one-stage or two-stage process ( EP-B-0 177 871 and EP 1 137 500 A1) is also possible. In the one-step process, the phenol, the aldehyde or the ketone and the alcohol are reacted in the presence of a suitable catalyst. In the two-step process, an unmodified resin is first prepared, which is subsequently reacted with an alcohol. When using alkoxy-modified phenolic resins, there is no limitation on the molar ratio per se, but the alcohol component is preferably used in a molar ratio of alcohol: phenol of less than 0.25 so that less than 25% of the hydroxymethyl groups are etherified. Suitable alcohols are primary and secondary aliphatic alcohols having one hydroxy group and 1 to 10 carbon atoms. Suitable primary and secondary alcohols are, for example, methanol, ethanol, propanol, n-butanol and n-hexanol. Particularly preferred are methanol and n-butanol. The use of novolaks as phenolic resin components is also possible.

The phenolic resin is preferably selected so that crosslinking with the polyisocyanate component is possible. For the construction of a network, phenolic resins comprising molecules having at least two hydroxyl groups per molecule are particularly suitable.

The phenolic resin component of the binder system is preferably used as a solution in an organic solvent or a combination of organic solvents. Solvents may be required to keep the components of the binder in a sufficiently low viscosity state. This is u.a. necessary to obtain a uniform wetting of the refractory base molding material and its flowability.

All solvents which are conventionally used in binder systems for foundry technology can be used in the binder system of the molding material mixture according to the invention. Suitable solvents for the phenolic resin component are, for example, oxygen-rich, polar, organic solvents and nonpolar, aprotic solvents, such as high-boiling aromatic hydrocarbons (in particular in the form of mixtures) having a boiling point of more than 150 ° C. Particularly suitable are dicarboxylic acid esters, glycol ether esters, glycol diesters, glycol diethers, cyclic ketones, cyclic esters or cyclic carbonates. Dicarboxylic acid esters, cyclic ketones and cyclic carbonates are preferably used. Dicarboxylic acid esters have the formula R ^a OOC-R ^b -COOR ^a , wherein the radicals R ^{a are} each independently an alkyl group having 1 to 12, preferably 1 to 6, carbon atoms and R ^{b is} an alkylene group having 1 to 12, preferably 1 to 6, carbon atoms. Examples are dimethyl esters of carboxylic acids having 4 to 10 carbon atoms which are available, for example, under the name "Dibasic Ester" (DBE) from DuPont. Glycol ether esters are compounds of the formula R ^c -OR ^d -OOCR ^e , where R ^{c is} an alkyl group having 1 to 4 carbon atoms, R ^{d is} an ethylene group, a propylene group or an oligomer of ethylene oxide or propylene oxide and R ^{e is} an alkyl group having 1 to 3 carbon atoms is; preferred are glycol ether acetates (eg butyl glycol acetate). Glycol diesters accordingly have the general formula R ^e COO-R ^d -OOCR ^e where R ^d and R ^{e are} as defined above and the radicals R ^{e are} each independently selected; preferred are glycol diacetates (eg, propylene glycol diacetate). Glycol diethers can be characterized by the formula R ^c -OR ^d -OR ^c wherein R ^c and R ^{d are} as defined above and the radicals R ^{c are} each independently selected (eg, dipropylene glycol dimethyl ether). Cyclic ketones, cyclic esters and cyclic carbonates of 4 to 5 carbon atoms are also suitable (eg propylene carbonate). The alkyl and alkylene groups may each be branched or unbranched. Also esters of long-chain fatty acids, as in the EP-A-1 137 500 described, can be used. Suitable fatty acids are, for example, having 8 to 22 carbon atoms, which are esterified with an aliphatic alcohol. Usually, fatty acids of natural origin, such as tall oil, rapeseed oil, sunflower oil, germ oil and coconut oil, are used. Instead of natural oils and fats, it is also possible to use individual fatty acids, such as palmitic acid or oleic acid. The aliphatic alcohols used are preferably primary alcohols having 1 to 12 carbon atoms, particularly preferably 1 to 10 carbon atoms, particularly preferably 4 to 10 carbon atoms, with methanol and n-butanol being particularly preferred. The "symmetrical esters" described in EP-B-0 295 262, in which both the acid radical and the alcohol radical have a number of carbon atoms (about 6 to 13 carbon atoms) in the same range, have also proved useful.

Esters of long-chain fatty acids, a mixture of dimethyl esters of C ₄ -C ₆ -dicarboxylic acids (DBE), symmetrical esters and cyclic ketones are preferably used in the present invention in addition to high-boiling hydrocarbons.

The cardol and / or the cardanol and / or derivatives thereof preferably form at least a portion of the polyol component. In this embodiment, Cardol and / or cardanol and / or their derivatives are added during the synthesis of the polyol component so that they are incorporated into the polyol component during synthesis. The synthesis of the polyol component is carried out in a known manner, wherein Cardol and / or cardanol and / or their derivatives can already be added to the reaction mixture at the beginning of the synthesis or at a later time of the synthesis.

The synthesis of the polyol component is carried out in the manner described above for the preparation of the phenolic resin, but in addition to the phenolic component cardol and / or cardanol and / or derivatives thereof is added as a further component.

The proportion of cardol and / or cardanol and / or derivatives thereof in the phenolic component is preferably 0.5 to 20% by weight, more preferably 0.75 to 15% by weight, particularly preferably 1 to 10% by weight. ,

Cardol and / or cardanol and / or their derivatives can be added to the reaction mixture at any time during the synthesis. Preferably, the addition takes place already at the beginning of the synthesis.

The proportion of solvent on the binder system is preferably chosen as low as possible. The solvent content of the polyol component is therefore preferably chosen to be less than 50% by weight, particularly preferably less than 40% by weight. The dynamic viscosity of the polyol component, which can be determined, for example, by the Brookfield spin-spindle method, is preferably less than 1000 mPas, more preferably less than 800 mPas, and particularly preferably less than 600 mPas.

Cardol and / or cardanol and / or their derivatives can also be added to the isocyanate component, wherein they can also react with a part of the isocyanate groups.

The proportion of the binder system (polyol and isocyanate component), based on the weight of the refractory molding material, is preferably between 0.5 and 10 wt .-%, preferably chosen between 0.8 and 7 wt .-%.

In addition to the constituents already mentioned, the binder systems may contain conventional additives, eg silanes ( EP-A-1137500 ) or internal release agents, eg fatty alcohols (EP-B-0 182 809), drying oils ( US-A-4,268,425 ) or complexing agent ( WO 95/03903 ) or mixtures thereof.

Suitable silanes are, for example, aminosilanes, epoxysilanes, mercaptosilanes, hydroxysilanes and ureidosilanes, such as γ-hydroxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane.

Suitable release agents are, in particular, the fatty acid esters already described above, the butyl ester of oleic acid and tall oil fatty acid and the mixed octyl / decyl ester of tall oil fatty acid being particularly preferred.

For the preparation of the molding material mixture, the components of the binder system can first be combined and then added to the refractory molding material. However, it is also possible to add the components of the binder simultaneously or sequentially to the refractory base molding material. To obtain a uniform mixture of the components of the molding material mixture, conventional methods can be used. In addition, the molding material mixture may optionally contain other conventional ingredients such as iron oxide, ground flax fibers, wood flour granules, pitch and refractory flours.

• - Bereitstellen der oben beschriebenen Formstoffmischung;
• - Ausformen der Formstoffmischung zu einem Formkörper;
• - Aushärten des Formkorpers durch Zugabe eines Aushärtungskatalysators.

As a further subject matter, the invention relates to a process for producing a shaped body, comprising the steps:

• - Providing the molding material mixture described above;
• - Forming the molding material mixture into a shaped body;
• - Curing the Formkorpers by adding a curing catalyst.

For the production of the molded article, the binder is first mixed with the refractory molding base material to form a molding material mixture as described above. If the molding is to be produced by the PU-No-Bake process, a suitable catalyst can also already be added to the molding material mixture. For this purpose, liquid amines are preferably added to the molding material mixture. These amines preferably have a pK _B value of 4 to 11. Examples of suitable catalysts are 4-alkylpyridines, wherein the alkyl group comprises 1 to 4 carbon atoms, isoquinoline, arylpyridines, such as phenylpyridine, pyridine, Acridine, 2-methoxypyridine, pyridazine, 3-chloropyridine, quinoline, N-methylimidazole, 4,4'-dipyridine, phenylpropylpyridine, 1-methylbenzimidazole, 1,4-thiazine, N, N-dimethylbenzylamine, triethylamine, tribenzylamine, N, N Dimethyl 1,3-propanediamine, N, N-dimethylethanolamine, and triethanolamine. The catalyst may optionally be diluted with an inert solvent, for example an aromatic hydrocarbon. The amount of catalyst added is selected in the range of 0.5 to 15% by weight based on the weight of the phenolic resin.

The molding material mixture is then introduced by conventional means into a mold and compacted there. The shaped molding material mixture is then cured to a shaped body. When curing, the shaped body should preferably retain its outer shape. According to a further preferred embodiment, the curing takes place according to the PU cold box method. For this purpose, a gaseous catalyst is passed through the molded molding material mixture. As catalyst, the usual catalysts in the field of cold-box process can be used. Particular preference is given to using amines as catalysts, in particular preferably dimethylethylamine, dimethyl-n-propylamine, dimethylisopropylamine, dimethyl-n-butylamine, triethylamine and trimethylamine in their gaseous form or as aerosol.

The molded article produced by the process may per se have any shape customary in the foundry industry. In a preferred embodiment, the shaped body is in the form of foundry molds or cores.

Furthermore, the invention relates to a shaped body, as can be obtained by the method described above. This is characterized by a high mechanical stability, especially at higher temperatures, and a low content of harmful residual monomers, whereby the development of smoke during metal casting can be reduced.

Furthermore, the invention relates to the use of this shaped body for metal casting.

The invention will be explained in more detail below with reference to preferred embodiments.

Example 1 (not according to the invention):

A reaction vessel equipped with reflux condenser, thermometer and stirrer is charged with 698.4 g of phenol, 302.6 g of paraformaldehyde (91%) and 0.35 g of zinc acetate dihydrate. With stirring, the temperature is increased to 105-115 ° C and held until a refractive index (25 ° C) of about 1.5590 is reached. Thereafter, the condenser is switched to distillation and the temperature within one hour to 124 - 126 ° C increases. At this temperature is distilled until reaching a refractive index (25 ° C) of about 1.5940. Thereafter, vacuum is applied and distilled under reduced pressure up to a refractive index (25 ° C) of about 1.600. The yield is about 85%.

Example 2 - 4 (according to the invention)

Example 1 is repeated, but after reaching a refractive index (25 ° C) of about 1.5590, the amount of CNSL (Palmer 1500-1, Palmer International, USA) indicated in Table 1 is added. The further synthesis is carried out as indicated in Example 1. Table 1: Amount of added CNSL Example 1* Example 2 ** Example 3 ** Example 4 ** CNSL (g) - 50 g 100 g 150 g P / F 1: 1,230 1: 1.203 1: 1.178 1: 1.153 *: not according to the invention **: according to the invention

The phenolic resins shown in Examples 1 to 4 were examined for their content of free phenol (gas chromatography) and free formaldehyde (titrimetric according to the hydroxylammonium chloride method). The values are listed in Table 2 and refer to the phenolic resin obtained. Table 2 also includes a value of "phenol (theor.)". This is calculated from the phenol content determined in Example 1 taking into account the dilution caused by the addition of CNSL. Table 2: Levels of free phenol and formaldehyde in the phenolic resin Ex. 1 * Ex. 2 ** Ex. 3 ** Ex. 4 ** Phenol (%) 14,30 12.90 11.40 9.80 Formaldehyde (%) 1.20 0.80 0.50 0.35 Phenol (theor.) (%) - 13.62 13,00 12.43 *: not according to the invention **: according to the invention

The values given in Table 2 for the content of residual monomers show that the content of free phenol in the resins decreases with increasing amount of added CNSL. Although an increase in the free phenol content would be expected due to the decreasing molar ratio of phenol: formaldehyde (P / F), the decrease in phenol content is even higher than the dilution effect (phenol theor.).

Examples 5 to 8, production and testing of molding material mixtures

Preparation of phenolic resin solutions

The phenolic resins obtained in Examples 1 to 4 are diluted as follows: 53.0% phenolic resin 7.8% isophorone 19.0% aromatic hydrocarbons; Solvesso ^® 100 (Exxon) 15.7% phthalate 4.0% Tallölbutylester; Forbiol ^® 102 (H); Arizona Chemicals 0.5% silane

Preparation of the polyisocyanate solution

As a polyisocyanate, a solution of 80% 4,4'-diphenylmethane diisocyanate (industrial MDI) in 20% Solvesso ^® was 100.

Production and testing of the molding material mixtures

In each case, 0.6 part by weight of phenolic resin solution and 0.6 part by weight of polyisocyanate solution are added to 100 parts by weight of quartz sand H32 (Quarzwerke Frechen) and mixed thoroughly in a laboratory mixer. With this mixture test specimens (Georg Fischer Biegel, VDG method according to leaflet P73) with the dimensions 22.36 × 22.36 × 220 mm prepared by gassing with triethylamine (2 s at 2 bar pressure, then 10 s rinsing cured with air).

The flexural strength of the specimens is tested with a bending strength tester (Georg Fischer company) immediately after their production and after 24 hours of storage.

To determine the dimensional stability under thermal stress, Georg Fischer bending bars measuring 22.36 × 11.38 × 220 mm are stored horizontally for 10 minutes in a 150 ° C. drying oven 10 minutes after their preparation and are provided with a 400 mm centrifuge in their center g loaded heavy train weight. After 30 minutes, the test bars are removed from the oven and stored without weight for 60 minutes at room temperature. Then the deflection is measured. The values determined are given in Table 3. Table 3: Flexural strength and dimensional stability of test bars example 5 * 6 ** 7 ** 8th** Phenolic resin (Ex.) 1 2 3 4 Flexural strength (N / cm ² ) immediately 160 165 150 145 after 24 h 430 410 420 390 Deflection (mm) 1.85 0.70 0, 64 0.61 *: not according to the invention **: according to the invention

The test bars prepared with the phenolic resin of Examples 2 to 4 have sufficient strength. Under temperature stress, the test bars produced with the phenolic resin of Examples 2 to 4 are less resistant than the test bars prepared with the phenolic resin of Example 1.

Examples 9 to 12: Use of CNSL as Reactive Solvent

From the phenolic resin obtained in Example 1, the phenolic resin solutions shown in Table 4 were prepared. For the phenolic resin solution used in Example 10, the CNSL was added at the expense of the phenolic resin. For the phenolic resin solutions used in Examples 11 and 12, the CNSL was added at the expense of the solvent. Table 4: Preparation of phenolic resin solutions example 9 * 10 ** 11 ** 12 ** phenolic resin 53,00 48,00 53,00 53,00 CNSL - 5.00 5.00 10.00 isophorone 7.80 7.80 6.96 6.12 Solvesso 100 (H) 19,00 19,00 16.96 14.91 phthalate 15.70 15.70 14.00 12.32 Forbiol 102 (H) 4.00 4.00 3.85 3.15 silane 0.50 0.50 0.50 0.50 *: not according to the invention **: according to the invention

From the phenolic resins prepared in Examples 9 to 12, test bars were prepared analogously to Examples 5 to 8 and examined for their bending strength and dimensional stability. The results are summarized in Table 5. Table 5: Flexural strength and dimensional stability of test bars example 9 * 10 ** 11 ** 12 ** Flexural strength (N / cm ² ) immediately 160 110 145 165 after 24 h 430 355 395 400 Deflection (mm) 1.85 1.75 1.55 1.35 *: not according to the invention **: according to the invention

If a part of the phenolic resin is replaced by CNSL (Example 10), the bending strengths are reduced. However, the thermal stability of the test bar remains intact.

Replacing part of the solvent mixture with CNSL (Example 11 and 12) improves the dimensional stability of the test bars under thermal stress.

Claims (14)

Molding material mixture for the production of moldings for the foundry industry, comprising at least a refractory base molding material; and a polyurethane-based binder system which comprises a polyisocyanate component and a polyol component, the polyol component is formed by a benzyl ether resin and wherein the binder system contains at least a proportion of cardol and / or cardanol and / or their derivatives, wherein the derivatives are present on at least one double bond of the side chain are derivatized, and the cardol and / or cardanol and / or derivatives thereof may also be incorporated into the benzyl ether resin. Molding material mixture after Claim 1 , characterized in that the cardol and / or cardanol and / or derivatives thereof form / form at least a portion of the polyol component. Molding material mixture according to one of the preceding claims, characterized in that the cardol and / or cardanol and / or derivatives thereof and derivatives thereof, at least a portion of the isocyanate component forms / form. Molding material mixture according to one of the preceding claims, characterized in that the benzyl ether resin is formed by condensation of a phenolic component and an oxo component, wherein the cardol and / or cardanol and / or derivatives thereof forms at least a portion of the phenolic component. Molding material mixture according to one of the preceding claims, characterized in that the proportion of cardol and / or cardanol and / or derivatives thereof in the phenolic component between 5 and 20 wt .-%, preferably between 0.5 and 15 wt .-%, selected is. Molding material mixture according to one of the preceding claims, characterized in that the water content of the polyol component is less than 5 wt.%, Preferably less than 2 wt.%, Is. Molding material mixture according to one of the preceding claims, characterized in that the isocyanate component is an aliphatic, aromatic or heterocyclic isocyanate having at least two isocyanate groups per molecule or its oligomers or polymers. Molding material mixture according to one of the preceding claims, characterized in that the binder system in a proportion of 0.5 to 10 wt .-%, based on the weight of the refractory molding base material is included. Molding material mixture according to one of the preceding claims, characterized in that the binder system comprises a fatty acid ester as a solvent. Process for the production of a molded article for the foundry industry, characterized by the steps of: - providing a molding material mixture according to one of Claims 1 to 9 Shaping the molding material mixture into a molding, curing the molding by adding a curing catalyst. Method according to Claim 10 , characterized in that the curing catalyst is added in gaseous form. Method according to one of Claims 10 or 11 , characterized in that the curing is carried out substantially at room temperature. Moldings for the foundry industry, obtained by a method according to one of Claims 10 to 12 , Use of a molding after Claim 13 for metal casting.